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971.
Gas chromatographic assay of total and O-acetyl groups in bacterial lipopolysaccharides 总被引:2,自引:0,他引:2
An improved gas chromatographic method for the determination of total, i.e., amide- and ester-linked, acetyl groups in hydrolysates of bacterial lipopolysaccharides has been developed. After hydrolysis with 0.2 n HCl overnight at 100°C and adjustment of the hydrolysate to pH 3–4, 2 μl of the samples contalning 0–6 μg of acetic and 1–2 μg of propionic acid are directly injected into a gas chromatograph fitted with a 1.5-m glass column packed with Porapak QS. O-Acetyl groups can selectively be determined after hydrolysis with 0.05 n NaOH for 3–4 hr at room temperature and adjustment of the sample to pH 3–4. N-Acetyl groups can be calculated as the difference between total and O-acetyl. The above-mentioned phase allows quantitation of short-chain volatile fatty acids (S-C VFAs) up to n-valeric acid in a range of 0–6.0 μmol using an appropriate internal standard. 相似文献
972.
An immunoaffinity chromatography procedure for the isolation of bovine glial fibrillary acidic (GFA) protein is described. Degraded GFA protein isolated by hydroxyapatite chromatography from human spinal cord was used to prepare the antiserum. The immunoglogulin G fraction of the antiserum was covalently linked to CNBr-activated Sepharose, and columns of the immuno-affinity gel were used to adsorb bovine GFA protein from brain extracts. Elution was accomplished with a solution of 1 m acetic acid, 5 m urea, 0.8 m sodium chloride, pH 2.5. The yield of about 0.5 mg of highly purified protein/g of cerebral white matter could be increased to 1.5 mg/g of tissue by lowering the ionic strength of the extracting buffer from 50 mm to 1 mm sodium phosphate. Isolation in the presence of EDTA prevented the formation of an oxidation product migrating as a dimer of the monomeric species on SDS-polyacrylamide gel electrophoresis. 相似文献
973.
Juan A. Oliver Robert R. Sciacca Gilbert Le Cren Paul J. Cannon 《Prostaglandins & other lipid mediators》1982,24(5):641-656
To determine whether the renal vascular effect of arginine vasopressin (AVP) is modulated by renal prostaglandin E2 (PGE2) were determined during the infusion of AVP in dogs during control conditions and after the administration of the inhibitor of prostaglandin synthesis, indomethacin. During control conditions, intrarenal administration for 10 min of a dose of AVP calculated to increase arterial renal plasma AVP concentration by 75 pg/ml produced a slight renal vasodilation (p<0.01) and an increase in renal venous plasma concentration of PGE2. Renal venous PGE2 concentration during control and AVP infusion averaged 33 ± 7 and 52 ± 12 pg/ml (p<0.05), respectively. After administration of indomethacin, the same dose of AVP induced renal vasoconstriction (p<0.05) and failed to enhance renal venous PGE2 concentration (9 ± 1 to 8 ± 1 pg/ml). Intrarenal administration of 20 ng/kg. min of AVP for 10 min induced a marked renal vasoconstriction (p<0.01) and increased renal venous plasma PGE2. Renal venous PGE2 during control and AVP infusion averaged 31 ± 10 and 121 ± 31 pg/ml (p<0.01), respectively. Administration of the same dose of AVP following indomethacin produced a significantly greater and longer lasting renal vasoconstriction (p<0.01) and failed to increase renal venous plasma PGE2 (10 ± 1 to 9 ± 1 pg/ml). These results indicate that a concentration of AVP comparable to that observed in several pathophysiological conditions induces a slight renal vasodilation which is mediated by renal prostaglandins. The results also indicate that higher doses of AVP induce renal vasoconstriction and that prostaglandin synthesis induced by AVP attenautes the renal vasoconstriction produced by this peptide. 相似文献
974.
Simone Pouyet 《Geobios》1978,11(5):611-621
The bryozoa described by de Lamarck in 1816 are not well known. Four types of the Cellepora group have been found in the zoological collections of Museum d'Histoire naturelle in Paris: Celleporaria oculata, C. cristata, C. oliva and C. endivia. C. oculata is the type-species of the genus CelleporariaLamouroux, 1821. This revision confirms the synonymy of some species described subsequently. 相似文献
975.
