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At least 829 records · Page 46Linked to original sources
PubMed2001

GDNF protects against aluminum-induced apoptosis in rabbits by upregulating Bcl-2 and Bcl-XL and inhibiting mitochondrial Bax translocation.

Direct (intracisternal) injection of aluminum complexes into rabbit brain results in a number of similarities with the neuropathological and biochemical changes observed in Alzheimer's disease and provides the opportunity to assess early events in neurodegeneration. This mode of administration induces cytochrome c release from mitochondria, a decrease in Bcl-2 in both mitochondria and endoplasmic reticulum, Bax translocation into mitochondria, activation of caspase-3, and DNA fragmentation. Coadministration of glial cell neuronal-derived factor (GDNF) inhibits these Bcl-2 and Bax changes, upregulates Bcl-XL, and abolishes the caspase-3 activity. Furthermore, treatment with GDNF dramatically inhibits apoptosis, as assessed by the TUNEL technique for detecting DNA damage. Treatment with GDNF may represent a therapeutic strategy to reverse the neuronal death associated with Alzheimer's disease and may exert its effect on apoptosis-regulatory proteins.

Alzheimer Disease↗
PubMed2001

Evaluation of health aspects of kojic acid in food.

Kojic acid is a fungal metabolite commonly produced by many species of Aspergillus, Acetobacter, and Penicillium. The Aspergillus flavus group has traditionally been used in the production of a number of foods, including miso (soybean paste), shoyu (soy sauce), and sake. Kojic acid is widely used as a food additive for preventing enzymatic browning, and in cosmetic preparations as a skin-lightening or bleaching agent. Because kojic acid is often produced during the fermentation of historically used dietary staples, it has a long history of consumption. Various types of compounds, such as glucose, sucrose, acetate, ethanol, arabinose, and xylose, have been used as carbon sources for kojic acid production. Different Aspergillus species are known to produce variable amounts of kojic acid. The mechanism of action of kojic acid is well defined and it has been shown to act as a competitive and reversible inhibitor of animal and plant polyphenol oxidases, xanthine oxidase, and D- and some L-amino acid oxidases. The structure of kojic acid indicates a relatively simple route of metabolism much like dietary hexoses. Acute or subchronic toxicity resulting from an oral dose has not been reported, but convulsions may occur if kojic acid is injected. Results of mutagenicity studies are mixed, but in the in vivo mammalian dominant lethal assay, kojic acid was proven negative. Continuous administration of high doses of kojic acid in mice resulted in induction of thyroid adenomas in both sexes. Kojic acid reversibly affects thyroid function primarily by inhibiting iodine uptake, leading to decreases in T3 and T4 and increase in TSH. Increased TSH from pituitary gland in turn stimulates thyroid hyperplasia. Several lines of evidence indicate that the proliferative effects of kojic acid on thyroid are not related to a genotoxic pathway. The risk of functional inhibition of iodine uptake and its metabolism (organification) and thyroid tumor induction by kojic acid in humans appears to be extremely low. Based on the literature reviewed and discussed here, consumption of kojic acid at levels normally found in food does not present a concern for safety.

Animals↗
PubMed1993

Essential fatty acid deficiency in cultured human keratinocytes attenuates toxicity due to lipid peroxidation.

Human keratinocytes are commonly grown in culture with a serum-free medium. Under these conditions, keratinocytes become essential fatty acid deficient (EFAD), as determined by gas chromatographic analysis of cell phospholipid fatty acid composition. Exposure of EFAD keratinocytes for 2 hr to concentrations of t-butyl hydroperoxide (tBHP) up to 2 mM did not result in toxicity assessed by lactate dehydrogenase (LDH) release and only a small indication of lipid peroxidation assessed by the release of thiobarbituric acid-reactive substances (TBARS). Addition of 10 microM linoleic acid (LA) to serum-free medium alleviated the EFAD condition by increasing the phospholipid content of LA and its elongation and desaturation products, arachidonic acid and docosatetraenoic acid. Exposure of LA-supplemented keratinocytes to tBHP resulted in significant LDH (at 1 and 2 mM tBHP) and TBARS (tBHP concentration dependent) release. TBARS release was also significantly elevated in unexposed LA-supplemented keratinocytes (basal release). Co-supplementation with the antioxidant, alpha-tocopherol succinate (TS) prevented tBHP (1 mM)-induced LDH release in LA-supplemented cultures. TS supplementation also attenuated the effect of tBHP on TBARS release, but when compared to TS-supplemented EFAD cultures, LA supplementation still led to increased tBHP-induced TBARS release. Keratinocyte cultures are potentially useful as an alternative to animals in toxicology research and testing. It is important, however, that the cell model provide a response to toxic insult similar to that experienced in vivo. Our results suggest that fatty acid and antioxidant nutrition of cultured keratinocytes are important parameters in mediating the toxic effects of lipid peroxidation.

