Signals that regulate astroglial gene expression: induction of GFAP mRNA following seizures or injury is blocked by protein synthesis inhibitors

The purpose of this study was to develop methods for the consistent production of biofilms of S. mutans containing reporter gene fusions, and to examine the expression of genes involved in sucrose metabolism in adherent populations of this organism. Three strains of S. mutans harboring reporter gene fusions to the gene promoter regions of the gtfBC genes, ftf, and scrA were grown in a Rototorque biofilm fermenter in a tryptone-yeast extract-sucrose medium. Quasi-steady-state levels of reporter gene activity were measured after the biofilms were grown for either 48 hrs of 7 days. Also, induction of gene expression by the addition of sucrose to biofilm cells was monitored. Reporter gene activity was measurable from all gene fusion strains. This study (i) establishes the feasibility of doing detailed molecular and physiologic studies on immobilized populations of S. mutans, (ii) demonstrates that the polysaccharide synthesis machinery of S. mutans is differentially expressed in biofilms, and (iii) opens the way for a more detailed analysis of the environmental signals and signal transduction pathways governing the regulation of gene expression by S. mutans cells that are immobilized on a solid surface.     

Influence of salivary components and extracellular polysaccharide synthesis from sucrose on the attachment of Streptococcus mutans 6715 to hydroxyapatite surfaces

The adsorption of (3)H-labeled Streptococcus mutans 6715 cells to disks of hydroxyapatite (HA) was studied. The number of streptococci that adsorbed was logarithmically related to the concentration of cells available up to at least 2 x 10(8) per ml; equilibrium occurred within 45 min. Assay reliability was verified by direct scanning electron microscopic counts. Untreated HA disks exposed to buffered saline (PBS)-suspended streptococci at a concentration of 1.1 x 10(8) per ml absorbed 3.2 x 10(6) cells per cm(2); approximately 3% of the surface area was, therefore, occupied by adsorbed organisms. The presence of adsorbed salivary components on HA reduced the number of attaching S. mutans cells by half. When S. mutans cells were suspended in saliva to mimic conditions existing in the mouth, the number of streptococci adsorbing to saliva-treated HA was reduced more than 30-fold compared to untreated HA. Approximately one-half of the streptococci adsorbed to untreated or to saliva-treated HA disks could be desorbed over a 4-h period with 0.067 M phosphate buffer. S. mutans cells exposed to sucrose to permit extracellular polysaccharide synthesis before or during adsorption attached in fewer numbers to both saliva-treated and untreated HA than PBS-treated organisms. When S. mutans cells adsorbed on untreated HA were exposed to sucrose, fewer organisms could be desorbed; thus, in situ polysaccharide synthesis promoted their more firm attachment to untreated HA. However, when saliva-suspended streptococci were adsorbed to saliva-treated HA surfaces, exposure to sucrose before or subsequent to adsorption did not promote more firm attachment. Evidently, the powerful adherence-inhibiting and desorptive effects of salivary components overshadowed any promoting effects attributable to glucan synthesis from sucrose. Similarly, no differences were noted in the desorption of S. mutans cells from human teeth after exposure to sucrose, glucose, or PBS relative to a strain of Streptococcus mitis (S. mitior). Thus, no evidence was obtained to support the hypothesis that glucan synthesis from sucrose was essential for, or promoted, the attachment of S. mutans cells to HA surfaces exposed to saliva or to the smooth surfaces of human teeth.     

Sucrose and fructose have qualitatively different flavors to rats

Previous studies suggest that rats might be able to discriminate between sucrose and fructose, but no previous study has examined this possibility in much detail. Rats were conditioned to avoid either sucrose or fructose by injecting them with lithium chloride when they drank these substances. Control rats were given the same injections but were not exposed to either sugar during training. After training, the rats were given a choice of fructose vs. sucrose. Data from control rats provided information about the relative taste intensity of the sugars. If the sugars possess only a single gustatory quality, control rats should prefer the sweeter sugar; under this assumption, sucrose appears to be two-four times sweeter than fructose. The two sugars share a common taste because rats trained to avoid sucrose avoided fructose when the fructose concentration was much greater than the sucrose concentration. Nevertheless, the two sugars are discriminable because, when the apparent sweetness of the sugars was matched, rats showed a greater aversion to the sugar they were trained to avoid. Aversions to sucrose and fructose also generalized to maltodextrins, but sucrose may have a somewhat greater maltodextrin flavor than does fructose. It is proposed that the biological function of maltodextrin taste is to allow animals to sense the ratio of glucose to fructose in foods.     

