Sugars In Response Research Articles

A tong-like fluorescence sensor for metal ions: perfect conformational switch of hinge sugar by pyrene stacking

Carbohydrates are among the potential materials for molecular devices, since they are abundant natural resources. However, their rigidity has restricted their use for movable devices. Hinge sugars, 2,4-diamino-2,4-dideoxy-xylopyranosides, shed light on the use of carbohydrates as movable components, as demonstrated by the motion by which all four equatorial substituents can change to an axial orientation in synchronization with a chelation-driven 4C1-1C4 ring flip. In this study, we synthesized a tong-like metal ion sensor, 1,3-di-O-pyrenylmethylated hinge sugar (1), and its model compound, methyl 2,4-di-O-pyrenecarbonyl-xylopyranoside (2), to extend the abilities of hinge sugars as molecular components. From observations of the solvent-dependent conformational and fluorescent behavior of 2, we found that the pyrene stacking assists the 1C4 formation of xylopyranoside by 1.7 kcal mol(-1). We also found that compound 1 produced excimer fluorescence by chelation to Pt2+, Zn2+, Cd2+, Mg2+ or Mn2+, and unexpectedly by addition of acids. 1H NMR measurements ascribed this behavior to the 4C1-1C4 ring flip of hinge sugar in response to chelation or protonation at N2, and revealed rapid and perfect 1C4 formation in the case of Zn2+. These findings will extend the scope of hinge sugars as movable components.

598 Drought Stress Affects Carbohydrate Partitioning in Three Species of Herbaceous Perennials

Drought stress durations of 2, 4, and 6 days were imposed on Boltonia asteroides `Snowbank', Eupatorium rugosum, and Rudbeckia triloba to determine the effects on carbohydrate partitioning in the plant. Drought stress was imposed on 19 Sept. 1997 on 1.9-L containerized plants. Plants were planted in the field the day following release from stress. Crown and leaf samples of the three species were collected 21, 23, 25 Sept. 1997 and 30 Jan. and 4 May 1998 and were analyzed for low molecular weight sugars and fructans. The species differed in the time it took for longer chain fructans to break down to shorter chain fructans and low molecular weight sugars (glucose, fructose). The drought tolerant Boltonia and Rudbeckia had shifts from longer chain to shorter chain fructans by day 4 of stress. Boltonia had a change in carbohydrate partitioning in the leaf tissue, while Rudbeckia had a change in crown tissue carbohydrate partitioning. Eupatorium did not have a shift in longer chain fructans to shorter chain fructans in crown tissue until day six of stress. The slower shift from longer chain fructans to shorter chain fructans by Eupatorium, compared to Boltonia and Rudbeckia, could explain the lack of drought tolerance of Eupatorium. The shift from high molecular weight sugars to low molecular weight sugars suggests that the higher molecular weight sugars broke down to lower molecular weight sugars in response to drought stress.

Carbohydrate levels among winter wheat cultivars varying in freezing tolerance and snow mold resistance during autumn and winter

The LT50 values and soluble carbohydrate levels in wheat (Triticum aestivum L.) crowns and leaves were monitored throughout autumn and winter in cultivars varying in freezing tolerance and snow mold resistance during 1993/1994 and 1994/1995 in the field at Sapporo, Japan. During the first stage of hardening, from sowing to mid‐November, the pattern of accumulation of mono‐ and disaccharides was similar for all cultivars. During the second stage of cold hardening, from mid‐November to mid‐December, the greatest accumulation of mono‐ and disaccharides, without a corresponding increase in fructan, was observed among the freezing‐tolerant cultivars; and levels of simple saccharides rapidly decreased under snow cover. Conversely, levels of mono‐ and disaccharides in snow mold‐resistant cultivars were less than 70% of those in freezing‐tolerant cultivars before snow cover and maintained low levels throughout winter, while polysaccharide levels in snow mold‐resistant cultivars were about 120% of those in freezing‐tolerant cultivars in December. Sugar metabolism during the winter was examined using 18 cultivars in 1994/1995. LT50 values were correlated to the greatest extent with total mono‐ and disaccharide and fructan content among wheat cultivars excluding snow mold‐resistant cultivars in December. Snow mold‐resistant cultivars tended to metabolize carbohydrates more slowly until the end of the snow cover period. This result suggested that the enzymatic metabolism of the synthesis of sugars and the conversion of fructan to cryoprotective sugars in response to low temperatures, especially subzero ones, might be different between the two contrasting types in resistance to winter stress.

