透明质酸改性的聚乳酸支架

背景：聚乳酸材料不具备细胞外基质材料的良好细胞亲和性能,采用化学方法将透明质酸交联制得的水凝胶具有良好的生物相容性。 目的：以透明质酸对新型多孔隙率聚乳酸支架的进行改性,观察改性后支架的细胞相容性的改变。 方法：采用盐析法制备出高孔隙率聚乳酸支架,采用低浓度NaOH进行表面轻度水解后,利用EDC和透明质酸进行支架的改性。 结果与结论：透明质酸改性聚乳酸支架在扫描电镜下显示为多微孔的三维立体结构,孔壁及界面平滑,孔隙之间可见更细小微孔相连。改性聚乳酸支架水滴渗入较快,改性后多孔支架的保水能力与吸水能力得到明显的改善;透明质酸改性聚乳酸支架上细胞黏附及增殖优于未改性聚乳酸支架。透明质酸改性聚乳酸组软骨细胞生长密度及基质分泌更加旺盛。表明透明质酸改性聚乳酸多孔支架仍保持多孔的三维结构,其水亲和力、吸水能力、保水能力和细胞相容性均得到明显改善。 关键词：透明质酸;聚乳酸;多孔支架;表面改性;水亲和力;吸水能力 doi:10.3969/j.issn.1673-8225.2012.03.023     

Intestinal folic acid absorption and the acid microclimate

The effects of various substances and circumstances on folic acid absorption and surface pH were investigated in vitro in rat proximal jejunum. Prior consumption of alcohol adlibitum, phenytoin and in vitro methotrexate had no effect on folate absorption. In contrast, ethanol in vitro, low sodium ion containing buffers in vitro and oral methotrexate given prior to experiment reduced absorption. Folate absorption did not correlate with water movement since methotrexate decreased folate but enhanced fluid absorption, ruling out direct coupling. Surface pH was elevated by the low sodium ion containing buffers, ethanol in vitro and oral methotrexate, correlating inversely with folate absorption. The parallelisms between absorption and changes in surface pH support the microclimate hypothesis of folic acid absorption where the rate of transport is largely determined by the surface pH of the proximal jejunum.Part of this work was presented at the Biochemical Society, Cambridge Meeting, 1977. Biochem Soc Trans 6:297–299 (1978)     

Pro-oxidant actions of alpha-lipoic acid and dihydrolipoic acid

There is strong accumulating evidence that a alpha-lipoic acid (LA) supplement is good insurance, and would markedly improve human health. LA is readily absorbed from the diet, transported to cells and reduced to dihydrolipoic acid (DHLA). Of the two compounds, DHLA evidently has greater antioxidant activity. Much research has focused on the antioxidant properties of these compounds. Aside from its antioxidant role, in vitro and in vivo studies suggest that LA and its reduced form DHLA also act as a pro-oxidant properties. Limited number of studies concerning the pro-oxidant potential of LA and DHLA were performed only in recent years. The ability of LA and/or DHLA to function as either anti- or pro-oxidants, at least in part, is determined by the type of oxidant stress and the physiological circumstances. These pro-oxidant actions suggest that LA and DHLA act by multiple mechanisms, many of which are only now being explored. LA has been reported to have a number of potentially beneficial effects in both prevention and treatment of oxygen-related diseases. Selection of appropriate pharmacological doses of LA for use in oxygen-related diseases is critical. On the other hand, much of the discussion in clinical studies has been devoted to the pro-oxidant role of LA. This aspect remains to be elucidated. In further studies, careful evaluation will be necessary for the decision in the biological system whether LA administration is beneficial or harmful.     

Microstructure of styrene-methacrylic acid and styrene-acrylic acid copolymers, 5 UV absorption study of styrene-methacrylic acid and styreneacrylic acid copolymers

UV absorption spectra of styrene-methacrylic acid and styrene-acrylic acid copolymers prepared in benzene solution and in emulsion were investigated. They were compared to UV spectra of derived copolymers prepared by methylation of the carboxyl groups of the parent copolymers. In the spectra of the methylated copolymers only a hypochromic effect on all peaks was observed, whereas in the spectra of the parent acid copolymers hypochromic as well as hyperchromic effects were found. They depend on the kind of acid, its content in the copolymer and on the type of the copolymer. These differences may be explained on the basis of hydrogen bonds formed between the π-electrons of phenyl rings and carboxyl groups. It seems that the most sensitive peak to these hydrogen bonds is that at 259 nm, while the peak at 269 nm is sensitive to electronic interactions between adjacent monomeric units.     

