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21.
Chimeric Fc receptors, consisting of the IgG-binding domains of both staphylococcal protein A and streptococcal protein G, were constructed. An efficient bacterial expression system was used to produce the recombinant proteins, which vary in size and number of IgG-binding domains. The purified receptors were analyzed by immunodiffusion and a competitive enzyme-linked immunosorbent assay to establish the relative binding strength to various polyclonal and monoclonal immunoglobulins from different species. The results demonstrate that protein A and protein G have complementary binding patterns and that the chimeric receptors retain the binding capacities of both the parental constituents. This suggests that these novel chimeric receptors might be versatile reagents for immunochemical assays.  相似文献   
22.
Hilali  M.  Lindberg  R.  Waller  T.  Wallin  B. 《Acta veterinaria Scandinavica》1986,27(4):623-625
A female racing greyhound dog was presented to the clinic at the age of 3 months with a 2 months’ history of irregular hindleg movements and thin hindleg muscles. On examination 1 month later, a squatting standing posture, a week proprio-ceptive positioning reaction, and severe atrophy and pain of the lumbar and thigh muscles, were evident. The dog was sacrificed and necropsied. The adrenals, hindleg muscles, kidneys, myo-cardium, peripheral nerves, spinal cord, thyroid, and tonsils were fixed in 10 % neutral buffered formalin and processed for histo-pathology.  相似文献   
23.
Steady state kinetics were used to examine the influence of Cd2+ both on K+ stimulation of a membrane-bound ATPase from sugar beet roots (Beta vulgaris L. cv. Monohill) and on K+(86Rb+) uptake in intact or excised beet roots. The in vitro effect of Cd2+ was studied both on a 12000–25000 g root fraction of the (Na++K++Mg2+)ATPase and on the ATPase when further purified by an aqueous polymer two-phase system. The observed data can be summarized as follows: 1) Cd2+ at high concentrations (>100 μM) inhibits the MgATPase activity in a competitive way, probably by forming a complex with ATP. 2) Cd2+ at concentrations <100 μM inhibits the specific K+ activation at both high and low affinity sites for K+. The inhibition pattern appears to be the same in the two ATPase preparations of different purity. In the presence of the substrate MgATP, and at K+ <5 mM, the inhibition by Cd2+ with respect to K+ is uncompetitive. In the presence of MgATP and K+ >10 μM, the inhibition by Cd2+ is competitive. 3) At the low concentrations of K+, Cd2+ also inhibits the 2,4-dinitrophenol(DNP)-sensitive (metabolic) K+(86Rb+) uptake uncompetitively both in excised roots and in roots of intact plants. 4) The DNP-insensitive (non metabolic) K+(86Rb+) uptake is little influenced by Cd2+. As Cd2+ inhibits the metabolic uptake of K+(86Rb+) and the K+ activation of the ATPase in the same way at low concentrations of K+, the same binding site is probably involved. Therefore, under field conditions, when the concentration of K+ is low, the presence of Cd2+ could be disadvantageous.  相似文献   
24.
The performance of The Subhuman Primate Pregnancy Test Kit was evaluated for routine detection of early (days 19-21) pregnancy in the rhesus monkey. Out of 123 confirmed matings, 19 resulted in pregnancy. In the pregnant animals the kit had an accuracy of 73.7%. In the nonpregnant females the accuracy was higher, 88.5%. False positives were encountered in ovariectomized females as well as adult intact males.  相似文献   
25.
Abstract Hybrid cell lines producing monoclonal antibodies with specificity for the lipopolysaccharide (LPS) from the deep rough mutant Salmonella minnesota R595 have been established. Spleen cells from BALB/c mice immunized with live R595 bacteria were fused with Sp 2/0 myeloma cells and three hybridomas producing antibodies specific for heptoseless LPS from Salmonella were selected. All three monoclonal antibodies were shown to bind only to heptoseless, but 3-deoxy- d -manno-octulosonic acid (KDO) containing LPS when tested in enzyme-linked immunosorbent assay (ELISA) against a set of structurally defined LPS and lipid A from Salmonella, Shigella and Escherichia coli . Synthetic KDO was an efficient inhibitor of the antibody-R595 LPS interaction defining that KDO is in an immunodeterminant position interacting with the monoclonal antibodies.  相似文献   
26.
