Serologic methods for detection of Pasteurella multocida infections in nasal culture negative rabbits

An agar gel-diffusion test (AGDT) and an enzyme-linked immunosorbent assay (ELISA) were utilized to detect serum antibodies against Pasteurella multocida in naturally infected rabbits derived originally from a Pasteurella-free colony. The antigen used in both assays was purified from a serotype 3 (P-1059) strain of P. multocida. Among 47 serum samples tested 15 (32%) were seropositive; 12 (26%) of which were both AGDT and ELISA-positive, while 3 (6%) were ELISA-positive only. All rabbits examined were normal clinically and negative to repeated nasal cultures, but subsequent cultures at necropsy demonstrated the presence of P. multocida in 11 of the AGDT-positive rabbits and in 14 of the ELISA-positive rabbits. The organism was isolated most frequently from the naso-oropharynx and the tympanic bullae. Serotyping of isolates recovered from the nasopharynx were determined to be serotype 3 or 3,12. Ten seronegative rabbits also were necropsied and none were found harboring P. multocida. These preliminary data indicate that the application of an enzyme-linked immunosorbent assay may prove efficacious in identifying apparently healthy, consistently nasal culture-negative rabbits as subclinical carriers of P. multocida.     

Purification of natural human interferon-gamma by antibody affinity chromatography: analysis of constituent protein species in the dimers

A simple procedure for purifying human interferon-gamma from leukocytes was established, based on monoclonal antibody affinity chromatography. The recovery of interferon activity was essentially quantitative, and the specific activity of the product was (4-12) x 10(7) international units/mg protein. SDS-polyacrylamide gel electrophoresis reproducibly revealed four components associated with interferon activity (and no other proteins): two major ones with molecular weights (MW) of 24,000-25,000 (25K) and 19,000-20,000 (20K), a minor one with MW 14,000-15,000 (15K) (these three bands were doublets), and a still less prominent one(s) with MV 40,000-48,000. Gel filtration in neutral solution indicated that all the 25K, 20K, and 15K species exist as oligomers, probably dimers. By means of experiments using a cleavable crosslinking reagent, the dimers were shown to comprise both homo-and heterodimers. Gel filtration in alkali (the condition used during purification) indicated that the molecules are largely in a monomeric state. Thus, the molecules once dissociated in alkali appear to reassociate at random upon neutralization; this process takes place without being accompanied by inactivation.     

Subaxolemmal cytoskeleton in squid giant axon. II. Morphological identification of microtubule- and microfilament-associated domains of axolemma

In the preceding paper (Kobayashi, T., S. Tsukita, S. Tsukita, Y. Yamamoto, and G. Matsumoto, 1986, J. Cell Biol., 102:1710-1725), we demonstrated biochemically that the subaxolemmal cytoskeleton of the squid giant axon was highly specialized and mainly composed of tubulin, actin, axolinin, and a 255-kD protein. In this paper, we analyzed morphologically the molecular organization of the subaxolemmal cytoskeleton in situ. For thin section electron microscopy, the subaxolemmal cytoskeleton was chemically fixed by the intraaxonal perfusion of the fixative containing tannic acid. With this fixation method, the ultrastructural integrity was well preserved. For freeze-etch replica electron microscopy, the intraaxonally perfused axon was opened and rapidly frozen by touching its inner surface against a cooled copper block (4 degrees K), thus permitting the direct stereoscopic observation of the cytoplasmic surface of the axolemma. Using these techniques, it became clear that the major constituents of the subaxolemmal cytoskeleton were microfilaments and microtubules. The microfilaments were observed to be associated with the axolemma through a specialized meshwork of thin strands, forming spot-like clusters just beneath the axolemma. These filaments were decorated with heavy meromyosin showing a characteristic arrowhead appearance. The microtubules were seen to run parallel to the axolemma and embedded in the fine three-dimensional meshwork of thin strands. In vitro observations of the aggregates of axolinin and immunoelectron microscopic analysis showed that this fine meshwork around microtubules mainly consisted of axolinin. Some microtubules grazed along the axolemma and associated laterally with it through slender strands. Therefore, we were led to conclude that the axolemma of the squid giant axon was specialized into two domains (microtubule- and microfilament-associated domains) by its underlying cytoskeletons.     