Cells, Cultured↗
PubMed1998

Volatile components formed from reaction of sugar and beta-alanine as a model system of cookie processing.

Volatile components formed from the reaction of monosaccharides or disaccharides with beta-alanine were investigated in a dry condition as a model system of cookie processing. Maltol is a common compound formed in the Maillard reaction, but it was very difficult to detect it in previous experiments using actual cookie materials. In this work, we investigated the principal compounds and maltol formation from the reaction of monosaccharides or disaccharides with beta-alanine at 150 degrees C for 10 min. Neither the reaction of monosaccharides nor the disaccharides with beta-alanine resulted in the formation of maltol. 2,3-Dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP) was detected as a principal product from the reaction of monosaccharides with beta-alanine. 5-Hydroxymethyl-2-furfural was also confirmed as being a major product in both reactions.

Acetylation↗
PubMed1998

Chemometric applications of thermally produced compounds as time-temperature integrators in aseptic processing of particulate foods.

The chemometric principle was used to derive a guideline for obtaining a simple "yes or no" answer about the sterility of food particulates heated at aseptic processing temperatures. A quadratic temperature pulse model was used to estimate bacterial destruction from the fractional yield of thermally produced chemical marker compounds (2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one, M-1, and 4-hydroxy-5-methyl-3(2H)-furanone, M-2) and the rate constants and the activation energies of the chemical and bacterial systems. The model yielded a conservative estimate of lethality at the center of meat-balls heated under different time-temperature conditions. A scheme for determining the minimum marker yield for a designated Fo-value is provided.

Food Analysis↗
PubMed2004

Enzymatic synthesis of structured lipids.

Structured lipids (SLs) are defined as lipids that are modified chemically or enzymatically in order to change their structure. This review deals with structured triacylglycerols (STGs) and structured phospholipids (SPLs). The most typical STGs are MLM-type STGs, having medium chain fatty acids (FAs) at the 1- and 3-positions and a long chain fatty acid at the 2- position. MLM-type STGs are synthesized by: 1) 1,3-position-specific lipase-catalyzed acyl exchange of TG with FA or with FA ethylester (FAEt); 2) 1,3-position-specific lipase-catalyzed acylation of glycerol with FA, giving symmetric 1,3-diacyl-sn-glycerol, followed by chemical acylation at the sn-2 position, and; 3) 1,3-position-specific lipase-catalyzed deacylation of TG, giving 2-monoacylglycerol, followed by reacylation at the 1- and 3-positions with FA or with (FAEt). Enzymatic preparation of SPLs requires: 1) acyl group modification, and 2) head group modification of phospholipids. Acyl group modification is performed using lipases or phospholipase A2-mediated transesterification or ester synthesis to introduce arbitrary fatty acid to phospholipids. Head group modification is carried out by phospholipase D-catalyzed transphosphatidylation. A wide range of compounds can be introduced into the polar head of phospholipids, making it possible to prepare various SPLs.

Arbutin↗
PubMed1994

Cytochemical study of the effect of aluminium on cultured brain microvascular endothelial cells.

