Observations on the use of solid-phase-coupled antibodies in the radioimmunoassay of human placental lactogen

A detailed comparative assessment was made of the use of solid-phase-coupled antibodies in radioimmunoassay, by using an assay for human placental lactogen as a model system. The major advantages of the solid-phase technique are: (1) in common with the use of a second antibody, it is universally applicable; (2) separation can be carried out rapidly; (3) in contrast with some other techniques, the separation of antibody-bound and free antigen is virtually complete. The disadvantages when compared with other procedures are: (1) a considerable proportion of the antibody may be lost during the initial coupling reaction; (2) the tubes must be continuously mixed during incubation, and much effort is expended in removing and replacing the caps; (3) there is a decrease in the apparent affinity constant of the antibody after coupling, which is reflected in a lower sensitivity of the assay system. It is concluded that solid-phase antibodies are of greatest value in those systems in which the supply of antiserum is abundant, and in which the achievement of high sensitivity is not a requirement.     

Damage and performance of the green spruce aphid, Elatobium abietinum on twenty spruce species

Field and laboratory observations of the relationships between the performance of Elatobium abietinum (Walker), Homoptera, Aphididae, and various species of spruce were undertaken from January 1980 to April 1981. The study included sampling for aphids in established field plots of spruce during May and June respectively before and after the migration period in spring. The aphid's performance (weight and mean relative growth rate) at different seasons on pot grown plants of selected spruce species was monitored, covering, in all, 20 species of spruce.Aphid performance was greatest on the North American spruces, especially Picea sitchensis (Bong) Carr and P. mexicana Martinez; the Asian spruces were the least favoured, especially P. glehnii (Schmidt) Mast. Between these two geographical groups the Eurasian spruce species (sensu Wright, 1955) demonstrated an intermediate aphid performance.

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Résumé Les observations dans la nature et au laboratoire sur les performances d'E. abietinum Walker et différentes espèces d'épicéas ont été effectuées de janvier 1980 à avril 1981. Les observations dans la nature comprenaient des prélèvements de pousses d'épicéa pour dénombrer les pucerons avant (mai) et après (juin) la période de migration du printemps. Les performances des pucerons (poids et taux moyen de croissance relative) ont été examinées à différentes saisons sur des plantes en pot sur un total de 20 espèches sélectionnées d'épicéas.Les performances du puceron ont été supérieures sur les espèces d'épicéa de l'Amérique du nord Picea sitchensis et P. mexicana; les espèces asiatiques étaient les moins favorables, particulièrement P. glehnii. Entre ces deux groups géographiques, les espèces eurasiennes (sensu Wright, 1955) ont permis des performances intermédiares chez les pucerons.

     

Opsonization with Antimyelin Antibody Increases the Uptake and Intracellular Metabolism of Myelin in Inflammatory Macrophages

In most demyelinating diseases, macrophages are believed to be active agents of myelin destruction. In experimental encephalomyelitis, these cells appear to strip off and ingest the myelin lamellae, and myelin debris has been observed within the cell body. We show here in vitro conditions in which rat peritoneal macrophages phagocytose and metabolize CNS myelin lipids. Purified rat myelin, prelabeled in vivo with [14C]acetate, was incubated with preimmune serum or rabbit antiserum to rat CNS myelin and added to macrophage monolayers. Myelin opsonized with antimyelin antibodies was more readily phagocytosed and metabolized by cultured macrophages than untreated myelin or that preincubated with preimmune serum. In the presence of macrophages, levels of myelin polar lipids and cholesterol decreased, whereas radioactive cholesterol ester and triglyceride accumulated. Up to five times as much radioactive cholesterol ester and about twice as much triglyceride accumulated in macrophage cultures containing antibody-treated myelin as in cultures fed preimmune serum-treated myelin or in those incubated with untreated myelin. Both the fatty acid and the cholesterol from cholesterol ester contained radioactive label; therefore, both were derived at least partly from the radioactive myelin lipid. Antiserum to myelin purified from peripheral nerve was almost as effective as that to CNS myelin in stimulating cholesterol metabolism, whereas antiserum to galactocerebroside was about 70% as active. Antiserum to basic protein had less effect, whereas antiserum to the myelin-associated glycoprotein and proteolipid protein was inactive. Of the polar lipids, ethanolamine phosphatide was most degraded in both the antiserum- and preimmune serum-treated myelin, with the diacyl form and plasmalogen form degraded about equally. These experiments indicate that myelin-specific antibodies in inflammatory CNS lesions may participate in and stimulate macrophage-mediated demyelination.     

Immunocytochemical localization of S-100 protein in stellate cells (folliculo-stellate cells) of the adenohypophysis in the monkeys Macaca irus and Cercopithecus aethiops

Summary With the use of an antibody against bovine S-100 protein, it was possible to reveal a characteristic cell type in the pars distalis and the pars tuberalis of the monkey Macaca irus. In the adenohypophysis of Cercopithecus aethiops, labeled cells were present in the pars distalis, pars tuberalis, and pars intermedia. These cells, so-called folliculo-stellate cells, were found in all pituitaries studied. Surprisingly, an antibody against human S-100 protein did not label the stellate cells of the adenohypophysis. However, in Macaca irus, this antibody gave a strong positive reaction with various other cell types (interstitial cells of the pineal gland, Müller cells of the retina, autonomic ganglionic cells, glial cells of the central nervous system, Schwann cells, Bergmann glia of the cerebellum, fat cells, reticular cells of lymphoid organs). By use of double immunoenzymatic labeling, it was evident that stellate cells are spatially related either to somatotropes, prolactin cells, corticotropes, or to glycoprotein-containing cells. Thus, a specific relationship to a particular endocrine-cell type could not be observed.Dr. M.P. Dubois died in Tours (France) on March 30, 1986, aged 65     