Reduction in postprandial lipemia after walking: influence of exercise intensity

Whole-body thermogenesis, substrate utilization (open-circuit ventilated-hood system), and exogenous carbohydrate oxidation were evaluated in 10 healthy lean male volunteers (aged 27.8 +/- 2.5 years) for 6 hours after oral ingestion of 75 g naturally enriched fructose, glucose (both derived from corn starch), cane sugar, and a good digestible corn starch (all mixed with 400 mL water). The integrated areas under the glucose and insulin response curves above baseline were highest with glucose and starch, intermediate with sucrose, and lowest with fructose, whereas there were no significant differences in the integrated nonesterified fatty acid (NEFA) response between carbohydrates. The total increment in energy expenditure (EE) above baseline was similar with fructose (130 +/- 24 kJ/6 h) and sucrose (141 +/- 17 kJ/6 h), was higher with sucrose as compared with starch (108 +/- 24 kJ/6 h, P < .05) and glucose (94 +/- 20 kJ/6 h, P < .05), and tended to be higher with fructose as compared with glucose (P = .059). Both the increment in total carbohydrate oxidation (P < .05) and the increment in exogenous carbohydrate oxidation (P < .01) were significantly higher with fructose and sucrose compared with glucose and starch. The initial inhibition of lipid oxidation was higher with sucrose and fructose than with glucose and starch, whereas the integrated decrement in lipid oxidation over 6 hours was only higher with fructose compared with glucose and starch (P < .05). In conclusion, thermogenesis and substrate utilization vary considerably after ingestion of different types of carbohydrate in young lean males, indicating that the carbohydrate composition of the diet may have important consequences for energy and macronutrient balance.     

Specially designed sweeteners and food for diabetics--a real need?

In the first part of this study, the effect of four isocaloric mixed breakfast meals on the blood glucose and urinary glucose losses was tested in nine adult diabetics and in three healthy subjects, ages 60 to 75. Three of the test meals consisted of a base diet supplemented with applesauce sweetened with sucrose, fructose, or sorbitol. In the fourth test meal, the starch was increased together with saccharine. In the second part of the study, analyses for free glucose and sucrose in several timed food preparations, ordinary as well as food preparations specially designed for diabetics, were performed. The amount of sucrose equivalents (S(eg)) in one ordinary serving of the various products was estimated. No significant differences among sucrose, fructose, and sorbitol-containing meals with respect to the effect on the blood glucose level or on glucosuria were found. The saccharine-containing meal gave a significantly greater blood glucose increase at 60 min only. The amount of sucrose in ordinary marinated foods, such as herring, cucumber, and common beet was negligible. Water-packed fruits supplied one half of the amount of S(eq) or less, compared with fruits packed in sorbitol-sweetened syrup. The amount of S(eq) in the latter products as well as in fruits packed in unsweetened juice equalled that of the fleshy substance of ordinary sucrose-sweetened products. It was concluded that fructose or sorbitol has no advantages over sucrose, as regards the effect on blood glucose in well-regulated adult diabetics, and that it seems unnecessary to have specially sweetened foods designed for diabetics.     

Androgyny of physique in female track and field athletes

Long term feeding of a sucrose rich diet to rats is accompanied by a decreased glucose assimilation rate, despite high plasma insulin levels. Hyperinsulinism is at least partially based on a relative obesity, with increased amounts of abdominal- and retroperitoneal fat tissue, but unchanged total body weight compared to starch fed controls. The secretory pattern of insulin release was studied following glucose, arginine, fructose and sulfonylurea administration in the isolated perfused pancreas of sucrose and isocaloric starch fed rats. In addition, isolated islets of Langerhans were used to demonstrate the effects of glucose on insulin secretion and the incorporation of H-3 leucine into the proinsulin and insulin fraction of islet proteins. Following 11 mM glucose, the dynamics of insulin release in the isolated perfused pancreas of sucrose fed rats is characterized by a markedly elevated, late plateau-like response, usually seen only at higher glucose concentrations. Hyperinsulinism, as compared to starch fed controls, can also be demonstrated following arginine and the sulfonylurea HB-419, whereas fructose has no effect in the presence of low glucose concentrations. During incubation of the pancreatic islets, the hyperinsulinism in sucrose-, compared to starch fed rats, is more pronounced at 11 mM glucose than at 5.5 mM glucose. The incorporation of H-3 leucine into the proinsulin-insulin fraction of islet proteins in sucrose compared to starch fed rats, however, is significantly greater with glucose 5.5 mM than at high glucose level. In sucrose fed rats, secretion and biosynthesis of insulin thus appear to be elevated but closely linked only at physiological glucose concentration.     

