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Lack of carcinogenicity of tragacanth gum in B6C3F1 mice.

Tragacanth gum was administered at dietary levels of 0 (control), 1.25 and 5.0% to groups of 50 male and 50 female B6C3F1 mice for 96 wk after which all animals were maintained on a basal diet without tragacanth gum for a further 10 wk. Mean body weights of females in the 5.0% and 1.25% groups were lower than those of the controls after 11 and 16 wk, respectively. However, there were no treatment-related clinical signs or adverse effects on survival rate, urinalysis, haematology, blood biochemistry and organ weight. While detailed histopathology revealed the development of squamous cell hyperplasias, papillomas and one carcinoma in the forestomach, there was no significant treatment-related increase in the incidence of any preneoplastic or neoplastic lesion. Thus, under the experimental conditions used, tragacanth gum was not carcinogenic in B6C3F1 mice of either sex.

Animals

Oral toxicity study of tragacanth gum in B6C3F1 mice: development of squamous-cell hyperplasia in the forestomach and its reversibility.

Tragacanth gum was administered at dietary levels of 0 (control), 0.625, 1.25, 2.5, and 5.0% to groups of 10 male and 10 female B6C3F1 mice for 13 wk. There were no treatment-associated effects regarding clinical signs, body or organ weights, and urinalysis or hematology data. Significant dose-related, but slight, elevations of plasma gamma-glutamyl transpeptidase (GGT) level were observed in all treated animals except the 0.625% females. Single or small numbers of tiny nodules were observed on the luminal surface of the forestomach in 4 males of the 5.0% group, 2 males of the 2.5% group, and 1 male each from the 1.25 and 0.625% groups. Histopathologically, they were diagnosed as squamous-cell hyperplasia. To investigate the nature of these gross lesions, tragacanth gum was fed to groups of 30 male mice at the dietary level of 5.0% for periods of up to 48 wk; 20 males served as controls. There were no treatment-related increases of plasma GGT levels at wk 24 and 48. Although squamous-cell hyperplasias were seen in 2 out of 10 mice at wk 24, none of these proliferative lesions were apparent at wk 48, after either chronic exposure or 24 wk on basal diet. Furthermore, the levels of DNA synthesis in forestomach epithelium as measured by 5-bromo-2-deoxyuridine (BrdU) immunohistochemistry were comparable to control values at wk 24 and 48. Thus, the oral toxicity of tragacanth gum to B6C3F1 mice was concluded to be negligible.

Administration, Oral

Transmission electron microscopy of jejunum, ileum, and caecum tissues from rats fed with gums arabic, karaya and tragacanth.

Transmission electron microscopy has been used to study the ultrastructure of rat jejunum, ileum and caecum after dietary supplementation with 10% (w/w) gum arabic, 7% (w/w) gum karaya, 4% (w/w) gum tragacanth for 45 days. Scrutiny of 65 micrographs, undertaken independently by 2 specialists, revealed no abnormalities in any of the organelles in any of the micrographs. Twelve representative micrographs are reproduced here.

Animals

Evidence for the safety of gum tragacanth (Asiatic Astragalus spp.) and modern criteria for the evaluation of food additives.

Gum tragacanth (GT), affirmed as GRAS within the USA since 1961, was evaluated as 'ADI not specified' by JECFA in 1985. Within the EEC, GT has been permitted temporarily as a food additive (E413), without an ADI, since 1974; a decision regarding its permanent status must be reached before the end of 1988. This review collates the dietary, toxicological, immunological and chemical data available and presents the pre-requisite data concerning the 'Need' and low levels of utilization of GT.

Abnormalities, Drug-Induced

Biochemical effects of gum arabic, gum tragacanth, methylcellulose and carboxymethylcellulose-Na in rat heart and liver.

Repeated oral administration of commonly used suspending media, gum arabic, gum tragacanth, methylcellulose, and carboxymethylcellulose-Na to rats caused uncoupling of oxidative phosphorylation in liver and heart mitochondria and partial inhibition of mixed function oxidases of liver endoplasmic reticulum, as measured by 2-biphenylhydroxylation and 4-biphenylhydroxylation. There were considerable differences between the compounds with regard to potency and reversibility of these effects. Only methylcellulose at a concentration of 0.5% did not alter mitochondrial function and mixed function oxidases. It is recommended as suspending medium for the use in pharmacological and toxicological experiments.

Acacia

Use of gum tragacanth overlay, applied at room temperature, in the plaque assay of fish and other animal viruses.

Fish cells derived from rainbow trout gonad or Atlantic salmon are sometimes damaged by the relatively high temperature of agar overlay widely used for plaquing animal viruses. This heat-induced cell damage can be avoided by the use of gum tragacanth, which may be applied at room temperature. When the medium was buffered with tris(hydroxymethyl)aminomethane-hydrochloride and NaHCO3, the plaque assay could be performed without the use of a CO2 incubator. Using this method, a number of animal viruses were plaqued on a variety of cell monolayers at different temperatures under atmospheric ocnditions.

Agar

Interaction of preservatives with macromolecules: Part I--Natural hydrocolloids.

