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31.
New Procedure for Extraction of Ammonium from Natural Waters for 15N Isotopic Ratio Determinations 下载免费PDF全文
A new method for extracting ammonium from natural waters for 15N isotopic ratio determination is described. The method employs the conversion of the ammonium nitrogen into indophenol, which is then concentrated onto an octadecylsilane column. The method shows accuracy and precision comparable to those of other methods described in the literature. Some results from field experiments on the Swedish west coast are presented. 相似文献
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33.
Fred Hanley 《Journal of experimental marine biology and ecology》1984,83(2):159-177
Quantitative data on the ways in which the different phases of the stoplight parrotfish (Sparisomaviride Bonnaterre) distribute their time among various activities in different habitats are presented. Individuals spent from 84–97% of their diurnal time swimming, feeding, and hovering. Additionally, large adults spent a significant amount of time sheltering among crevices. Phase-related differences in these activities are statistically significant, as are differences in duration and rates of change of the activities. Large individuals spent more time swimming, while small individuals spent more time hovering. In addition, large individuals performed longer bouts of activity and switched activities less frequently than small individuals. Adult males and females spent approximately equal proportions of time in each of the activity states. Stochastic analyses of behavioural sequences show second order Markov chain dependencies, suggesting that preceding activity states affect subsequent behaviour. Possible relationships between behavioural sequencing and the species foraging strategy are discussed, and it is suggested that the sequence of behavioural activities can provide an estimation of the distribution of food resources in the environment. 相似文献
34.
Dolichol and Dolichyl Phosphate Levels in Brain Tissue from English Setters with Ceroid Lipofuscinosis 总被引:5,自引:1,他引:4
R. Kennedy Keller Donald Armstrong† Fred C. Crum Nils Koppang† 《Journal of neurochemistry》1984,42(4):1040-1047
Human ceroid lipofuscinosis (CL) is an inherited disease marked by cerebromacular degeneration and early death. We have utilized the canine model to investigate the possible role of dolichol and dolichyl phosphate in the developmental pathology of CL. We found that while brain levels of dolichol increase with age in both affected and unaffected dogs, the amount in the diseased animal was similar to that in controls. Brain levels of dolichyl phosphate ranged from 20 to 35 micrograms/g in control dogs at all ages examined, but increased substantially during development in the affected dogs, a value of 113 +/- 24 micrograms/g (mean +/- SD) being obtained in the end-stage animals. In addition to the results obtained in the canine model, dolichyl phosphate levels in human brain tissues from a 5-year-old with late infantile CL and from a 19-year-old with juvenile CL were found to be 153 and 382 micrograms/g, respectively, compared with a control that assayed 26 micrograms/g. The preliminary findings with human tissues provide further evidence for an association of elevated brain dolichyl phosphate levels with CL. Whether the increase is primary or secondary remains to be determined. 相似文献
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36.
Wim R. Klein Peter A. Steerenberg Fred Poelma Elly v. d. Wiel Victor P. M. G. Rutten Wim Misdorp Wim H. de Jong E. Joost Ruitenberg 《Cancer immunology, immunotherapy : CII》1986,22(2):87-94
Summary Lymphocyte stimulation with Con A and specific immune reactivity to BCG (antibody formation to BCG and DTH reaction to PPD) were determined in BCG-treated, surgically treated and untreated cows with ocular squamous cell carcinoma. In tumor-bearing cows the Con A-induced proliferation of lymphocytes was reduced when compared to healthy controls. This suppression consisted of a reduced blastogenic response to Con A of lymphocytes from tumor-bearing cows, and the presence of a factor in the sera of these animals, as these sera suppressed the blastogenic response of lymphocytes from healthy cows. BCG had only a minor influence on the suppressive activity. Antibodies to BCG were demonstrated in 50% of the BCG-treated animals. The formation of antibodies was not influenced by intradermal injection of PPD of Mycobacterium bovis. Absorption of a BCG antibody containing serum with BOSCC tumor extracts did not reveal the existence of cross reacting antigens between BCG and BOSCC. Pretherapeutic and posttherapeutic Con A reactivity could not be correlated with clinical response. Of the 30 BCG treated cows 29 developed a positive DTH reaction to PPD. Correlation between clinical response and immune reactivity was seen only with regard to the DTH reaction to PPD: this reaction remained positive for a longer period after treatment in animals with a favorable clinical outcome than in nonresponding animals.Animals were maintained under the guidelines laid down by the Faculty of Veterinary Medicine, State University, Utrecht, The NetherlandsGrant recipient of the Koningin Wilhelmina Fonds (Netherlands Cancer Foundation)
Abbreviations used: BCG, Bacillus Calmette-Guerin; BOSCC, bovine ocular squamous cell carcinoma PBL peripheral blood leukocytes; PPD, purified protein derivative of Mycobacteria; DTH, delayed type hypersensitivity Con A, concanavalin A; PHA, phytohemagglutinin; PWM, pokeweed mitogen 相似文献
37.