Overexpression of an F-box Protein Gene Reduces Abiotic Stress Tolerance and Promotes Root Growth in Rice

As one of the largest gene families, F-box domain proteins have important roles in regulating various developmental processes and stress responses. In this study, we have investigated a rice F-box domain gene, MAIF1. The MAIF1protein is mainly localized in the plasma membrane and nucleus. MAIF1 expression is induced rapidly and strongly by abscisic acid (ABA) and abiotic stresses. MAIM expression is also induced in root tips by sucrose, independent of its hydrolytic hexose products, glucose and fructose, and the plant hormones auxin and cytokinin. Overexpression of MAIF1 reduces rice ABA sensitivity and abiotic stress tolerance and promotes rice root growth. These results suggest that MAIF1 is involved in multiple signaling pathways in regulating root growth. Growth restraint in plants is an acclimatization strategy against abiotic stress. Our results also suggest that MAIF1 plays the negative role in response to abiotic stress possibly by regulating root growth.     

Taste of sugars: Brief exposure single-stimulus behavioral method.

Used a brief exposure, single-stimulus test procedure to assess taste of sugars in 86 male Fischer rats. Ss were trained to sample the test solution immediately upon presentation. Intake was measured periodically for 10 min using fructose, glucose, or sucrose as a stimulus and water as a control. The stimulus-response functions and kinetics were different for the 3 sugars. Relative "sweetness" was predicted from the data to be sucrose > fructose > glucose. This prediction was confirmed by additional brief-exposure tests as well as by a 3-choice 24-hr test. Control experiments using a 2-choice 24-hr preference test showed that glucose was ingested preferentially. The brief exposure single-stimulus method appears to give a clearer indication of taste effectiveness than does the classical 2-choice 24-hr preference test. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prevention of progressive myopia

Changes in sugars and polyols content of fruits and leaves of three cultivar of peach, from fruit set to over maturity, have been studied. Sucrose, glucose, fructose and sorbitol were found both in leaves and in fruits. In fruits, inositol and galactose were also found but only in traces. Redhaven fruits show the greatest total sugars content (sorbitol included) (866 mg/g.d.m.)followed in order by Favorita and Prodigiosa ones (771 and 694 mg/g.d.m.) For Redhaven and Favorita fruits, at harvest matuity, the sugar present in greatest amount was sucrose followed in order by glucose, fructose and sorbitol. On the contrary, in Prodigiosa fruits the order was sucrose, sorbitol, fructose and glucose. In the leaves of three cultivar, the compound present in the greatest amount was sorbitol followed by sucrose, glucose and fructose. The sucrose decrease in leaves during fruit growth could confirm that the disaccharide is the main sugar transported from the leaves to the fruits.     

Occurrence and distribution of sucrose-metabolizing enzymes in oral streptococci

Specific growth rates, growth yields, and the level and cellular distribution of three sucrose-metabolizing enzyme activities were determined for seven oral streptococci (Streptococcus mutans strains E49, BHT, 10449, SL-1, and LM-7, S. sanguis 10558, and S. salivarius 25975). Cultures were grown in a fermentor at pH 6 with either 20 mM glucose or 10 mM sucrose. Generation times varied between 21 and 70 min. Whereas some strains grew 10 to 50% more slowly with sucrose than with glucose, others did not. Growth was always logarithmic, and the growth yields were similar. Glcosyl transferase (EC 2.4.1.5) was largely extracellular; in sucrose cultures it was appreciably lower, but no major shift to a cell-associated form was found. In glucose cultures, the activity varied between 4 and 140 IU per 6-liter culture. The glucan formed was mostly or exclusively water insoluble. Glcosyl transferase was stimulated weakly (60% or less) by various dextrans. Fructosyl transferase (EC 2.4.1.10) was primarily extracellular (except in glucose cultures of S. salivarius) and varied between 0 and 337 IU/culture. In S. salivarius, the extracellular fructosyl transferase was induced by sucrose. In all S. Mutans cultures, the total fructosyl transferase activity was lower after growth with sucrose. All strains had extra- and intracellular invertase (EC 3.2.1.26) activity. Total levels varied between 210 and 3,500 IU/culture. Less extracellular activity was present in sucrose cultures. Only S. salivarius had appreciable activity in the cellular particulate fraction. Invertase activity was significantly higher than the combined glucosyl and fructosyl transferase activities in all cultures.     