Bioconversions of ferulic acid, an hydroxycinnamic acid

Ferulic acid is the most abundant hydroxycinnamic acid in the plant world and is ester linked to arabinose, in various plant polysaccharides such as arabinoxylans and pectins. It is a precursor to vanillin, one of the most important aromatic flavor compound used in foods, beverages, pharmaceuticals, and perfumes. This article presents an overview of the various biocatalytic routes, focusing on the relevant biotransformations of ferulic acid using plant sources, microorganisms, and enzymes.     

Amino acid catabolic pathways of lactic acid bacteria

Lactic acid bacteria (LAB) constitute a diverse group of Gram positive obligately fermentative microorganisms which include both beneficial and pathogenic strains. LAB generally have complex nutritional requirements and therefore they are usually associated with nutrient-rich environments such as animal bodies, plants and foodstuffs. Amino acids represent an important resource for LAB and their utilization serves a number of physiological roles such as intracellular pH control, generation of metabolic energy or redox power, and resistance to stress. As a consequence, the regulation of amino acid catabolism involves a wide set of both general and specific regulators and shows significant differences among LAB. Moreover, due to their fermentative metabolism, LAB amino acid catabolic pathways in some cases differ significantly from those described in best studied prokaryotic model organisms such as Escherichia coli or Bacillus subtilis. Thus, LAB amino acid catabolism constitutes an interesting case for the study of metabolic pathways. Furthermore, LAB are involved in the production of a great variety of fermented products so that the products of amino acid catabolism are also relevant for the safety and the quality of fermented products.     

Hyaluronic acid

Hyaluronic acid was the only glycosaminoglycan found in detectable amounts in the pulmonary secretions of patients with cystic fibrosis. The compound gave a hexuronate/hexosamines molar ratio of approximately 1. Glucosamine represented over 98% of the total hexosamines, the remainder being galactosamine. No hexoses or sulfate could be detected. It moved as a single spot with the mobility of standard hyaluronic acid on cellulose acetate electrophoresis and this spot disappeared after digestion with testicular hyaluronidase. It was associated with trace amounts of protein, the major amino acids of which are aspartic acid, glutamic acid, glycine, and alanine.     

Syntheses and characterization of random copolymers of aspartic acid with lactic acid and glycolic acid

Random copolymerization of aspartic acid with lactic acid and with glycolic acid was carried out using o-phosphoric acid as catalyst.     

An amino acid transporter involved in gastric acid secretion

Gastric acid secretion is regulated by a variety of stimuli, in particular histamine and acetyl choline. In addition, dietary factors such as the acute intake of a protein-rich diet and the subsequent increase in serum amino acids can stimulate gastric acid secretion only through partially characterized pathways. Recently, we described in mouse stomach parietal cells the expression of the system L heteromeric amino acid transporter comprised of the LAT2-4F2hc dimer. Here we address the potential role of the system L amino acid transporter in gastric acid secretion by parietal cells in freshly isolated rat gastric glands. RT-PCR, western blotting and immunohistochemistry confirmed the expression of 4F2-LAT2 amino acid transporters in rat parietal cells. In addition, mRNA was detected for the B⁰AT1, ASCT2, and ATB(0+) amino acid transporters. Intracellular pH measurements in parietal cells showed histamine-induced and omeprazole-sensitive H⁺-extrusion which was enhanced by about 50% in the presence of glutamine or cysteine (1 mM), two substrates of system L amino acid transporters. BCH, a non-metabolizable substrate and a competitive inhibitor of system L amino acid transport, abolished the stimulation of acid secretion by glutamine or cysteine suggesting that this stimulation required the uptake of amino acids by system L. In the absence of histamine glutamine also stimulated H⁺-extrusion, whereas glutamate did not. Also, phenylalanine was effective in stimulating H⁺/K⁺-ATPase activity. Glutamine did not increase intracellular Ca²⁺ levels indicating that it did not act via the recently described amino acid modulated Ca²⁺-sensing receptor. These data suggest a novel role for heterodimeric amino acid transporters and may elucidate a pathway by which protein-rich diets stimulate gastric acid secretion.P. Kirchhoff and M.H. Dave contributed equally to this study and therefore share first authorship     

Microstructure of styrene-methacrylic acid and styrene-acrylic acid copolymers, 3. UV absorption study of methylated styrene-methacrylic acid and styrene-acrylic acid copolymers

The microstructure of styrene-methacrylic acid and styrene-acrylic acid copolymers prepared in emulsion was studied by UV absorption measurements of their methylated derivatives. For comparative purpose random and graft-block copolymers were also studied. Hypochromic effects at 259, 262, 264,5 and 269 nm are observed for both random and emulsion copolymers. The dependence of hypochromism at 269 nm on the content of methylated acid units suggests a similar microstructure of random and emulsion copolymers containing up to about 30 mol-% of acid and differences in the microstructure of emulsion and random copolymers containing greater amounts of acid, especially in case of styrene-acrylic acid copolymers. Moreover, it is found that UV absorption measurements may be used as a method of estimating the sequence length of styrene units in the copolymers.     