Abstract The first step of aerobactin biosynthesis, oxidation of an aliphatic primary amino group to an N -hydroxy-amino compound seems to be involved in the biosynthesis of most of the hydroxamatetype siderophores which are widely distributed among bacteria and fungi. Therefore, the first step of aerobactin biosynthesis, oxidation of lysine to N 6 -hydroxylysine was studied as a model reaction using a strain of Escherichia coli that contains the first gene aerA of aerobactin synthesis on a multi-copy plasmid and which is lacking the gene for the subsequent step in the pathway. In addition, culture conditions are described which lead to the secretion of N 6 -hydroxylysine into the medium in amounts that can easily be quantitatively determined by a simple, reliable chemical assay. This assay can be used for screening inhibitors of the oxidation of α-amino groups, which should interfere with the biosynthesis of siderophore hydroxamates and thus should create bacteriostatic conditions. 相似文献
38.
Thomas T. Stevenson Richard H. Furneaux David Pang Fred Shafizadeh Lyle H. Jensen Ronald E. Stenkamp 《Carbohydrate research》1983,112(2):179-187
A single-crystal, X-ray diffraction study was performed on a nonalkenic, cyclic trimer (C18H18O9, 4) of levoglucosenone, in order to confirm its chemical structure. Crystals of 4 are orthorhombic, with unit-cell parameters of a = 792.20, b = 1874.35, c = 2383.02 pm, space group P212121, and z = 8. The structure was solved by direct methods, and refined by least-squares to R = 0.032, based on 2990 unique reflections. Each asymmetrical unit contains two symmetry-independent molecules of 4 and one of acetone. The previously assigned chemical structure and stereochemistry of 4 were found to be correct. 相似文献
39.
Ganglioside-Induced Neuritogenesis: Verification That Gangliosides Are the Active Agents, and Comparison of Molecular Species 总被引:11,自引:10,他引:1
Mary C. Byrne Robert W. Ledeen Fred J. Roisen † Glee Yorke † Joseph R. Sclafani 《Journal of neurochemistry》1983,41(5):1214-1222
Abstract: Gangliosides were previously reported to induce neuritogenesis in primary neuronal cultures and in some neurally derived cell lines. Because isolated gangliosides usually contain variable quantities of peptides, we investigated the possibility the neurite-stimulating activity could be caused by these contaminants. Ganglioside preparations from bovine brain and other sources were subjected to a three-step purification procedure that eliminated at least 95% of the contaminating peptides. These purfied preparations retained their capacity to induce extensive neurite growth in neuro-2A murine neuroblastoma. Proteolytic digestion and a number of additional procedures were used to reduce residual contamination further without loss of activity. Several crude ganglioside samples had negative effects on neurite development until freed of theri inhibitory factors, which were derived from the tissue and/or introduced during laboratory operations. This was particularly evident for bovine white matter gangliosides whose activity increased in proportion to peptide removal. When carefully purified, virtually all of 11 different gangliosides tested were highly active, with the possible exception of GM4, which demonstrated only moderate activity in a limited number of tests. All of the neutral glycolipids tested, as well as sulfatides and free sialic acid, were inactive. 相似文献
40.
Properties of Hamster Embryo Fibroblasts Transformed In Vitro After Exposure to Ultraviolet-Irradiated Herpes Simplex Virus Type 2 总被引:53,自引:30,他引:23 下载免费PDF全文
An in vitro method which led to the transformation of hamster embryo fibroblasts after exposure to herpes simplex virus type 2 (HSV-2) inactivated with ultraviolet irradiation is described. The transformed cells (333-8-9) produced tumors when inoculated into newborn Syrian hamsters but not when injected into weanling Syrian hamsters of the same LSH inbred strain. However, after one in vivo passage, the 333-8-9 cells became highly oncogenic in weanling hamsters. No infectious virus was recovered from these cells. Herpes simplex virus antigens were detected in the transformed cells by the indirect immunofluorescence technique. Sera from tumor-bearing hamsters contained antibody with highly specific neutralizing activity against HSV-2. These studies indicate the continued involvement of the HSV-2 genome in an oncogenic cell line. 相似文献