Viscous Gum Research Articles

Alginate Nanoparticles for Drug Delivery and Targeting.

Nanotechnology refers to the control, manipulation, study and manufacture of structures and devices at the nanometer size range. The small size, customized surface, improved solubility and multi-functionality of nanoparticles will continue to create new biomedical applications, as nanoparticles allow to dominate stability, solubility and bioavailability, as well controlled release of drugs. The type of a nanoparticle, and its related chemical, physical and morphological properties influence its interaction with living cells, as well as determine the route of clearance and possible toxic effects. This field requires cross-disciplinary research and gives opportunities to design and develop multifunctional devices, which allow the diagnosis and treatment of devastating diseases. Over the past few decades, biodegradable polymers have been studied for the fabrication of drug delivery systems. There was extensive development of biodegradable polymeric nanoparticles for drug delivery and tissue engineering, in view of their applications in controlling the release of drugs, stabilizing labile molecules from degradation and site-specific drug targeting. The primary aim is to reduce dosing frequency and prolong the therapeutic outcomes. For this purpose, inert excipients should be selected, being biopolymers, e.g. sodium alginate, commonly used in controlled drug delivery. Nanoparticles composed of alginate (known as anionic polysaccharide widely distributed in the cell walls of brown algae which, when in contact with water, forms a viscous gum) have emerged as one of the most extensively characterized biomaterials used for drug delivery and targeting a set of administration routes. Their advantages include not only the versatile physicochemical properties, which allow chemical modifications for site-specific targeting but also their biocompatibility and biodegradation profiles, as well as mucoadhesiveness. Furthermore, mechanical strength, gelation, and cell affinity can be modulated by combining alginate nanoparticles with other polymers, surface tailoring using specific targeting moieties and by chemical or physical cross-linking. However, for every physicochemical modification in the macromolecule/ nanoparticles, a new toxicological profile may be obtained. In this paper, the different aspects related to the use of alginate nanoparticles for drug delivery and targeting have been revised, as well as how their toxicological profile will determine the therapeutic outcome of the drug delivery system.

An arabinogalactan with anti-ulcer protective effects isolated from Cereus peruvianus

A type I arabinogalactan (CPP) was isolated from the viscous gum exuded by Cereus peruvinus (Cactaceae). It contained arabinose, galactose, galacturonic acid, and rhamnose in a 15:66:6:13 molar ratio and had M w 9 × 10 5 g mol −1. Methylation analysis and 13C NMR spectroscopy indicated that CPP is composed of a (1 → 4)-linked β- d-Gal p main-chain with substituents of α- l-Ara f at O-2, O-3 and O-6, which are in turn substituted at O-2, O-3, and O-2,3. These are probably linked to O-4 of some rhamnosyl units of a type I rhamnogalacturonan ( RG1). The main chain is formed by repeating (1 → 4)-α- d-Gal pA-(1 → 2)-α- l-Rha p groups. The methylation analysis suggested the presence of (1 → 3)-linked β-Gal p structures, perhaps linked to the (1 → 4)-linked β- d-Gal p backbone. CPP significantly inhibited ethanol-induced gastric lesions in rats at an ED 50 of 49 mg kg −1, indicating that it has a gastroprotective effect. The gastric lesion inhibition by CPP suggests a potential use of this polysaccharide, or the crude plant extract, in phytotherapy.

CHEMICAL CONSTITUENTS FROM THE LEAVES OF SANDORICUM KOETJAPE

CHEMICAL CONSTITUENTS FROM THE LEAVES OF SANDORICUM KOETJAPE

Guar gum does not impair the absorption and utilization of dietary nitrogen but affects early endogenous urea kinetics in humans

