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1.
FJ Grommers 《Canadian Metallurgical Quarterly》1993,118(6):207-212
The intrinsic value of animals and their place in human society influence veterinary practice. The role-responsibility of the veterinarian is under pressure of practical circumstances, client requests and constraints of breeding and management systems. A reflection on human needs as related to the intrinsic value and welfare of animals, is required inside and outside the profession. It is in the interest of life to think and act out of total ecological concepts. In order to be better prepared to deal with ethical problems in practice, students should receive adequate training. The assumed value-free research and the need for outside financial support are a hindrance for research projects that aim at sustainability of human and animal life. It is concluded that the profession needs a philosophy about her objectives. 相似文献
2.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), and benz[a]anthracene (BA) highly induce cytochrome P4501A1, determined by aryl hydrocarbon hydroxylase (AHH) activity, in human hepatoma HepG2 cells within 24 h. AHH activity induced by TCDD and TCDF persists for at least 48 h. In contrast, AHH activity induced by BA rapidly declines, although the amounts applied are 4-5 orders of magnitude higher than those of TCDD or TCDF. AHH induction in HepG2 cells differs from that in rat hepatoma cells H4IIEC3/T in two aspects: (1) HepG2 cells are 20 times less sensitive to the test compounds than H4IIEC3/T cells. (2) TCDF-induced AHH activity does not persist in the rat cells. The results suggest that human HepG2 cells, because of their low sensitivity, are inferior to rat H4IIEC3/T cells for determining TCDD equivalents in environmental samples. They may be useful for investigating species dependent differences in the toxicokinetics of individual polyhalogenated aromatic hydrocarbon congeners. 相似文献
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Neurotensin (NT) was isolated from an extract of the intestine of the cane toad, Bufo marinus and its primary structure established as: pGlu-Ala-Ile-Val-Ser-Lys-Ala-Arg-Arg-Pro-Tyr-Ile-Leu. This amino acid sequence shows five substitutions (Leu2 --> Ala, Tyr3 --> Ile, Glu4 --> Val, Asn5 --> Ser, and Pro7 --> Ala) compared with bovine NT. Synthetic Bufo NT (pD2 = 8.05 +/- 0.28) was equipotent and equally effective as bovine NT (pD2 = 8.24 +/- 0.38) in producing spasmogenic contraction of isolated segments of toad small intestine. However, the maximum response produced by Bufo NT was only 35 +/- 2% of that produced by substance P. The potencies, but not the maximum responses, to Bufo and bovine NT were significantly (p < 0.05) attenuated by pre-treatment with atropine but neither parameter was significantly diminished by tetrodotoxin and indomethacin. The data suggest that the action of NT involves interaction with receptors on toad intestinal smooth muscle that recognize the C-terminal region of NT (residues 8-13) that has been fully conserved during evolution of tetrapods. Contractile activity is mediated, at least in part, by release of acetylcholine. 相似文献
5.
Molecular modeling of immunoglobulin light chains implicates hydrophobic residues in non-amyloid light chain deposition disease 总被引:3,自引:0,他引:3
Deret S; Chomilier J; Huang DB; Preud'homme JL; Stevens FJ; Aucouturier P 《Protein engineering, design & selection : PEDS》1997,10(10):1191-1197
Light chain deposition disease is a severe complication of certain
immunoproliferative disorders, due to the secretion of a monoclonal light
chain which precipitates close to basement membranes of several tissues. A
kappa isotype restriction and an unusual frequency of a variable region
subgroup (VkappaIV) suggest that precise structural features govern the
propensity of pathogenic light chains to precipitate in extracellular
spaces. We studied primary structures of light chains from six patients
with light chain deposition disease in comparison with light chains from
other pathological conditions. Sequence alignment revealed the presence of
certain amino acids only in light chain deposition disease, in particular
non-polar replacing hydrophilic residues. To determine the role of these
residues, structures of the variable domain from four kappa chains
belonging to VkappaI and VkappaIV subgroups responsible for deposition
disease were modeled using known immunoglobulins as templates. The most
evident structural features shared by all pathogenic light chains were
hydrophobic residues exposed to the solvent in complementarity determining
regions 1 or 3. In contrast to immunoglobulin light chain- related
amyloidosis, where deposition of organized material might be due to
electrostatic interactions between light chain dimers, hydrophobic
interactions could enhance amorphous precipitation in non- amyloid light
chain deposition disease.
相似文献
6.
Monodisperse FePt nanoparticles with size of 4.5 and 6.0 nm were prepared by simultaneous reduction of platinum acetylacetonate
and thermal decomposition of iron pentacarbonyl in benzylether. The crystallography structure, size, and composition of the
FePt nanoparticles were examined by X-ray diffraction and transmission electron microscopy. Energy dispersive X-ray spectrometry
measurements of individual particles indicate a broad compositional distribution in both the 4.5 and 6 nm FePt nanoparticles.
The effects of compositional distribution on the phase-transition and magnetic properties of the FePt nanoparticles were investigated. 相似文献
7.
STUDY DESIGN: Iliac crest corticocancellous allografts for anterior interbody fusion were harvested from six cadavers. The grafts were cut sequentially from left and right crests and randomly assigned to tricortical or bicortical preparations. Their compression strengths then were determined and compared by matched pair analysis. OBJECTIVES: To quantify the failure strength of the grafts from different iliac locations and determine the optimal type of preparation of the grafts for anterior interbody fusion. SUMMARY OF BACKGROUND DATA: Iliac crest corticocancellous autografts and allografts commonly are used for interbody cervical fusions. However, graft strengths for specific sites have not been determined fully. METHODS: Six paired, fresh frozen, iliac crests were sectioned using a customized miter box into multiple 1-cm-thick grafts 1.5 cm in depth to simulate cervical interbody grafts. The left and right sides of each pair were randomly assigned to tricortical and bicortical preparations. The samples were tested by applying a compressive load to failure using a specialized fixture to simulate vertebral body loading. RESULTS: The grafts closer to the anterosuperior iliac spine had significantly higher failure loads and failure strengths than those closer to the posterosuperior iliac spine. The strengths of the bicortical grafts were 72 +/- 14% of the strengths of the tricortical grafts (P < 0.001). CONCLUSIONS: Anterior iliac crest grafts were stronger in compression, even after removal of one cortical surface, than posterior iliac crest grafts. 相似文献
8.
JC van der Voet RB Keus AA Hart FJ Hilgers H Bartelink 《Canadian Metallurgical Quarterly》1998,42(2):247-255
Low frequency impedance measurements of pure egg lecithin (phosphatidylcholine) bilayers have revealed the presence of four layers which can be attributed to the acyl chain, carbonyl, glycerol bridge and phosphatidylcholine regions of the lecithin molecule. Measurements on bilayers formed in the presence of unoxidised-cholesterol revealed that cholesterol molecules were located in the hydrocarbon region of the bilayer with its hydroxyl groups aligned with the carbonyl region of the lecithin molecules. Measurements of oxidised-cholesterol lecithin bilayers revealed that these molecules protruded less into the hydrocarbon region and their polar hydroxyl group aligned with the glycerol bridge region of the lecithin molecule. 相似文献
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