Characterization of insulin receptors in primary cultures of quail (Coturnix coturnix japonica) oviduct cells. The level of insulin receptor is regulated by steroid and peptide hormones

1. We have characterized the insulin receptor in primary cultured quail oviduct cells and examined the hormonal regulation of its level. 2. We have also shown the recycling pathway of insulin receptors in the cultured cells using specific inhibitors (tunicamycin, chloroquine, monensin, and brefeldin A). 3. Our data suggest that glucocorticoids play important physiological roles in egg-white protein synthesis through increasing the number of insulin receptors and insulin through enhancing the transport of amino acids.     

Monoclonal antibodies against Pseudomonas aeruginosa elastase: a neutralizing antibody which recognizes a conformational epitope related to an active site of elastase.

We have established seven murine hybridoma cell lines which produce monoclonal antibodies (mAbs) against Pseudomonas aeruginosa elastase. The seven mAbs recognized at least six different epitopes on the elastase molecule. All mAbs inhibited both enzymatic activities of elastase and protease, in which elastin fluorescein and hide powder azure were used as substrates, respectively. One of them, mAb E-4D3, strongly neutralized enzymatic activities of peptidase in which furylacryloyl-glycyl-leucinamide was used as a substrate, as well as of elastase and protease. In contrast, the other six mAbs did not neutralize peptidase activity at all. The Ki value for furylacryloyl-glycl-leucinamide of E-4D3, as well as its Fab fragment, was comparable to those for metalloprotease inhibitors such as phosphoramidon and Zincov inhibitor. The binding of mAb E-4D3 was inhibited by phosphoramidon and Zincov inhibitor, but not by metal chelators such as EDTA and o-phenanthroline. A line of evidence suggests that mAb E-4D3 directly interacts with active site and highly neutralizes enzymatic activity of P. aeruginosa elastase. Data of Western blotting and ELISA suggest that mAb E-4D3 is likely to recognize an elastase molecule in a conformation-dependent manner as an epitope. In contrast, the neutralizing activity of the other mAbs against elastase and protease seems to be caused by a low accessibility of an enzyme to insoluble and high-molecular-mass substrates through the binding and steric hindrance of the mAbs to an enzyme.     

Human serum thyroglobulin determination with monoclonal antibody one-step assay: minimum interference of autoantibody

Combination of two thyroglobulin monoclonal antibodies (monoAbs) recognizing epitopes which are rarely recognized by an antibody enabled us to develop a rapid one-step enzyme immunoassay of serum Tg. Of 87 monoclonal antibodies, 20 were selected for the purpose. The method is a sandwich technique employing a monoAb covering microplate and horse-radish peroxidase monoAb conjugate. A combination of monoAb 7A7A solid phase and 31A2E for the conjugate gave the best results. The assay takes 60 min and the minimal detectable amount is 2 ng/ml. Intraassay variation is from 4 to 7%. Interassay variation is 5 to 12%. The recovery rate for Tg added to normal sera is between 89 and 111%. The correlation coefficient with the polyclonal antibody method in Tg hemagglutination negative sera is 0.98. The presence of autoantibody in sera up to 10 X 2(4) hemagglutination titer does not affect the recovery rate to a statistically significant extent.     

Calcium-activated adenosine triphosphatase activity of pellicles from Paramecium caudatum.

Pellicles were isolated from Paramecium caudatum for a study of the properties of its insoluble ATPase [EC 3.6.1.3] activity. Pellicular ATPase was solubilized by sonication and fractionated by sucrose density gradient centrifugation. The sedimentation coefficient of the ATPase was about 9S. The ATPase required Ca2+ for maximum activation. Addition of neutral salts to the assay medium inhibited the activity. Substrate specificity for ATP was low; other nucleoside triphosphates were hydrolyzed at about the same rate as ATP; AMP, pyrophosphate, and p-nitrophenyl phosphate were not hydrolyzed. The ATPase activity of the pellicle preparation had a pH optimum at pH 6.5, and a Michaelis constant of 9 micrometer. On the other hand, the enzymatic properties of the ATPase were somewhat modified by the procedure of solubilization and fractionation. The pellicular ATPase does not resemble ciliary dynein ATPase or the soluble ATPase of Tetrahymena.     