Viscous gums enhance viscosity in the upper gastrointestinal lumen, quickly disturbing motility and promoting fluid secretion. We sought to determine whether guar gum could acutely affect the absorption and utilization of dietary nitrogen and whether these luminal effects could also perturb the kinetics of urea. We studied the short-term effect of adding 1% of highly viscous guar gum to a (15)N-labeled protein meal (30 g soy protein isolate in 500 mL water) during the postprandial phase in humans. The effects on bioavailability were studied by using the [(13)C]glycine breath test (to assess gastric emptying) and (15)N enrichment in plasma amino acids (for systemic amino acid bioavailability). The kinetics of dietary and endogenous urea were assessed in plasma and urine. Guar gum modulated the gastric emptying kinetics of the liquid phase of the meal slightly (P < 0.05), but had no significant effect on either the systemic appearance of dietary amino acids or plasma and urinary dietary urea kinetics. Without significantly affecting plasma urea concentrations, guar gum reduced by approximately 40% the urinary excretion of endogenous urea for the first 2-h period after the meal (P < 0.01), although endogenous urinary excretion was similar at later stages. Guar gum did not significantly affect the bioavailability or utilization of dietary protein. We showed an early effect of guar gum on endogenous urea kinetics, which most probably arose from very early, short-term stimulation of the intestinal disposal of endogenous urea, at the expense of its urinary excretion.

Malaise can condition avoidance of high-viscosity fluids

Previous researchers have assumed that malaise-inducing drugs condition aversions to tastes more readily than to textural stimuli. The present report shows that rats given a single injection of lithium chloride after they have sampled a viscous fluid, subsequently showed greater avoidance of that fluid than did control rats. Rats learned this response even when the lithium chloride injection was given 60 min after they sampled the viscous fluid. The generalization gradient for viscous fluids is apparently very broad, because rats trained to avoid 11 or 95 cp fluids subsequently avoided 11 and 95 cp fluids to a similar degree. Nevertheless, this avoidance is based on textural cues because rats injected with lithium chloride after ingesting one viscous fluid subsequently avoided a wide variety of viscous fluids, including those made from carbohydrate polymers (algin, guar, xanthan), a modified carbohydrate (methyl cellulose), and a protein (methyl cellulose). However, the flavors of viscous gums may influence texture aversion.

Precursor route to ethenyl-substituted polyacetylenes: synthesis of homopolymers of o-trimethylsilyl-ethers of 1-alkyl and 1-aryl substituted but-3-yn-1-ols. Desilylation, dehydration and pyrolysis to conducting films

Poly( o-trimethylsilyl-but-3-yn-1-ols) were from trimethylsilyl ethers of RCH(OH)CH 2CCH (R=H, Me, C 6H 5 or CH=CHCH 3) via Ziegler-Natta polymerization (Fe(acac) 3/AlEt 3 in toluene, 20–35 °C) of the terminal triple bond. The polymers were obtained as yellow amorphous solids (10–23%, polymer with R=H was a viscous gum) with atactic microstructure ( 13C NMR), soluble in apolar solvents. The polymer from the monomer with R=CH=CHCH 3 could be desilylated quantitatively with potassium fluoride. Elimination of water at 200–250 °C from films of this deprotected polymer gave a semiconducting material (10 −4 S/cm) after activation with iodine. Heating the undoped film for 10–20 min at 650 °C in nitrogen atmosphere gave an intrinsically conducting brittle film (10 −2 S/cm with silvery-black lustre. Activation with iodine enhanced the conductivity to 10 1−10 2 S/cm. High conductivity was not persistent in ambient atmosphere.

Chemoreception for an insoluble nonvolatile substance: starch taste?

Substances that are insoluble in both water and lipids, such as starch, are commonly assumed to be tasteless. Starch was suspended in water with a viscous gum. Rats given a choice of fluid containing starch and the same fluid without starch consistently preferred fluids containing starch. Rats were able to detect as little as 0.5% starch from several species of plants (corn, rice, wheat, and potato). In contrast, rats ignored comparable concentrations of cellulose suspended in water. Rats were also capable of choosing the fluid containing higher levels of starch when given a choice of 1 vs. 2% starch or 0.5 vs. 1% starch. This ability to detect starch did not appear to be mediated by salivary alpha-amylase because 1) raw starch is highly resistant to hydrolysis by salivary amylase, 2) starch preference was not correlated with the susceptibility of the starch to hydrolysis by salivary amylase, and 3) starch preference was not blocked by partial or extensive desalivation. Attempts to extract impurities with either organic solvents or water did not provide any evidence that such impurities contribute to starch preference. These experiments point to a seemingly novel form of chemoreception that could be useful to animals that need to identify starch-rich foods.