RELATIONSHIP BETWEEN GASTRIC MUCUS SYNTHESIS, SECRETION AND SURFACE GEL EROSION MEASURED IN AMPHIBIAN STOMACH IN VITRO

1. The layer of adherent mucus that protects the surface of the stomach reflects a dynamic balance between biosynthesis of glycoprotein, secretion of preformed mucus and erosion of the adherent gel layer. The present study is the first in which all these processes have been measured concomitantly and was undertaken to define interrelationships between the three parameters. 2. A chambered sac preparation of amphibian gastric mucosa is described. Biosynthesis was determined by specific incorporation of radiolabelled sugars into purified glycoprotein. Mucus secretion was determined by measuring the thickness of the adherent gel and erosion of the surface layer was assessed from the appearance of soluble mucin in the luminal solution. 3. 16,16-Dimethyl-prostaglandin (PG) E2 stimulated glucosamine incorporation by 10-fold, but did not alter the rate of incorporation of galactose. There was a rapid two-fold increase in the thickness of the adherent mucus layer but no change in the rate of erosion. Dibutyryl-cAMP also stimulated mucus release but, unlike PG, increased glycoprotein labelling by galactose. 4. Both distention or the application of a cholinergic agonist increased adherent mucus thickness. Stimulation of mucus release in response to carbachol was accompanied by a decrease in glycoprotein labelling by galactose. In contrast, the adrenergic agent noradrenaline decreased secretion but did not influence labelling. 5. These results indicate that biosynthesis and secretion of gastric mucus are subject to differential regulation. Moreover, the profile of incorporation of sugars in response to secretagogues also differs, indicating the need for caution when interpreting effects on glycoprotein biosynthesis.

Enrichment in Specific Soluble Sugars of Two Eucalyptus Cell-Suspension Cultures by Various Treatments Enhances Their Frost Tolerance via a Noncolligative Mechanism.

A cell-suspension culture obtained from the hybrid Eucalyptus gunnii/Eucalyptus globulus was hardened by exposure to lower temperatures, whereas in the same conditions cells from a hybrid with a more frost-sensitive genotype, Eucalyptus cypellocarpa/Eucalyptus globulus, were not able to acclimate. During the cold exposure the resistant cells accumulated soluble sugars, in particular fructose and sucrose, with a limited increase in cell osmolality. In contrast, the cell suspension that was unable to acclimate did not accumulate soluble sugars in response to the same cold treatment. To an extent similar to that induced after a cold acclimation, frost-hardiness of the cells increased after a 14-h incubation with specific soluble sugars such as sucrose, raffinose, fructose, and mannitol. Such hardening was also observed for long-term cultures in mannitol-enriched medium. This cryoprotective effect of sugars without exposure to lower temperatures was observed in both the resistant and the sensitive genotypes. Mannitol was one of the most efficient carbohydrates for the cryoprotection of eucalyptus. The best hardiness (a 2.7-fold increase in relative freezing tolerance) was obtained for the resistant cells by the cumulative effect of cold-induced acclimation and mannitol treatment. This positive effect of certain sugars on eucalyptus freezing tolerance was not colligative, since it was independent of osmolality and total sugar content.

The role of octopamine in handling and exercise-induced hyperglycaemia and hyperlipaemia in Acheta domesticus

House crickets, Acheta domesticus, are different from related Orthoptera in that they give a hyperglycaemic and hyperlipaemic response to handling stress and to injections of octopamine instead of either hyperglycaemia (cockroaches) or hyperlipaemia (locusts). The rapid elevation of both lipids and sugars in response to handling stress is probably due to octopamine released into circulation from the head, because the response was eliminated with head ligation. Exercise stress caused a rapid hyperglycaemia and a delayed hyperlipaemia; we suggest that the rapid sugar elevation was due to release of octopamine from the corpora cardiaca and that the delayed elevation of lipids was due to the release of adipokinetic hormone. The age related depletion of fat body reserves through oögenesis appeared to lower the capacity of the cricket to mobilize sugar in response to stress.