Antibacterial activity of methyl-p-hydroxybenzoate against Ps. aeruginosa was evaluated in the presence of varying concentrations of acacia, tragacanth, sodium alginate, guar gum and carrageenin. All these hydrocolloids reduced the antibacterial activity to varying degrees. Tragacanth and guar gum inhibited the activity to a greater extent than acacia, sodium alginate and carrageenin. Hydrocolloids reduce the antibacterial activity of preservatives in two ways. Interaction of the preservative with hydrophilic macromolecules and subsequent reduction in the availability of preservative appears to be the predominant mechanism by which tragacanth and guar gum reduce the activity of methyl-p-hydroxybenzoate. Acacia, sodium alginate and carrageenin apparently act by offering physical protection to microbial cells from the action of the preservative. It is also probable that these hydrocolloids provide more favourable media for microbial growth thereby increasing the preservative requirement for adequate preservation.

Colloids

Dietary fiber: in vitro methods that anticipate nutrition and metabolic activity in humans.

Gravimetric measurement of dietary fiber (DF) gives no indication of the biological function of any particular fiber. This study describes simple methods based on dialysis and fermentation that enable a hierarchy of fibers to be described for each of the major actions of fiber along the gastro-intestinal tract: nutrient absorption, sterol metabolism, cecal fermentation, and fecal bulking. These results were compared with previous metabolic studies with the same fiber isolates in humans. DF that modifies nutrient absorption can be identified by using dialysis studies, whereas identifying DF that modifies sterol metabolism, cecal fermentation, and fecal weight requires formulas that incorporate dialysis and fermentation results. Results from dialysis and fermentation predicted the action of wheat bran, pectin, guar, gum arabic, carboxymethylcellulose, gellan, tragacanth, xanthan, and karaya in humans and generated anomalous results for karaya and tragacanth. These methods could form the basis of techniques that would enable a screening of novel and processed fibers before studies in animals, including humans.

Bile Acids and Salts

Nitrogen conversion factors for the proteinaceous content of gums permitted as food additives.

Nitrogen conversion factors for gum arabic (Acacia senegal (L.) Willd.), gum tragacanth (Asiatic Astragalus spp.), gum karaya (Sterculia spp.), guar gum (Cyamopsis spp.), locust bean (carob) gum (Ceratonia spp.), tara gum (Caesalpinia spp.), and xanthan gum (Xanthomonas campestris) have been calculated from data for the amino acid compositions of their proteinaceous components. The factors derived differ from the arbitrary values (5.7 or 6.25) at present specified by international regulatory authorities for some emulsifiers, stabilizers and thickeners.

Dietary Proteins

Intratesticular injection as a method to assess the potential toxicity of various agents and to study mechanisms of normal spermatogenesis.

To better understand, to optimize, and to validate the technique of intratesticular (i.t.) injection, several parameters related to i.t. injection were examined. Volumes exceeding 50 microliters could be injected i.t.; however, testes frequently became excessively turgid and backflow of injected fluids occurred. Thus, a volume of 50 microliters or less was deemed optimal for injection. To determine the rate of distribution of substances throughout the testis, trypan blue was injected i.t. near the caudal pole of the testis, and the movement of dye was monitored. Within 2 min, the dye had spread approximately 1 cm from the site of injection, and in 5 min it had spread twice that distance. In 2 h, the dye had become distributed throughout the testis except at its extreme cranial pole. Seminiferous tubules did not take up dye, indicating that the spread of dye was via peritubular lymphatics. Seminiferous tubule histology appeared virtually unaffected by i.t. injection, even at regions adjacent to the site of injection, when a sterile 26-gauge or smaller bore needle was utilized. To determine disappearance from the testis, radiolabeled inulin was injected i.t. Half time for absorption was achieved at 1.75 h. Potential vehicles were explored in which compounds with a variety of physical properties could be injected. Gum tragacanth, normal saline, ethylene glycol, dimethyl sulfoxide (DMSO) mixed 1:1 with normal saline, sesame oil, and propylene glycol were found to be suitable injection vehicles, whereas ethanol, dissolved in normal saline in concentrations as low as 0.5% was found unsuitable. To assess vehicle efficiency, various vehicles were utilized with a known testicular toxin (taxol) and injected into one testis, and the histology was compared with the contralateral testis injected with vehicle alone. All vehicles, found suitable above, allowed dispersion of taxol to influence areas distant from the site of injection. Intratesticular injection assesses the potential of agents to directly affect the testis, and systemic metabolism is avoided. Their rapid spread throughout the lymphatics of the testes allows seminiferous tubules to be exposed to agents in innocuous vehicles more rapidly and in higher concentration than is often possible when using systemic injections.

Alkaloids

The effect of age on the adaptation of the brain to the anticonvulsant effect of phenobarbital in mice.