The cytotoxic effect of aluminium was studied on cultured goat brain microvascular endothelial cells used as an in vitro model of the blood-brain barrier. Confluent monolayers of these cells were exposed for 4 days to aluminium maltol and, for control purposes, to maltol alone, and also to cadmium chloride as a known cytotoxic substance. The localization of plasmalemma-bound enzymatic activities of 5'-nucleotidase and Ca(2+)-ATPase and the distribution of sialic acid residues were studied at the ultrastructural level. It was observed that the reaction for 5'-nucleotidase activity was only insignificantly affected, indicating its resistance to the cytotoxic action of both substances used. On the contrary, the activity of Ca(2+)-ATPase was evidently suppressed, especially in the interendothelial clefts where junctional complexes are presumably to be formed. Aluminium also affects the density of sialic acid residues, as shown by their redistribution, leading to the appearance of relatively long segments of unlabelled apical cell surface. The data obtained suggest that observed changes in the localization of Ca(2+)-ATPase and sialic acid residues can lead ultimately to impairment of the formation and maintenance of intercellular junctions and to disturbances in the negatively charged domains of the endothelial cell surface. Whether these alterations, induced in vitro, contribute to in vivo disturbances of blood-brain barrier function requires further experimental study.

5'-Nucleotidase↗
PubMed1991

Comparative toxicity of fostriecin, hepsulfam and pyrazine diazohydroxide to human and murine hematopoietic progenitor cells in vitro.

The in vitro myelotoxic potentials of three investigational antitumor agents, Fostriecin, Hepsulfam and pyrazine diazohydroxide (PZDH), were evaluated utilizing clonogenic assays. Human and murine marrow cells were exposed to each drug for 1 hr prior to culture in microcapillary (human) or Petri dish (murine) assays. Fostriecin (0.22-220 microM), Hepsulfam (0.34-340 microM) and PZDH (0.68-680 microM) inhibited myeloid (CFU-gm), erythroid (BFU-e, CFU-e) and megakaryocytic (CFU-meg) colony formation in a concentration-dependent manner. CFU-e from both species were more sensitive to Fostriecin than the other progenitors and murine cells more sensitive overall to Fostriecin than their human counterparts. Murine CFU-e were also more sensitive to Hepsulfam than human CFU-e, with CFU-gm and BFU-e being similarly affected in both species. Human BFU-e were greatly inhibited by PZDH, whereas murine BFU-e were relatively resistant to its toxic effects. Fostriecin was the most toxic of the three antitumor agents, with PZDH the least toxic.

Alkenes↗
PubMed1994

Platelet labelling with indium-hydroxypyridinone and indium-hydroxypyranone complexes.

In order to identify new compounds which label platelets without affecting their function, three classes of metal chelating agents have been compared with oxine for their efficiency of indium-113m platelet labelling and for their short- and long-term effects on platelet function. The 3-hydroxypyridinones (both 2-ones and 4-ones) and 3-hydroxypyranones are bidentate chelators of trivalent metal ions that are neutrally charged in the metal-complexed form and hence gain access to cells readily. The hydroxypyranone ethylmaltol has been compared with the 3-hydroxypyridin-4-one CP94 and to its structurally related lipophilic analogue CP25 as well as with the 3-hydroxypyridin-2-one, CP02. The platelet labelling efficiencies with these ligands were between 75% and 95% of that obtained with oxine, following a 12-min incubation in saline. The optimal concentration for the hydroxypyridin-2-ones and hydroxypyridin-4-ones was approximately 10 microM compared with 100 microM for the hydroxypyranone ethylmaltol and 60 microM for oxine. Oxine and tropolone were found to produce significant inhibition of platelet aggregation to collagen in short-term experiments (10 min) or in longer term (18 and 42 h) ex vivo platelet cultures respectively. By contrast, ethylmaltol had no such inhibitory effects at either time interval. The relatively hydrophilic hydroxypyridin-4-one CP94 showed no inhibitory effects on collagen-induced aggregation in short-term studies, unlike the more lipid-soluble derivative CP25. These results suggest that ethylmaltol and related pyranones may have advantages over oxine and tropolone as indium platelet labelling agents where it is important not to damage platelets by the labelling process itself.

Blood Platelets↗
PubMed1992

Controlled mycelial growth for kojic acid production using Ca-alginate-immobilized fungal cells.

