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31.
Urinary galactitol in galactosemic patients 总被引:2,自引:0,他引:2
32.
33.
A proteolytically modified form of the Escherichia coli single-stranded DNA-Binding protein (SSB) has been crystallized from 15% saturated sodium citrate. Crystals as large as 1.0 mm x 0.3 mm x 0.2 mm were obtained and these diffract beyond 3A resolution. X-ray photographic analysis demonstrated a rhombohedral unit cell of space group R3 with an equivalent triple centered hexagonal unit cell having dimensions of a = b = 62.9A and c = 264.3A. These crystals were judged to be adequate for a three dimensional structure determination. 相似文献
34.
M H Kim R Nakayama P Manos J E Tomlinson E Choi J D Ng D Holten 《Journal of lipid research》1989,30(5):663-671
Rats were fasted or fasted and refed simple purified diets so the effects of individual carbohydrates or fats could be studied. Freshly isolated hepatocytes from these animals were used to measure both apoE synthesis and mRNA levels so any changes in apoE synthesis that might occur without changes in its mRNA could be detected. Some of these experiments were done with both sexes. Both fasting and fasting and refeeding a 60% glucose fat-free diet significantly increased spoE synthesis. However, cyclic AMP is not likely to rapidly mediate the effect of fasting since dibutyryl cAMP slightly lowered (rather than increased) apoE synthesis and mRNA when injected into rats for 4.5 h. Dietary fat had no effect either in the absence of carbohydrate or when consumption of carbohydrate was constant in pair-fed rats. ApoE mRNA levels remained normal for 4 days in primary hepatocytes cultured in medium that had only amino acids as an energy source. Added hormones or fructose had no significant effect. Thus, only fasting and fasting and refeeding glucose were able to significantly change apoE synthesis or mRNA levels. Synthesis of apoE may be regulated to increase when apoE is secreted with very low density lipoprotein or when apoE in secreted high density lipoprotein is needed to acquire cholesteryl esters for the synthesis of bile salts and acids by liver. 相似文献
35.
Summary The condensation reactions of activated nucleotides, ImpN or 2-MeImpN, with the selfcomplementary ribo-octanucleotide GCGCGCGC or with the partially self-complementary heptanucleotide GCGCGCG were studied. The templatedirected reaction of 2-meImpC with the heptamer yields the 3–5 octamer as the main product. All other reactions yield 2–5-linked octamers and pyrophosphates as major products. Surprisingly, 2-MeImpG facilitates the reaction of 2-MeImpC with the heptamer.Procedures for the analysis by gel electrophoresis of the oligomeric products obtained in reactions of this kind are described. 相似文献
36.
C K Ng C J Handley B N Preston H C Robinson 《Archives of biochemistry and biophysics》1992,298(1):70-79
Hyaluronan was shown to have the same turnover time as aggrecan in explant cultures of adult bovine articular cartilage. Inclusion of fetal calf serum in the culture medium resulted in a similar decrease in the rate of catabolism of both hyaluronan and proteoglycan. Less than 9% of the hyaluronan lost from the explants in the course of the experiment was recovered from the culture medium as hyaluronan, suggesting that the catabolism of hyaluronan involves the uptake of this glycosaminoglycan by the chondrocytes. Analysis of the molecular size of the newly synthesized hyaluronan in these cultures showed that the hyaluronan was initially synthesized as large macromolecules that were gradually depolymerized with time within the extracellular matrix. The resulting size distribution of newly synthesized hyaluronan molecules after 12 days in culture was similar to that determined for the endogenous hyaluronan. The kinetics of depolymerization of the newly synthesized hyaluronan was consistent with a random fragmentation of the macromolecule. The rate constants for the depolymerization of hyaluronan indicate that oxygen-derived radicals may be involved in the fragmentation of this macromolecule. Inclusion of either cycloheximide or proteinase inhibitors in the medium of the explant cultures resulted in a marked decrease in the rate of loss of hyaluronan from the tissue and in the inhibition of the depolymerization of the newly synthesized macromolecule. This suggests that both the catabolism and the depolymerization of hyaluronan are cell mediated and depend on metabolically active cells. 相似文献
37.