Three Species of House Spiders First Recorded in Kansas: Dysdera crocata (Dysderidae), Scytodes thoracica (Scytodidae), and Cheiracanthium mildei (Clubionidae)

Three Species of House Spiders First Recorded in Kansas: Dysdera crocata (Dysderidae), Scytodes thoracica (Scytodidae), and Cheiracanthium mildei (Clubionidae)

4737718 Magnetic resonance imaging apparatus including a bird-cage r.f. coil

Between S/P mole ratios of 0·75 and 3·50 in the phosphorus-sulphur system, quenching of melts gave completely amorphous compositions for S/P ratios of 1·0 and 1·25 (both viscous gums) and 3·0 and 3·5 (both brittle glasses). 31P nuclear-magnetic-resonance (n.m.r.) spectra of the viscous liquids (heated sufficiently to avoid line broadening) show that, for S/P = 1·0, 59 per cent of the total phosphorus and, for S/P = 1·25, 33 per cent of the total phosphorus is present as the P4S3 bird-cage molecule. On the other hand, viscosity data indicate that macromolecules are present in melts for which S/P > ca. 1·8. The rates of dissolution of the various crystalline, amorphous and partially amorphous phosphorus sulphides in n-butanol were measured and are interpreted on a per-unit-area basis. N.m.r. spectra of the solutions resulting from reaction of the butanol with the phosphorus sulphides show the presence of many phosphorus compounds.

Plasma enteroglucagon and small bowel cytokinetics in rats fed soluble nonstarch polysaccharides

The influence of dietary fiber on plasma glucagon and enteroglucagon (EG) and on ileal crypt cell production rate (CCPR) was assessed in the rat. A fiber-free semisynthetic diet and diets containing insoluble cellulose, Na-carboxymethylcellulose (CMC), guar gum, pectin, gum arabic, methylcellulose (MC), and hydroxypropylmethylcellulose (HPMC) at 10 g/100 g were fed for 14 d. Animals given soluble polysaccharides had plasma EG levels significantly higher than animals given insoluble cellulose, but only those fed the most viscous gums showed evidence of increased mucosal cell proliferation in the distal ileum. It was concluded that viscous nonfermentable polysaccharide gums stimulate the release of EG in the rat by slowing the absorption of nutrient, whereas the nonviscous polysaccharide gum arabic, or its breakdown products, probably directly stimulate mucosal endocrine cells. The failure of gum arabic to stimulate CCPR despite increased plasma EG indicated that EG alone is not a sufficient stimulus for increased mucosal cell proliferation.

Effects of dietary oat bran and diabetes on plasma and caecal volatile fatty acids in the rat

Diets high in plant fibre, particularly viscous gums, are of potential benefit in the control of diabetes in man. This study compares the effects of oat bran, one such fibre preparation, with purified cellulose on volatile fatty acid metabolism in rats fed a high carbohydrate diet. Concentrations of total volatile fatty acids were significantly higher both in hepatic portal venous plasma and caecal contents of rats fed oat bran. Major differences were also found in the relative contributions of individual acids with proportionately less acetate and more propionate and butyrate in these animals compared with rats fed cellulose. In rats fed a standard laboratory diet, diabetes induced by streptozotocin produced a sustained increase in caecal and hepatic portal venous concentrations of acetate, propionate and butyrate. Because of the high simple carbohydrate content of the experimental diet, the tolerance of diabetic rats for the bran and cellulose diets was poor and no differences in VFA metabolism were observed after 24 hr of diabetes. It is concluded that volatile fatty acid concentrations were in proportion to the probable digestibility of the source of dietary fibre and are significant metabolic fuels liable to altered metabolism by insulin insufficiency.