DNA polymorphism related to the idiopathic hemochromatosis gene: evidence in a recombinant family

Summary The metabolic error involved in idiopathic hemochromatosis, as well as the underlying genetic defect remain unknown. It has, however, been recently shown that this genetic lesion occurs at a locus linked to the major histocompatibility complex, probably close to the HLA-A locus, and that the disease is recessively transmitted. Therefore, in a family where one subject has idiopathic hemochromatosis his HLA-identical siblings should also be affected. We present here the restriction polymorphism with two MHC class I probes and one DR probe in an exceptional family with three HLA-identical siblings: one (the proband) has a major form of idiopathic hemochromatosis, while the other two are free of any clinical or biochemical signs of the disease. The restriction patterns observed after DNA digestion by enzymes EcoRI, EcoRV, BglII, BamHI, PvuII, TaqI, HincII, and HindIII led to the conclusion that one of the proband's chromosome 6 had undergone two alterations: one, a deletion in the DR region, was revealed by missing fragments all correlated with DR5; the other was an unbalanced cross-over or a genetic conversion in the MHC class I region. This latter alteration was revealed by modifications in the patterns of high molecular weight HindIII bands which hybridize with probe pHLA2 and also by the absence of a HindIII fragment of 7.4 kb hybridized by another class I probe. This latter alteration most likely involved the hemochromatosis gene and could be the first step toward a molecular approach to this gene.     

The role of phospholipases from inflammatory macrophages in demyelination

Activated macrophages harvested from rat peritoneum were shown to contain phospholipase A₁, A₂ and lysophospholipase activities which were defined on a series of radiolabelled phospholipid substrates. During in vitro culture of these elicited macrophage populations, phospholipase enzymes were secreted into the culture medium. Radiolabelled myelin, prepared from young rats after intracerebral injection of¹⁴C acetate, was used as a substrate to analyze the susceptibility of central nervous system (CNS) myelin to attack by cell-associated and secreted macrophage enzymes. Homogenates of peritoneal macrophages degraded the myelin lipids at acid pH; phosphatidyl choline (PC) and ethanolamine phosphatide (EP) were both degraded with liberation of free fatty acid and small amounts of lysolipids. The ethanolamine lipids were most vulnerable; up to 20% of this fraction was degraded in six hours. Selected batches of macrophage culture supernatant similarly degraded the myelin EP at acid pH. These results suggest that phospholipase enzymes, released from activated macrophages in close proximity to the myelin sheath, may participate in primary demyelination in inflammatory CNS lesions.     

Sensory receptors involved in the feeding behaviour of the rotifer Asplanchna brightwelli

A study of the anterior sensory receptors of male and female Asplanchna brightwelli by scanning electron microscopy reveals some important differences in the region surrounding the mouth. In the male, the ventrolateral sensory bristles, the pseudotrochus, the inner and the outer buccal tufts and the mastax receptors are absent. The oral receptors are reduced. Transmission electron microscopy of these receptors shows that they consist of ciliated sensory cells surrounded by epithelial supporting cells. The distal ends of the cilia of the mastax receptors are modified; the cilia of the other receptors differ only in their length and rootlet structure from the locomotor cilia of the cingulum. A consideration of the feeding behaviour of Asplanchna leads us to suppose that these sensory cilia function in mechanoreception and in chemoreception.     

A CNBR peptide located in the middle region of diphtheria toxin fragment B induces conductance change in lipid bilayers: Possible role of an amphipathic helical segment

Conductance measurements on planar lipid bilayers demonstrate that CB1, a CNBr peptide of diphtheria toxin fragment B located in its middle region, possesses the unique property to destabilize the lipid bilayer organization. It is suggested that a segment of 25 amino acids in the N-terminal sequence of CB1 could be responsible for this effect. Its very low polarity, its predicted amphipathic helical structure and a helix length corresponding to the thickness of the hydrocarbon region of the lipid bilayer should specifically favor its insertion in the membrane. The existence of such a transverse lipid-associating domain could confer upon the molecule the properties leading to the anchoring of diphtheria toxin in the cytoplasmic membrane.     

pdsA, a gene involved in the production of active phosphodiesterase during starvation of Dictyostelium discoideum amoebae

Summary Upon starvation, amoebae of the mutant strain HPX235 are unable to aggregate. Previous work has shown that this aggregateless character was associated with a nearly complete block in the production of the phosphodiesterase by these cells. Aggregation of the HPX235 amoebae can be induced with exogenous phosphodiesterase. In the present work, we show that both the aggregateless character and the block in phosphodiesterase production appear to result from the same recessive mutation, allocated to I.g.IV. Two other mutant strains displaying a comparable phenotype (HPX262 and HP594) were shown by complementation to belong to the same locus pdsA. Unlike wild type cells, the mutants of the locus pdsA cannot be induced to produce phosphodiesterase following treatment of the cells with exogenous cAMP, whether exogenous phosphodiesterase is present or not in the starvation buffer. It is concluded that pdsA is either the structural gene for the phosphodiesterase or a controlling element whose integrity is required for phosphodiesterase production. Mutations in pdsA share secondary effects among which the abnormally low production of the phosphodiesterase inhibitor. However, this effect can be overcome upon addition of exogenous phosphodiesterase, and most likely results from the lack of cAMP hydrolysis.The late development is also affected in pdsA mutants. Aggregates formed in the presence of exogenous phosphodiesterase cannot culminate normally. This suggests that the level of cAMP hydrolysis also plays a role during the late stages of development of Dictyostelium discoideum.Abbreviations used cAMP adenosine 3,5-cyclic monophosphoric acid - l.g. linkage group - PDE 3,5-cAMP phosphodiesterase