Specificity of binding of beta-glucoside activators of ryegrass (1-->3)-beta-glucan synthase and the synthesis of some potential photoaffinity activators. 下载免费PDF全文
Structure-activity relationships among glycoside activators of ryegrass (Lolium multiflorum) (1-->3)-beta-glucan synthase were investigated using a number of natural and synthetic glycosides, including some carrying photoaffinity functions. There is an absolute requirement for a beta-D-glycosyl moiety in the activator, both S- and N-glucosides are active, and the position of the glucosidic linkage in beta-glucose disaccharides has a significant effect on the affinity of binding. However, the binding requirement does not extend beyond a single beta-D-glucosyl residue, and beta-D-oligoglucosides are less effective than disaccharides. The nature of the aglycon has a major influence on the binding affinity. Hydrophobic aglycons lower the concentration required for half-maximal stimulation of the enzyme obtained from an Eadie-Hofstee plot of kinetic data (Ka) for activation, but charge aglycons increase Ka. Relative to methyl-beta-D-glucoside and cellobiose (Ka 1.1 mM), the most potent compounds tested were N-[4-(benzoyl)benzoyl]-beta-D-glucosylamine and 2'-[4-azidosalicylamino]ethyl-1-thio-beta-D-glucoside with K(a)s of approximately 30 microM. The latter also was tested for its potential to specifically label the beta-glucoside-binding site on the synthase, but under the conditions used the binding was found to be nonspecific. 相似文献
38.
One of the most extreme freshwater habitats in Peninsular Malaysia is the peat swamp forest, with dark-coloured and highly acidic waters. Surprisingly, little is known about blackwater fishes in Peninsular Malaysia. Until 1968, only 26 fish species were known from blackwaters throughout Peninsular Malaysia, of which only one can be regarded as stenotopic. A recent intensive survey of part of the North Selangor peat swamp forest yielded 47 species, of which 14 are probably stenotopic taxa. These include four undescribed species and several new records for western Peninsular Malaysia. These discoveries are significant in that they include the family Chaudhuriidae which until 1985, was not reported from Sundaic Southeast Asia, and the rare genus Encheloclarias which had not been encountered for over 50 years. The rapid rate of destruction of the peat swamp forest owing to development, forestry and agricultural activities must be halted or slowed significantly to enable the proper zoological surveys and studies to be conducted. Conservation plans and environmental impact assessments based on inadequate sampling and knowledge of species present is acutely dangerous. There are no longer substantial undisturbed blackwater peat swamp forests left in most of Peninsular Malaysia. Conservation of the remaining blackwater biotopes is critically important if extinction of many species, here regarded as economically valuable renewable resources, is to be prevented. 相似文献
39.
Seven species of snakeheads (Channidae) are known from Peninsular Malaysia and Singapore, viz. Channa bankanensis, C. gachua, C. lucius, C. marulioides, C. melasoma, C. micropeltes and C. striata. Up-to-date distribution maps of each species are presented, including new records. Their systematics is reviewed and partially revised. The taxonomic status of C. marulioides and C. melanoptera is clarified. Specimens from Peninsular Malaysia identified as C. melanoptera sensu Weber & de Beaufort, 1922, proved to be the adult form of C. marulioides s.str. The real C. melanoptera appears to be restricted to Borneo and possibly Sumatra. The life history of a blackwater species C. bankanensis is also documented, with regards to the morphological and colour-pattern changes associated with growth. An updated key to the seven species based on morphometric measurements and meristic counts is presented. 相似文献
40.
Gordon Y. K. Ng †Brian F. O'Dowd ‡Mirelle Caron ‡Michael Dennis §Mark R. Brann † Susan R. George 《Journal of neurochemistry》1994,63(5):1589-1595
Abstract: We have expressed and biochemically characterized the human D2long (D2L ) dopamine receptor isoform using the baculovirus/Sf9 cell system. The expressed receptor bound ligands with a pharmacological profile similar to that reported for neuronal and cloned D2L receptors expressed in mammalian cell lines. Dopamine binding to D2L receptor was sensitive to guanine nucleotides, indicating receptor coupling to endogenous G proteins. A D2L receptor-specific antibody identified two major protein species at ∼44 kDa and at ∼93 kDa in immunoblots, suggesting the presence of D2L receptor monomers and dimers. Both species were purified by immunoprecipitation from digitonin-solubilized preparation of cells expressing D2L receptor prelabeled with 32 Pi or [3 H]-palmitate. These results constitute the first direct evidence for D2L receptor phosphorylation and palmitoylation. 相似文献