Improved method for simultaneous determination of ascorbic acid and dehydroascorbic acid, isoascorbic acid and dehydroisoascorbic acid in food and biological samples.

The total vitamin C amount in different food and plasma samples was determined by a dual detection system, after HPLC separation, with direct detection of ascorbic acid and indirect fluorimetric detection of dehydroascorbic acid after a post-column O-phenyldiamine derivatisation. The two active forms of vitamin C and their D-isomers were separated within 10 min. The repeatability was determined by measurement of several fruits and vegetables and ranged from 0.3 to 1.9% (relative standard deviation) for vitamin C. The reproducibility, based on double determinations, ranged from 1.9 to 3.6% for vitamin C, depending on the matrix. The reproducibility, based on several determinations of reference materials, ranged from 2.4 to 3.7% for ascorbic acid and from 4.3 to 5.8% for dehydroascorbic acid, again depending on the matrix.     

Effect of ascorbic acid on the serum folic acid estimation

Ascorbic acid added to the basal medium increased the growth response of Lactobacillus casei in folic acid standards. The effect in the serum extracts was not marked, resulting in lowered serum folic acid estimations. However, results obtained on prolonged incubation were similar whether ascorbic acid was added or not. The presence or absence of ascorbic acid and variation of the incubation period may account for differences in reported normal ranges of serum folic acid levels.     

Nucleic acid vaccines

There are no adequate vaccines against some of the new or reemerged infectious scourges such as HIV and TB. They may require strong and enduring cell-mediated immunity to be elicited. This is quite a task, as the only known basis of protection by current commercial vaccines is antibody. As DNA or RNA vaccines may induce both cell-mediated and humoral immunity, great interest has been shown in them. However, doubt remains whether their efficacy will suffice for their clinical realization. We look at the various tactics to increase the potency of nucleic acid vaccines and divided them broadly under those affecting delivery and those affecting immune induction. For delivery, we have considered ways of improving uptake and the use of bacterial, replicon or viral vectors. For immune induction, we considered aspects of immunostimulatory CpG motifs, coinjection of cytokines or costimulators and alterations of the antigen, its cellular localization and its anatomical localization including the use of ligand-targeting to lymphoid tissue. We also thought that mucosal application of DNA deserved a separate section. In this review, we have taken the liberty to discuss these enhancement methods, whenever possible, in the context of the underlying mechanisms that might argue for or against these strategies.     

Retinoic acid embryopathy

Retinoic acid, an analogue of vitamin A, is known to be teratogenic in laboratory animals and has recently been implicated in a few clinical case reports. To study the human teratogenicity of this agent, we investigated 154 human pregnancies with fetal exposure to isotretinoin, a retinoid prescribed for severe recalcitrant cystic acne. The outcomes were 95 elective abortions, 26 infants without major malformations, 12 spontaneous abortions, and 21 malformed infants. A subset of 36 of the 154 pregnancies was observed prospectively. The outcomes in this cohort were 8 spontaneous abortions, 23 normal infants, and 5 malformed infants. Exposure to isotretinoin was associated with an unusually high relative risk for a group of selected major malformations (relative risk = 25.6; 95 per cent confidence interval, 11.4 to 57.5). Among the 21 malformed infants we found a characteristic pattern of malformation involving craniofacial, cardiac, thymic, and central nervous system structures. The malformations included microtia/anotia (15 infants), micrognathia (6), cleft palate (3), conotruncal heart defects and aortic-arch abnormalities (8), thymic defects (7), retinal or optic-nerve abnormalities (4), and central nervous system malformations (18). The pattern of malformation closely resembled that produced in animal studies of retinoid teratogenesis. It is possible that a major mechanism of isotretinoin teratogenesis is a deleterious effect on cephalic neural-crest cell activity that results in the observed craniofacial, cardiac, and thymic malformations.