Boron fertilization and carbohydrate relations in mycorrhizal and nonmycorrhizal shortleaf pine.

Eight-week-old shortleaf pine seedlings (Pinus echinata Mill.) with and without ectomycorrhizae formed by Pisolithus tinctorius were treated for two to eight weeks with 25 microg borate ml(-1) solution applied either to the soil, or as a foliar spray, or in both ways. Control seedlings were fertilized only with modified Hoagland's solution containing 0.03 microg ml(-1) borate. Five sugars (pinitol, fructose, glucose, myoinositol and sucrose) were quantitated in both mycorrhizal and nonmycorrhizal roots by gas-liquid chromatography. Fertilization with boron increased the total carbohydrate content of mycorrhizal roots except in seedlings receiving foliar applications of boron. Foliar + soil fertilization yielded a 24% increase in total carbohydrates in mycorrhizal roots, whereas foliar fertilization alone decreased the total carbohydrate content. Carbohydrate content of nonmycorrhizal roots was significantly increased only by soil fertilization with boron. Individual sugars were affected less by boron fertilization in nonmycorrhizal roots than in ectomycorrhizal roots. However, significant increases in sugars in response to boron fertilization were observed in both ectomycorrhizal and nonmycorrhizal plants.

Taste and smell in disease (second of two parts).

Disorders of taste and smell are common occurrences that can lead to modifications of dietary habits that may in turn exacerbate disease states or nutritional deficiencies. In addition, they are often nagging problems that diminish the quality of life. Such disorders can result from a range of disease states, pharmacologic and surgical intervention, aging, radiation, and environmental exposure. A search for the pathogenetic mechanism should include the determination of possible (1) local injury from physical or chemical causes, (2) damage to neural projections, (3) disturbance of the cycle of regeneration of chemoreceptors resulting from general malnutrition, disease agents, metabolic disturbances, drugs, or radiation, and (4) alteration in the saliva or fluids bathing the olfactory mucosa by drugs or metabolic agents. Viral infections, normal aging, head injuries, and nasal obstructions are the most common causes of smell disorders. Drugs are common offenders in taste dysfunction. Chemosensory disorders frequently remit when concomitant medical conditions are treated or offending drugs removed, although full recovery may take several months. Considerable research is now under way in this area, and it is to be hoped that we will soon have a better understanding of how to diagnose and treat these common disorders.

Effect of IAA on Growth and Soluble Cell Wall Polysaccharides Centrifuged from Pine Hypocotyl Sections

Auxin-induced elongation and cell wall polysaccharide metabolism were studied in excised hypocotyl sections of ponderosa pine (Pinus ponderosa) seedlings. Sections excised from hypocotyls of ponderosa pine elongate in response to the addition of auxin. The neutral sugar composition of the extracellular solution removed from hypocotyl sections by centrifugation was examined. In cell wall solution from freshly excised sections, glucose, galactose, xylose, and arabinose make up more than 90% of the neutral sugars, while rhamnose, fucose, and mannose are relatively minor components. The neutral sugar composition of the polysaccharides of the pine cell wall solution is both qualitatively and quantitatively similar to that of pea. Following auxin treatment of pine hypocotyls, the neutral sugar composition of the cell wall changes; glucose, xylose, rhamnose, and fucose increase by nearly 2-fold relative to controls in buffer without auxin. These changes in neutral sugars in response to auxin treatment are similar to those found in pea, with the exception that in pea, rhamnose levels decline in response to auxin treatment.