The anticonvulsant effect of phenobarbital was examined in young (6 month old) and old (24 month old) BDF1 female mice consisting of three groups each (one control and two chronically dosed phenobarbital groups), using the abolition of the tonic hindlimb extensor component of maximal electroshock seizure as the index. The minimal effective concentrations (MEC) of phenobarbital in plasma and brain in old control mice that were given a vehicle (tragacanth) for one week were significantly lower in comparison to the respective values in young adult control mice with the same treatment, confirming our previous findings. In young mice chronically treated with phenobarbital for one week (20 mg/kg daily for two days followed by daily dose of 50 mg/kg for 5 days), the MECs in both plasma and brain were significantly higher compared with respective control values. The 3 week treatment also produced an increase in MEc comparable to the one-week treatment. The same one-week treatment with phenobarbital in old mice similarly caused significantly higher plasma and brain MEC values but 3-week-treatment values were not significantly different from corresponding control values. It is concluded that the development of brain adaptation to phenobarbital is almost equal for young and old mice, so that the reduction in MEC with age indicates the need for lowered dosages for the aged, even when the age effect on brain adaptation developed to chronic dosing is taken into consideration.

Adaptation, Physiological

Composition of the gum from Combretum paniculatum and four other gums which are not permitted food additives.

Only three gum exudates are permitted for pharmaceutical and food use by international regulatory authorities, viz. gum tragacanth (Asiatic Astragalus spp.), gum karaya (Sterculia spp.) and gum arabic [Acacia senegal (L.) Willd.], but a wide range of other tree exudates is used for a variety of uses in their countries of origin. This paper presents analytical data for the gum exudates from Atalaya hemiglauca, Cassine aethiopica, Combretum paniculatum, Sclerocarya birrea, and Pseudocedrela kotschyi. These gums may have local technological applications, but are not recommended for addition to foodstuffs.

Amino Acids

Eximiradius proteiniborus gen. nov., sp. nov., the first cultivated representative of the "Candidatus Kapaibacteriia" (lineage OPB56) and a proposal of Eximiradiaceae fam. nov., Eximiradiales ord. nov., Eximiradiia class. nov. within the phylum Bacteroidota.

A novel strictly anaerobic moderately thermophilic bacterium, strain OB-3-phT, was isolated from a fouling under the flow of thermal well water (North Ossetia, Russian Federation). Gram-negative cells were nonspore-forming, straight motile rods, occasionally forming aggregates. The strain grew at 30-55 °C, pH range of 6.0-8.7, NaCl range 0-1.5%, with an optimum at 50 °C, pH 7.1 and 0.4% NaCl. It was a chemoorganoheterotroph, growing on proteinaceous substrates (albumin, gelatin, tryptone, casein, alpha-keratin) and carbohydrates (locust bean gum, guar gum, tragacanth, rhamnogalacturonan). Major products of glucose fermentation were acetate, propionate, hydrogen, and carbon dioxide. The genome size of strain OB-3-phT was 2.462 Mbp; DNA G + C content was 36%. Genome analysis enabled the identification of genes encoding a limited set of carbohydrate-active enzymes, as well as numerous extracellular metalloproteases and serine proteases. In addition, central metabolism and energy conservation pathways of strain OB-3-phT were reconstructed. Genes for respiration with oxygen and nitrite were identified, but due to the incompleteness of the menaquinone synthesis pathway, the strain obtains energy exclusively through fermentation. According to phylogenetic analyses based on 120 concatenated protein markers, strain OB-3-phT represents the first cultivated member of the deep phylogenetic lineage known as "Candidatus Kapaibacteriia" (lineage OPB56). Here we propose a novel genus and species Eximiradius proteiniborus with type strain OB-3-phT (=VKM B-3974T = UQM 42056T) within Eximiradiaceae fam. nov., Eximiradiales ord. nov. and Eximiradiia class. nov., respectively.

Bacteria

The effect of the polysaccharide composition and structure of dietary fibers on cecal fermentation and fecal excretion.

The fermentation of dietary fibers gives a clue to their mode of action. Wheat bran and gum tragacanth increase stool weight but have no effect on serum cholesterol or on hydrogen excretion. Gum arabic and pectin in the form of raw carrot have no effect on stool weight but decrease serum cholesterol and are associated with an increase in breath-hydrogen excretion. Other fiber sources like gum karaya have no effect on stool weight, serum cholesterol, or breath hydrogen. There are no correlations between the chemical composition and structure of the fibers studied and their physiological effects.

Breath Tests

Fermentation of mucin and plant polysaccharides by strains of Bacteroides from the human colon.

Ten Bacteroides species found in the human colon were surveyed for their ability to ferment mucins and plant polysaccharides ("dietary fiber"). A number of strains fermented mucopolysaccharides (heparin, hyaluronate, and chondroitin sulfate) and ovomucoid. Only 3 of the 188 strains tested fermented beef submaxillary mucin, and none fermented porcine gastric mucin. Many of the Bacteroides strains tested were also able to ferment a variety of plant polysaccharides, including amylose, dextran, pectin, gum tragacanth, gum guar, larch arabinogalactan, alginate, and laminarin. Some plant polysaccharides such as gum arabic, gum karaya, gum ghatti and fucoidan, were not utilized by any of the strains tested. The ability to utilize mucins and plant polysaccharides varied considerably among the Bacteroides species tested.

Bacteroides