Two shuttle vectors containing the gene for protein A (spa) from Staphylococcus aureus have been constructed to study expression of the gene in various strains of S. aureus and in the coagulase-negative species Staphylococcus epidermidis, Staphylococcus capitis, and Staphylococcus xylosus. One plasmid, pSPA15, contains the complete structural gene for protein A, which binds to the cell wall in various Staphylococcus species. The other plasmid, pSPA16, codes for a truncated protein A lacking the C-terminal part called region X. The latter is exclusively extracellular in all Staphylococcus species tested, which confirms the importance of region X for cell wall binding. The expression of the plasmid-coded protein A in various strains of S. aureus is strongly correlated to the expression of the chromosomal spa gene. The coagulase-negative species expressing plasmid-encoded protein A produce 12 to 30% of the amount coded by the chromosomal spa gene in S. aureus strains Cowan I and A676.  相似文献   
27.
Extracellular RNase N4 from Neurospora crassa is derepressible by limitation of any of the three nutrient elements obtainable from RNA. We have purified and characterized the enzyme from cultures grown under each of the three states of derepression. The purification procedure consisted of an ultrafiltration step, cation-exchange chromatography, and gel filtration. We found only one enzyme (N4) that hydrolyzed RNA at pH 7.5 in the presence of EDTA in culture filtrates from nitrogen-, phosphorus-, or carbon-limited cells. In all three cases, the enzymes were identical by polyacrylamide gel electrophoresis (Mr approximately 9,500) and by gel filtration (Mr approximately 10,000). There were no differences in thermal stability or pH optimum; all three cross-reacted with antibody to the nitrogen-depressed enzyme in interfacial ring and in Ouchterlony tests. Digestion of homopolyribonucleotides indicated that N4 preferentially cleaved phosphodiester bonds adjacent to guanine residues. Results indicate that the enzymes are very similar or identical and are probably products of the same gene. N4 appears to be homologous to guanine-specific RNases from other fungal sources.  相似文献   
28.
Addition of 15L-hydroperoxy-5,8,11,13-eicosatetraenoic acid (15-HPETE) to human leukocytes led to the formation of a novel series of compounds containing four conjugated double bonds. The yield of tetraenes was increased approx. 100-fold when ionophore A23187 (5 μM) was added simultaneously with 15-HPETE. The structure of the major tetraene was established by physical methods as well as by chemical degradation and found to be 5,6,15L-trihydroxy-7,9,11,13-eicosatetraenoic acid.  相似文献   
29.
30.
Summary The distribution and characterization of the opioid octapeptide met5-enkephalin-arg6-gly7-leu8 (met5-enk-arg6-gly7-leu8) within the gastrointestinal tract of the rat has been determined by immunohistochemistry and radioimmunoassay by use of a newly developed antibody to met5-enk-arg6-gly7-leu8. With both techniques, met5-enk-arg6-gly7-leu8-immunoreactivity (met5-enk-arg6-gly7-leu8IR) was detected in all regions of the gastrointestinal (GI) tract except the esophagus. The highest concentration of immunoreactive met5-enk-arg6-gly7-leu8 was observed in the colon, while intermediate concentrations were found in the stomach, duodenum, jejunum, and ileum. Immunostained somata were observed chiefly in the myenteric plexus; immunostained processes were present primarily in the myenteric plexus and the circular muscle layer. This distribution pattern is similar to that previously observed with antiserum to met5-enkephalin-arg6-phe7 (met5-enk-arg6phe7). Chromatographic analysis of met5-enk-arg6-gly7leu8-immunoreactive peptides extracted from the GI tract revealed the presence of an immunoreactive peptide of high molecular weight which accounted for approximately three-quarters of met5-enk-arg6-gly7-leu8-IR in both stomach and colon. These findings suggest a role for peptides related to the octapeptide met5-enk-arg6-gly7-leu8 in the regulation of GI function.  相似文献   
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