Lactate dehydrogenase isoenzymes are present in matrix vesicles

Matrix vesicles were isolated from epiphyseal growth plates of young rabbits. Lactate dehydrogenase activity was detected in the isolated matrix vesicles only in the presence of detergents, suggesting that NADH, the cofactor for the assay, does not penetrate the membrane of matrix vesicles. In contrast, the activity of alkaline phosphatase, a marker enzyme of the outer surface of matrix vesicles, was detected in the matrix vesicles using p-nitrophenyl phosphate as the substrate both in the presence and absence of detergents. Lactate dehydrogenase activity was detected only in the cytosol of chondrocytes of the epiphyseal growth plates but not in other subcellular fractions, showing that lactate dehydrogenase is not from the plasma membrane and membranes of intracellular organelles of chondrocytes. The isolated matrix vesicles contained all five lactate dehydrogenase isoenzymes but did not possess other cytosolic enzymes. These results show that lactate dehydrogenase is located in the matrix vesicles and suggest the presence of a mechanism for the specific uptake of cytosolic lactate dehydrogenase and the possibility of enzymatic quantification of the matrix vesicles at various calcification sites.     

Partial purification and characterization of a factor which stimulates an increase in ornithine decarboxylase activity in the liver from tumor cell-free ascites fluid

A factor responsible for stimulating an increase in ornithine decarboxylase activity in the liver of mice was found in tumor cell-free ascites fluid of mice 3 days after inoculation of tumor cells. The factor was purified about 70-fold in 25% yield from tumor cell-free ascites fluid. As little as 1 μg of protein of purified fraction, injected intraperitoneally into normal mice, significantly increased the activity of ornithine decarboxylase in the liver. The most active preparation of the factor formed two major protein bands on analytical polyacrylamide gel electrophoresis and both these bands stained with periodic acid-Schiff's reagent. The factor was a heat-labile, alkaline-stable, acidic protein with a molecular weight of more than 300 000. It was inactivated by treatment with 10 mM dithiothreitol, 5M urea, pronase or mixed glycosidase, but was stable on treatment with DNAase, RNAase or neuraminidase.     

The effects of estrogen, insulin and dexamethasone on the synthesis and secretion of egg white proteins in primary cultured oviduct cells of laying Japanese quail (Coturnix coturnix japonica)

1. The effects of estrogen, insulin and dexamethasone on the synthesis of egg white proteins were investigated by employing primary cultured oviduct cells of laying Japanese quails. 2. It was demonstrated that oviduct cells require insulin and dexamethasone, besides estrogen, to synthesize and secrete egg white proteins maximally.     

Isolation and characterization of recoverin-like Ca(2+)-binding protein from rat brain.

Rat brain was found, by immunoblot analysis, to have a protein of Mr 23,000 (P23k) that was clearly different from recoverin and was labeled with an antiserum raised against the NH2-terminus of recoverin. P23k could not be detected by an antiserum raised against the COOH-terminus of recoverin. Blots with 45Ca demonstrated that P23k bound Ca2+. This calciprotein was further purified by Ca(2+)-dependent hydrophobic interaction and ion-exchange chromatography. In SDS polyacrylamide gel electrophoresis, P23k had an apparent Mr of 21,000 in the presence of 10 microM Ca2+ and 23,000 in the absence of Ca2+ (0.1 mM EGTA). The isoelectric point of P23k was 5.6. Ca(2+)-binding analysis indicated that P23k bound 2 moles of Ca2+ per mole of protein and had two binding sites with dissociation constants of 13 microM and 0.2 microM. Purified P23k bound to the crude membrane fractions from the cerebellum, cerebrum and retina in a Ca(2+)-dependent manner. Partial amino acid sequence analysis of proteolytic fragments of P23k revealed the sequence homology between P23k and recoverin. These results suggested that P23k may act as a Ca(2+)-sensitive regulator by forming a complex with its target on the membrane.