Icosahedral carboranes. XIX. Preparation of linear trifluoropropyl‐substituted polycarboranylenesiloxanes

AbstractA series of linear trifluoropropyl‐substituted polycarboranylenesiloxanes with molecular weights between 3,500 and 13,000 has been prepared by the tetramethylguanidine–sulfuric acid‐catalyzed condensation of various silanol‐terminated monomers as well as by simple hydrolytic condensation of m‐B10H10C2(SiMePfOSiMePfCl)2 and B5H5C2‐(SiMePfCl)2 (where Pf = CH2CH2CF3). The polymers containing the C2B5H7 and C2B10H12 carboranes range from hard glasses to viscous gums and rubbers, are more thermally stable than fluorinated silicones with comparable resistance to solvents, and are potentially useful as high‐temperature fuel tank sealants.

The role of wheat flour pentosans in baking. II.—Effect of added flour pentosans and other gums on gluten‐starch loaves

AbstractLoaves made from gluten and starch alone were inferior in volume and texture to loaves made with the addition of flour solubles. The effect of flour solubles was destroyed by enzymes which degrade polysaccharides but was unaffected by an active protease.Other viscous gums were tested for effectiveness in improving the volume of gluten‐starch loaves. A wide range was effective, but some had no effect.

Studies on phosphorus sulphides

Between S/P mole ratios of 0·75 and 3·50 in the phosphorus-sulphur system, quenching of melts gave completely amorphous compositions for S/P ratios of 1·0 and 1·25 (both viscous gums) and 3·0 and 3·5 (both brittle glasses). 31P nuclear-magnetic-resonance (n.m.r.) spectra of the viscous liquids (heated sufficiently to avoid line broadening) show that, for S/P = 1·0, 59 per cent of the total phosphorus and, for S/P = 1·25, 33 per cent of the total phosphorus is present as the P 4S 3 bird-cage molecule. On the other hand, viscosity data indicate that macromolecules are present in melts for which S/P > ca. 1·8. The rates of dissolution of the various crystalline, amorphous and partially amorphous phosphorus sulphides in n-butanol were measured and are interpreted on a per-unit-area basis. N.m.r. spectra of the solutions resulting from reaction of the butanol with the phosphorus sulphides show the presence of many phosphorus compounds.

Rubberlike Products from Linear Polyesters

Abstract The polymers which result from the condensation of dibasic acids with propylene glycol are viscous gums which can be vulcanized to rubberlike products. In the unpigmented condition these rubbers are quite weak, but when reinforced with suitable pigments their strength and elongation compare favorably with other synthetic rubbers. Because polyesters of known structure and molecular weight can be easily synthesized, these polymers are useful for the study of the relations between structure and properties in rubberlike materials in general. Factors affecting tensile strength, oil resistance, brittle temperature, and stability are discussed. The development of rubberlike products from linear polyesters was announced in a short news article more than three years ago, but a detailed description of their preparation and physical properties has not been published. The object of this paper is to review these properties. However, the paper is written not so much from the viewpoint of offering a synthetic rubber for practical use as from that of applying linear polyesters to the study of the relations between structure and properties of rubberlike substances in general. As has been pointed out in other articles, the linear polyesters are well suited to serve as models in such a study, since molecules of definitely known constitution and molecular-weight distribution can be synthesized by relatively simple methods. Furthermore, the chemical structure of the polyester chain molecules can be varied in a definite and controlled manner by the choice of suitable glycol and dibasic acid or hydroxy acid reactants. The structure of the chains in the case of the former, assuming equal molar proportions, may be represented by the general formula:

Research on Modified Rubbers. Part VI. The Oxidation of Rubber Solutions with Gaseous Oxygen in Presence of Catalysts