A new species,Jacquinia pauciflora, is described from subtropical moist forest on karst hills (mogotes) in northwestern Puerto Rico.Jacquinia pauciflora is similar toJ. stenophylla Urban, from which it differs in several floral and leaf characters, but is possibly most closely related toJ. umbellata A. DC. A key to the species ofJacquinia occurring in Puerto Rico is provided. 相似文献
976.
GAUTHIER DOBIGNY MICHEL BAYLAC CHRISTIANE DENYS 《Biological journal of the Linnean Society. Linnean Society of London》2002,77(3):319-327
The lack of diagnostic traits in sibling species means that great quantities of biogeographical and ecological data held in museum collections cannot be utilized effectively, leading to underestimates of biodiversity. In this study we applied neural networks (NN) and canonical variates analyses (CVA) to landmark measurements on the skulls of the West African species Taterillus arenarius , T. petteri , T. gracilis and T. pygargus in an attempt to discriminate species previously identified unambiguously from their karyotypes. Among suggested differences, the relationship between inflation of the tympanic bullae and lower population density is discussed. Cross-validated classification rates did not exceed 73%. Two hypotheses are proposed to explain such high phenotypic similarity: morphological plasticity limited by environmental constraints and the possibility that speciation has been too recent to allow significant morphological divergence. © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 319−327. 相似文献
977.
978.
秦岭及陕北黄土区辽东栎林群落物种多样性特征 总被引:17,自引:0,他引:17
应用5种物种多样性测度指标及4种物种—多度分布模型对秦岭和黄土区辽东栎林种子植物物种多样性及木本植物种—多度分布进行了对比研究,结果表明:秦岭辽东栎林无论是群落物种多样性还是各层次的物种多样性均高于黄土区辽东栎林。秦岭辽东栎林木本植物种—多度分布符合对数正态分布而黄土区辽东栎林则符合对数级数分布,分布区气候差异是造成两类辽东栎林物种多样性差异的主要原因。物种—多度分布分析与物种多样性分析结果是一致的。 相似文献
979.
Locris rubens (Erichson) (Cercopidae: Homoptera) and Poophilus costalis (Walker) (Aphrophoridae: Homoptera) are endemic pests of sorghum (Sorghum bicolor (L.) Moench) in Nigeria and some other countries in West and Central Africa. Other hosts are maize, pearl millet, rice, sugarcane, and grasses. On sorghum, L. rubens lays eggs in the epidermis of the leaf sheath. There are five nymphal instars and development from egg to adult takes about 33 days. Both species of spittle bugs feed on all growth stages and all parts of sorghum, including the panicle. Feeding symptoms include yellow leaf blotching. Severe infestations often kill young leaves and plants. Under artificial infestation in cages, the severity of damage and associated symptoms as well as grain yield loss increased with an increase in the population density of spittle bugs. Infestation by 15 pairs of adult L. rubens 相似文献
980.
A bivalve fauna of Early Ordovician (late Arenig) age is described from the Hsiangyang Formation of the eastern part of West Yunnan, China. The fauna contains elements in common with Early Ordovician faunas of southern Gondwanan areas such as the Montagne Noire and Morocco and with those of Avalonia, together with several previously undescribed taxa. The following taxa are new: Biseriodonta simplex gen. et sp. nov.; Glyptarca sinensis sp. nov.; Trigonoglyptarca magna gen. et sp. nov.; Erhaiconcha xiangyangensis gen. et sp. nov.; Fasciculodonta impressa gen. et sp. nov.; Yunnanoredonia laevis gen. et sp. nov.; Daliella gen. nov.; Goniophorina ( Goniophorina ) contracta sp. nov.; Haidongoconcha radialis gen. et sp. nov.; Eopterinea aequiconcha gen. et sp. nov. The bivalve fauna includes the most diverse glyptarcid fauna and the earliest nuculanid and paracyclid known hitherto. Eastern West Yunnan belonged to the Indochina terrane and it is concluded that the bivalve fauna represents a high-latitude assemblage and that the Indochina terrane should be considered a component part of the Peri-Gondwanan continent in the Ordovician; its bivalve faunas contrast with those of neighbouring terranes which have affinities with those of lower latitudes. 相似文献