Epidemiological analysis defining concurrent outbreaks of Serratia marcescens and methicillin-resistant Staphylococcus aureus in a neonatal intensive-care unit

OBJECTIVE: To determine the plasma glucose and insulin responses of various doses of glucose, sucrose, fructose and white bread in normal human subjects. DESIGN: Plasma glucose and insulin were measured before and at various times after 8 subjects ate 13 different test meals in randomized order on separate days after an overnight fast. Test meals consisted of 500 ml of tea or water to which was added either nothing, 25, 50, or 100 g of glucose or sucrose, 25 or 50 g fructose, 50 g glucose plus 50 g fructose, or a 25, 50 or 100 g carbohydrate portion of white bread. The glycaemic (GI) and insulinaemic index (II) values of the sugars were calculated by expressing the incremental areas under the plasma glucose and insulin curves (AUC) after glucose, sucrose and fructose as a percentage of the respective AUC after white bread containing the same amount of carbohydrate. SETTING: University teaching hospital clinical nutrition centre. SUBJECTS: Lean, normal subjects (4 male, 4 female) 21-33 y of age. RESULTS: Plasma insulin responses increased nearly linearly as carbohydrate intake increased from 0 to 100 g, but glycaemic responses increased by only 68% and 38% as carbohydrate intake increased from 25 to 50 g and 50 to 100g, respectively. The GI and II values of glucose, 149+/-16 and 147+/-18, respectively, were significantly greater than those of bread (100; P<0.05), while the values for fructose, 16+/-4 and 22+/-3 were significantly less than those of bread (P<0.001). GI values did not differ significantly from II values. CONCLUSIONS: It is concluded that, in normal subjects, as carbohydrate intake is increased from 0 to 100 g, plasma insulin responses increase at a greater rate than plasma glucose responses. The insulinaemic responses elicited by glucose, sucrose or fructose are similar to those that would be expected from a starchy food with the same glycaemic index.     

Responses and physiological modifications of intestinal sucrase in rats fed diets containing various carbohydrates

Weaning rats were submitted during 3 months to complet and balanced diets where only glucidic constituent varied. They were sacrified when fed or after 16 h fasting. 1. The value of intestinal sucrose K(M) is higher in rats fed on glucose dietary than in rats fed on sucrose, fructose or glucose + fructose dietary. These modifications are independant of the states of digestion. 2. The V(MAX) is diversely influenced by the states of digestion: hydric diet increases the V(MAX) in animals fed on sucrose diet when intestinal repletion has the same effect in animals receiving glucose diet. Fructose diet decreases it irreversibility in both cases. 3. Growth of animals is sagging respectively in order from sucrose and glucose diets to glucose + fructose and fructose diets, then weight of organes is unaffected. It was noted that perirenal and epididymal fats are more abundant in rats nourished with glucose diet than with fructose diet. 4. The glucoregulation is correctly effectued in either starved or fed animals and shows an available adaptation of organism in energetic utilisation of various studied sugars. Plasmatic, hepatis and intestinal free fatty acids levels are constant and equal in all series of expements in spite of important variations of reverse fat.     

Growth and energetics of Leuconostoc mesenteroides NRRL B-1299 during metabolism of various sugars and their consequences for dextransucrase production

The metabolic and energetic properties of Leuconostoc mesenteroides have been examined with the goal of better understanding the parameters which affect dextransucrase activity and hence allowing the development of strategies for improved dextransucrase production. Glucose and fructose support equivalent specific growth rates (0.6 h-1) under aerobic conditions, but glucose leads to a better biomass yield in anaerobiosis. Both sugars are phosphorylated by specific hexokinases and catabolized through the heterofermentative phosphoketolase pathway. During sucrose-grown cultures, a large fraction of sucrose is converted outside the cell by dextransucrase into dextran and fructose and does not support growth. The other fraction enters the cell, where it is phosphorylated by an inducible sucrose phosphorylase and converted to glucose-6-phosphate (G-6-P) by a constitutive phosphoglucomutase and to heterofermentative products (lactate, acetate, and ethanol). Sucrose supports a higher growth rate (0.98 h-1) than the monosaccharides. When fructose is not consumed simultaneously with G-1-P, the biomass yield relative to ATP is high (16.8 mol of ATP.mol of sucrose-1), and dextransucrase production is directly proportional to growth. However, when the fructose moiety is used, a sink of energy is observed, and dextransucrase production is no longer correlated with growth. As a consequence, fructose catabolism must be avoided to improve the amount of dextransucrase synthesized.     