Freeze denaturation of enzymes and its prevention with additives

Freeze inactivation of LDH, MDH, ADH, G-6-PDH, and PK and its prevention with additives such as sodium glutamate and albumin were studied. LDH, MDH, ADH, G-6-PDH, and PK, each lost their activity during frozen storage at -20 degrees C. The speed of the inactivation differed in each. The stability of the enzymes increased with the increase of the enzyme concentration. Sodium glutamate and albumin prevented the freeze inactivation. While the activity of the LDH solution frozen without additives was almost lost during a day of frozen storage, those frozen with either glutamate (0.2 M) or albumin (0.1%) added decreased less quickly. The residual activity after 1 day was 50% the initial prefreeze value for the former and 10% for the latter, respectively. Combined use of glutamate and albumin prevented the inactivation the best and maintained the initial activity almost completely over 6 weeks. The enzymes tested lost some part of their activity when their solutions were diluted by the media. This inactivation was prevented to a significant extent by the addition of sodium glutamate and/or albumin to the diluting media.     

Binding of macrophages and phospholipid flip-flop in supported lipid bilayers

Subclass-specific antibody-dependent interactions (binding and triggering) between macrophages and supported lipid bilayers have been studied. Percentages of mouse macrophage binding (J774 cell line) to the lipid bilayers were dependent on mouse monoclonal IgG subclasses. The efficiencies were as follows: IgG1 = IgG2a greater than IgG2b greater than IgG3. Furthermore, macrophage triggering (spreading) was more efficient on IgG2a- or IgG1-coated lipid bilayers than on IgG2a, IgG3, or non-specific rabbit IgG. The present experiments show also that phospholipid molecules are able to flip-flop from one side of a supported planar bilayer membrane to the other with a half-life of 10 h-1 day at 25 degrees C.     

Molecular species of platelet-activating factor generated by human neutrophils challenged with ionophore A23187

Two species of platelet-activating factor (PAF), 1-hexadecyl- and 1-octadecyl-2-acetyl-sn-glycero-3-phosphocholine (C16 = 0 AGEPC and C18 = 0 AGEPC) were detected in ionophore A23187-stimulated human neutrophils. The amount of AGEPC in 1 x 10(7) neutrophil cells was 80 +/- 26 pmol (mean +/- standard error) with a range of 14 to 223 pmol (n = 8), and it consisted of 80% of the C16 = 0 species and 20% of the C18 = 0 species. Most of the AGEPC derived from ionophore-treated neutrophils remained cell associated rather than being secreted into the medium, even when the medium contained ample albumin protein, which can trap AGEPC. These results were obtained by a technique of gas chromatography-mass spectrometry coupled with selected ion monitoring.     

Production of platelet-activating factor by washed rabbit platelets

Production of platelet-activating factor by washed rabbit platelets under stimulation with the ionophore A23187 was investigated utilizing two groups of platelet preparations. The first platelet preparation contained 0.03 +/- 0.02% contaminating white cells, while the second preparation contained 0.48 +/- 0.27% white cells. The latter preparation produced platelet-activating factor, mainly 1-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine, 8.3 +/- 6.3 pmol (mean +/- standard deviation) with a range of 2.6 to 21.4 pmol (n = 9), followed by small quantities of 1-octadecenyl- and 1-octadecyl-2-acetyl-sn-glycero-3-phosphocholine. In contrast, there was no production of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine by the former platelet preparation having 0.03% leukocytes. These quantitative analyses were carried out by the selected ion monitoring technique and it was concluded that it is necessary to consider the presence of contaminating white cells in studies on the production of platelet-activating factor by platelets.     

Suppressors of temperature-sensitive mutations in a ribosomal protein gene, rpsL (S12), of Escherichia coli K12

Summary Temperature-sensitive (ts) mutations were isolated within a ribosomal protein gene (rpsL) of Escherichia coli K12. Mutations were mapped by complementation using various transducing phages and plasmids carrying the rpsL gene, having either a normal or a defective promoter for the rpsL operon. One of these mutations, ts118, resulted in a mutant S12 protein which behaved differently from the wild-type S12 on CM-cellulose column chromatography. Suppressors of these ts mutations were isolated and characterized; one was found to be a mutation of a nonribosomal protein gene which was closely linked to the RNAase III gene on the E. coli chromosome. This suppressor, which was recessive to its wild-type allele, was cloned into a transducing phage and mapped finely. A series of cold-sensitive mutations, affecting the assembly of ribosomes at 20°C, was isolated within the purL to nadB region of the E. coli chromosome and one group, named rbaA, mapped at the same locus as the suppressor mutation, showing close linkage to the RNAase III gene.