Characteristics of Heterotrophic Growth in the Blue-Green Alga Nostoc sp. Strain Mac

The blue–green alga Nostoc sp. strain Mac was grown heterotrophically in the dark on glucose and fructose. Cell composition was similar under photoautotrophic and hetero-trophic growth conditions and the efficiency of cell synthesis, in most cases, was similar to values obtained with other heterotrophic micro-organisms. Differences were seen in growth on the two sugars in response to sugar concentration and nitrogen source, and in the efficiency of cell synthesis in minimal medium, which indicated differences in the metabolism of the two sugars by the alga. Heterotrophic growth was stimulated by casein hydrolysate and dim light. Both effects were additive, indicating at least two different rate-limiting steps in the heterotrophic metabolism of the alga. Casein hydrolysate acted as a bulk nitrogen source for the alga and the response to dim light showed a chlorophyll a-like action spectrum.

The Effect of Dialysis on the Carbohydrate Intolerance of Chronic Renal Failure

Oral glucose tolerance tests were performed in relation to hemodialysis and peritoneal dialysis. The results have shown lower fasting blood sugars and considerably improved glucose tolerance in the immediate post-dialysis period. Both basal serum insulin levels and the rise following glucose were enhanced after hemodialysis. On the other hand, peritoneal dialysis resulted in lower insulin levels. Although there were no consistent changes in the elevated growth hormone concentrations after either dialysis, higher levels were more frequently observed in patients undergoing peritoneal dialysis. In all subjects, plasma-free fatty acids supressed promptly after glucose administration. Following hemodialysis, there was a greater fall in blood sugar in response to tolbutamide, but his was not associated with an enhanced insulin response. Progressive improvement in glucose tolerance occurred in one subject tested serially after renal transplantation. The causes and significance of these metabolic abnormalities in uremic patients are discussed.

Effect of atropine on blood pressure of patients with mental and emotional disease.

CONCOMITANT with the psychological signs and symptoms of schizophrenia are many physiological disturbances. These, among others, include vasomotor changes, excessive salivation, cardiovascular dysfunction, and pupillary abnormalities, which clearly implicate the autonomic nervous system. Much excellent research * has more directly involved both the sympathetic and the parasympathetic components of the autonomic system. Claims are registered that the reactivity of the autonomic system is normal 5 as measured by known methods or that it is sluggish.† The decreased reactivity of the schizophrenic to cold is ascribed to the diminished secretion of epinephrine and the deficient or disordered output of adrenocortical factors, which similarly accounts for the diminished elevation of the blood sugar in response to stress. 3 There is a tendency to emphasize either the sympathetic nervous system 6 or the parasympathetic nervous system.‡ In the acute phases sympathetic predominance does appear to be present.§ Nevertheless, injections of blood from excited schizophrenics

THE COMPARATIVE EFFECTS OF COMA DOSES OF AMORPHOUS INSULIN ADMINISTERED INTRAVENOUSLY AND SUBCUTANEOUSLY TO PSYCHOTIC PATIENTS

1. In a group of 13 schizophrenic patients the blood sugar fell more promptly in response to coma doses of amorphous insulin given intravenously than to those given subcutaneously. 2. The fall in blood sugar in response to coma doses of insulin given intravenously occurs at about the same rate as in response to small doses—e.g., 10 units. In the latter case the blood sugar returns to normal values rapidly, whereas in the former it stays low for a prolonged time, so that coma ensues. 3. The only practical advantage of the intravenous administration of insulin is the shortening of the pre-coma period. 4. There was no appreciable difference in the coma doses required between the two methods of administration. 5. There was no significant difference in the complications resulting from the two methods of injection. 6. Spontaneous emergence from coma produced by intravenous insulin is rare.

Time Curve of Insulin Action in the Depancreatized Dog

Scott and Dotti1 have made an extended study of blood sugar lowering effects of insulin given subcutaneously to rabbits. They have concluded that the results, when expressed as the fraction of sugar removed, are independent of the initial blood sugar while the absolute value of blood sugar after a given time interval or the absolute value of the fall in blood sugar is dependent on the initial value. It is, therefore, the fraction removed and not any of the absolute values which is related only to the insulin dose. They have studied the effect after one given time interval which is empirically chosen. Observations taken at later time intervals cannot be used because the blood sugar under their conditions tends to return too early towards the initial level.Elsewhere2 we have stated that after pancreatectomy in the dog the blood sugar in response to intravenous insulin falls continuously for a much longer period of time than in the normal animal. The factor which tends to early return towards the initial lev...