Abstract In a previous study of the oxidation of rubber, the oxidative action of peracetic acid, or mixtures behaving substantially as such, was examined (Bloomfield and Farmer, J. Soc. Chem Ind., 53, 121T(1934)). The results then obtained pointed to a course of reaction characterized by (a) additive attack at the unsaturated centers of the rubber molecules, resulting in the production of a high degree of hydroxylation, and (b) extensive molecular degradation with liberation of carbon dioxide (see also Mair and Todd, J. Chem. Soc., 1932, 386). In an extension of this work, attempts have been made to prepare peracetic acid by means other than the interaction of hydrogen peroxide with acetic acid or anhydride, and among other methods the autoxidation of acetaldehyde at low temperatures in the presence of cobalt acetate as catalyst (G P. 269,937; U.S.P. 1,179,121) was tried. Though peracetic acid was successfully obtained in this way in fair yield, an attempt to prepare it on a larger scale resulted in a violent explosion. In order to eliminate the danger arising from an accumulation of peracetic acid, oxygen was led into a chloroform solution of rubber containing a cobalt acetate catalyst together with acetaldehyde, with the hope that in this way peracetic acid might be formed in situ; at low temperatures (−20° to 0°) no reaction occurred, but on submitting such a solution to the action of oxygen at temperatures above 30° a very rapid reduction of viscosity set in, and the solution yielded a viscous gum containing a little oxygen. Now Stevens and his co-workers have recently shown that rubber solutions readily undergo oxidation by gaseous oxygen when certain catalysts (notably the heavy metal salts of organic acids) are present. It immediately became apparent that the oxidation phenomenon just described affords the basis for a greatly accelerated process of this type, the acceleration being due to the presence of acetaldehyde. It was thought desirable at this stage to investigate broadly the entire subject of oxidation of rubber solutions in the presence of catalysts of this nature, and a study has accordingly been made of the oxygen absorption of rubber solutions containing different catalysts, the oxygen intake being measured by the contraction occurring in a closed system containing oxygen, the latter being kept constantly circulating by means of a pump of the pattern designed by Finch (J. Chem. Soc., 1925, 2464). Since it was found that a considerable quantity of carbon dioxide was formed during oxidations of this type, the circulating gases were passed through a trap containing baryta water, and at any stage of the oxidation the amount of carbon dioxide formed could be ascertained by removing the contents of the trap, filtering off the precipitated barium carbonate, and determining the barium as sulfate.

STUDIES ON BACTERIAL LOCALIZATION

THE RESULTS OF GROSS AND MICROSCOPIC OBSERVATIONS AND SURVIVAL TESTS AFTER SUBCUTANEOUS INFECTION OF MICE WITH TYPE I PNEUMOCOCCI CAN BE SUMMARIZED AS FOLLOWS: Normal mice possessed no adequate means of protection against this organism. The bacteria disseminated freely through the tissue spaces in the presence of widespread inflammation, and were not ingested by significant numbers of host cells. Macrophages mobilized in the subcutis by intraperitoneal vaccinations with homologous killed organisms promptly ingested the living bacteria subsequently introduced. The cocci were sharply localized and destroyed in the presence of minimal amounts of exudation, edema and necrosis. Bacterial localization accompanied a similar hypoergic reaction after passive immunization. When a hyperergic response was induced by repeated local, in addition to intraperitoneal, vaccinations, prompt phagocytosis by macrophages, as after intraperitoneal vaccination alone, was again the outstanding means of disposal of the organisms. The heightened exudation, edema and local necrosis resembled a harmful rather than an important localizing reaction. Immunity was not dependent upon a hyperergic reaction. Prompt in vivo agglutination of living bacteria after passive immunization was an important early localizing phenomenon. After either active or passive immunization, phagocytosis was the only means observed by which the organisms were destroyed. Thus localization and destruction of the bacteria in immunized mice were dependent both on bacterial changes caused by specific antibody and on phagocytic activities of host cells. A viscous gum acacia medium caused a transient delay in bacterial dissemination, but the organisms ultimately became widely scattered in the tissues of the abdominal wall. The animals died earlier, with more extensive and destructive lesions than when the bacteria were introduced in a saline medium. In distinct contrast, the pneumococci were as a rule sharply localized and destroyed when injected in an acacia medium containing a small amount of immune serum. After local active immunization, sufficient to protect about half the animals subsequently infected by pneumococci in a saline medium, extensive and destructive lesions and death of the mice followed introduction of the organisms in acacia. It was suggested that the more viscous medium may have hindered diffusion of immune bodies from the tissues into the inoculum.