Comparative quantitative analysis of sucrose and related compounds using ion exchange and reverse phase chromatographic methods

Two analytical methods of sugar determination, namely ion exchange chromatography on an anionic resin coupled with electrochemical detection, and reverse phase chromatography on Nucleosil-NH2 resin equipped with a light scattering detector were tested and compared as regards their rapidity, sensitivity and accuracy with sucrose, fructose, glucose, raffinose, maltose, arabinose, fucose, rhamnose and xylose. Excellent resolution and highly reproducible results were obtained in both cases. Greater sensitivity up to the picomolar range was possible however only with ion exchange chromatography. Reverse phase chromatography was successfully applied to the time course of sucrose hydrolysis under chemical (acid) and enzymatic (invertase) conditions. The hydrolysis was monitored by determining sucrose degradation and the corresponding formation of glucose and fructose.     

Violent versus nonviolent stalkers

The sgp gene from Streptococcus mutans has been previously isolated, characterized, and demonstrated to encode a G-protein. In order to investigate the function of this gene, a novel antisense RNA strategy was developed. Expression of sgp antisense RNA in Escherichia coli led to transient inhibition of growth. In addition, sgp antisense RNA expression in S. mutans resulted in decreased growth under environmental stress conditions (44 degrees C, acidic pH, and high osmolarity). Therefore, these results suggest that the sgp gene plays a role in modulating the stress responses of S. mutans. This approach could be applicable for investigating the function of essential genes in other organisms for which mutants are not available.     

Structural aspects of glucans formed in solution and on the surface of hydroxyapatite

Streptococcus mutans glucosyltransferases (GtfB, -C, and -D) and their products formed from sucrose, glucans, play an essential role in the pathogenesis of dental caries. Enzymatically active Gtf is found in whole human saliva (solution), and incorporated into the salivary pellicle that is formed on teeth in vivo (surface). GtfB glucans are predominantly 1,3-linked; however, surface-formed glucans from GtfB contain greater amounts of 3-linked glucose than glucans formed in solution. In contrast, the major linkage of glucans formed on the surface by GtfB in the presence of sucrose and starch hydrolysates in 4-linked glucose. GtfC-derived glucans in solution have a major linkage of 6-linked glucose, while surface-formed glucans from the same enzyme have 3-linked glucose as the major linkage. GtfD glucans formed either in solution or on the surface are predominantly 1,6-linked; however, surface-formed glucans contain more 6-linked glucose than solution-formed glucans. Digestion with the glucanohydrolases mutanase and dextranase shows differences in susceptibility among glucans formed either in solution or on the surface by each of the Gtf enzymes, and differences are also seen in the soluble end products from these digestions. Our results show that the same Gtf enzyme can form structurally distinct glucans in solution and on a surface. These observations are important in the study of naturally occurring microbial films.     

Analysis of the exudate produced by Streptococcus mutans SL-1 colonies of sucrose-containing agar media

The watery exudate produced by Streptococcus mutans SL-1 colonies on sucrose-containing agar media was found to contain about 7% (wt/vol) of a water-soluble, branched dextran, 4% sucrose, and smaller (less than 1%) amounts of fructose, Folin-phenol-positive material, and lactic acid.     

Intracellular alpha-amylase of Streptococcus mutans

Sequencing upstream of the Streptococcus mutans gene for a CcpA gene homolog, regM, revealed an open reading frame, named amy, with homology to genes encoding alpha-amylases. The deduced amino acid sequence showed a strong similarity (60% amino acid identity) to the intracellular alpha-amylase of Streptococcus bovis and, in common with this enzyme, lacked a signal sequence. Amylase activity was found only in S. mutans cell extracts, with no activity detected in culture supernatants. Inactivation of amy by insertion of an antibiotic resistance marker confirmed that S. mutans has a single alpha-amylase activity. The amylase activity was induced by maltose but not by starch, and no acid was produced from starch. S. mutans can, however, transport limit dextrins and maltooligosaccharides generated by salivary amylase, but inactivation of amy did not affect growth on these substrates or acid production. The amylase digested the glycogen-like intracellular polysaccharide (IPS) purified from S. mutans, but the amy mutant was able to digest and produce acid from IPS; thus, amylase does not appear to be essential for IPS breakdown. However, when grown on excess maltose, the amy mutant produced nearly threefold the amount of IPS produced by the parent strain. The role of Amy has not been established, but Amy appears to be important in the accumulation of IPS in S. mutans grown on maltose.