Conidia of Aspergillus oryzae were immobilized in Ca-alginate beads and then incubated in a nutrient medium to yield an immobilized biocatalyst producing kojic acid. The immobilized cell cultures produced kojic acid linearly during cultivation. Regardless of the size of the immobilized particles, there existed an optimal nitrogen concentration for the maximum production rate of kojic acid, at which smaller bead sizes resulted in a higher production rate. When the growth of mycelia were confined within the bead surface and segregated from each other by gel material, they produced kojic acid with maximal catalytic activity and exhibited the highest conversion yield of glucose. The extent of mycelial segregation was especially higher in cultures of smaller bead particles, and the depth of mycelial growth was 150 to 250 microns from the gel bead surface in all cultures of different nitrogen concentrations and bead sizes. Therefore, for the maximum expression of catalytic activities of immobilized mycelial cultures, it was found very critical to optimally control the mycelial distribution in gel beads by the culture conditions affecting mycelial growth.

Alginates↗
PubMed1984

Studies on the biochemical mechanism of the novel antitumor agent, CI-920.

Biochemical studies on a new antitumor antibiotic, CI-920, have been directed toward understanding its mode of action. The most striking effect brought on by CI-920 was a marked inhibition of macromolecular synthesis. L1210 leukemia cells exposed to 10 microM CI-920 exhibited a decreased rate of DNA, RNA, and protein synthesis within 45 min, and maximal inhibition occurred within 60 min. The reduction in nucleic acid synthesis was not due to precursor depletion, since ribonucleoside and deoxyribonucleoside triphosphate levels in cells exposed to 10 microM CI-920 for 2 h either remained unchanged relative to control cells or were elevated, suggesting a block more directly at the level of nucleotide incorporation. Nevertheless, CI-920 (50 microM) had no effect on DNA or RNA polymerase activity as assessed in permeabilized L1210 cells. However, if viable cells were exposed to 20 microM CI-920 for 1 h prior to permeabilization and then the polymerases assayed in the absence of drug, there was a 60% depression in enzyme activity. The inhibition of RNA polymerase appears to result from an effect on the enzyme rather than the template, since inhibition of RNA polymerase activity in cell-free systems from drug-treated cells could not be restored by addition of excess DNA template. DNA polymerase, however, was at least partially restored by addition of template and therefore was inconclusive in this respect. The data, then, suggest that CI-920 inhibits nucleic acid synthesis directly at the level of nucleotide incorporation, either by direct inhibition of DNA or RNA polymerase or by inactivation of an essential component of these enzyme systems. Since the drug in its parent form did not inhibit nucleic acid synthesis in cell-free systems the effects may possibly be mediated through conversion of this agent to another chemical form within viable cells.

Alkenes↗
PubMed1990

Aluminium-induced tangles in cultured rat neurones. Enhanced effect of aluminium by addition of maltol.

Neurofilamentous tangles have been induced in cultured neurones from rat brain hemispheres by application of both aluminium and maltol. Quantitative evaluation revealed a significantly higher percentage of tangle containing neurones when using the aluminium-maltol mixture than after application of aluminium alone. Tangles were found to be consistently stained with monoclonal antibodies to neurofilament proteins but failed to react with polyclonal antibodies against microtubule-associated proteins 1, 2 and tau.

Aluminum↗
PubMed1993

Lead transport and binding by human erythrocytes in vitro.

Transport and binding of Pb2+ by human erythrocytes were examined for cell Pb contents in the 1-10 microM range, using the 203Pb isotope. Pb2+ crosses the erythrocyte membrane by the anion exchanger, and can also leave erythrocytes by a vanadate-sensitive pathway, identified with the Ca2+ pump. However, Pb2+ exit is very much less than expected from earlier experiments with resealed erythrocyte ghosts [Simons TJB (1988) J Physiol (Lond) 405:105-113] and the distribution of Pb2+ across the erythrocyte membrane is close to equilibrium. The high ratio of erythrocyte to plasma Pb seen in vivo appears to be due to the presence of a labile Pb(2+)-binding component present in erythrocyte cytoplasm.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