Pathogenic fungal dynamics in a fall population of the blackmargined aphid (Monellia caryella)

A fall population of the blackmargined aphid, Monellia caryella (Fitch) (Homoptera: Aphididae), was monitored daily for mortality caused by fungi and parasitoids. Three species of Entomophthorales fungi were found. Fungal-induced mortality was found to be correlated with minimum temperature. During the period when the minimum temperature was consistently above 8°C, fungal-induced mortality was positively correlated with the sum of hours of leaf-wetness on days 5, 6, and 7 before sampling. Parasitoid wasps killed fewer hosts than fungi and were not affected by environmental factors.

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Résumé La mortalité quotidienne provoquée par des parasitoïdes et des champignons sur une population automnale de M. caryella Fitch (Homopt. Aphididae) a été suivie à Byron (Géorgie, USA), avec enregistrement de la température, de la pluie et de l'humidité des feuilles. 3 espèces de champignons entomophthorales ont été trouvées: Neozygites sp., Entomophthora planchoniana et Erynia sp. 54% des pucerons morts étaient contaminés par Neozygites et 46% par E. planchoniana. Seuls 2 pucerons avaient été tués par Erynia sp. Les taux de mortalité quotidienne par champignons s'élevaient après les périodes pluvieuses et d'humidité des feuilles. La mortalité due au parasitisme était inférieure à la mortalité due aux champignons et ne semblait pas liée aux conditions écologiques. La discussion porte sur l'importance de la mortalité provoquée par les champignons sur la dynamique de la population de pucerons.

     

Precursors in the biosynthesis of vasopressin and oxytocin in the rat. Characteristics of all the components in high-performance liquid chromatography.

A reverse-phase high performance liquid-chromatography (h.p.l.c.) protocol has been developed, whereby all the major known posterior-pituitary components that are derived from the processing of pro-oxytocin and pro-vasopressin can be separated one from another. Thus, in a single chromatographic step, it has been possible to separate vasopressin (VP), oxytocin (OT), oxytocin-neurophysin (rOT-Np), vasopressin-neurophysin (rVP-Np) and vasopressin-glycopeptide (rVP-GP) from acid extracts of the neurointermediate lobes of rat pituitary glands. All these peptides except rVP-GP were labelled in the neural lobe by 24h after a hypothalamic injection of [35S]cysteine, whereas all except VP were labelled by 24h after a similar injection of [3H]leucine. Three major labelled proteins were isolated from 20 min [35S]cysteine-injected rats when extracts of the supraoptic nucleus were subjected to Sephadex G-75 chromatography, h.p.l.c. and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Immunoprecipitation with antisera raised against rat neurophysins, VP and OT revealed 21000- and 19000-mol.wt. common precursors to VP and rVP-Np and a 15000-mol.wt. common precursor to OT and rOT-Np. Some immunoreactive rVP-Np could occasionally be detected in the Vo of Sephadex G-75 chromatograms of Wistar rat supraoptic-nucleus extracts, but no evidence of [35S]neurophysin in this fraction was obtained from h.p.l.c. fingerprinting of its S-carboxymethylated tryptic digests. Radioimmunoassay for rVP-Np and rOT-Np revealed that about 70-80% of the total recovered immunoreactive neurophysin (IR-Np) in the supraoptic nucleus eluted from Sephadex G-75 and h.p.l.c. in the positions of rVP-Np and rOT-Np. Evidence is presented for an approx. 20000-mol.wt. rOT-Np in both Wistar and Brattleboro rats and for an approx. 20000-mol.wt. component in the Brattleboro rat that is recognized by vasopressin-neurophysin antisera.     

Three-dimensional growth and morphogenesis of mouse submandibular epithelial cells in serum-free primary culture

Mouse submandibular epithelial cells can be grown in primary culture using the collagen gel matrix and a chemically defined medium consisting of insulin, transferrin, cholera toxin, and BSA (or FGF). Sustained cell growth leading to a 5–10-fold increase in cell number was observed in less than 2 weeks. In the presence of these additives, clumps of cells proliferate by extending ‘star-like’ projections into the matrix, resulting in three-dimensional outgrowths. The morphology of these outgrowths can be modulated to form a ‘cyst-like’ appearance by deleting BSA and adding cortisol to the basal medium containing insulin, transferrin, cholera toxin and FGF. In brief, a serum-free medium for sustained growth has been devised and a simple manipulation of supplements can modulate the three-dimensional colony morphology in the collagen gel matrix. Finally, the resulting outgrowths can produce epidermal growth factor (EGF) in response to dihydrotestosterone.     

Primary culture of mouse mammary tumor epithelial cells embedded in collagen gels

Summary Mammary tumor epithelial cells from BALB/cfC3H mice were dispersely embedded inside the collagen gels in Ham's F-12 medium containing horse serum. A sustained cell growth leading to a 5- to 10-fold increase in cell number over initial level was observed in less than 2 weeks. The extent of this growth was found to be dependent on serum concentration. However, addition of various protein and steroid hormones, both singly and in combination, to low-serum-containing medium failed to achieve a comparable level of growth to that promoted by higher serum concentration. Mammary tumor cells can now be consistently propagated in primary culture. This investigation was supported by Grants CA05388 and CA09041 awarded by the National Cancer Institute, Department of Health, Education and Welfare, and by cancer research funds of the University of California.     

Sexual differences in the incidence and severity of ectoparasitic infestation of the brown trout, Salmo trutta L.

Hatchery-reared and wild brown trout, Salmo trutta L., were examined for skin ectoparasites during their spawning period in 1977 and 1978. A total of eight genera of parasites, comprising five ciliates, one flagellate, one monogenean and one parasitic fungus, were identified with as many as five different genera occurring on a single fish. Sexually mature male fish were more frequently or more severely infested by species of Ichthyophthirius, Scyphidia, Gyrodactylus and Saprolegnia than were immature fish of either sex or mature female fish. The differences in ectoparasitic loading could not be correlated with known, seasonal changes in the mucus-producing potential of the epidermis. These findings are discussed in relation to the defence mechanisms of teleost fish and to some of the endocrinological changes that occur in salmonid fish during the spawning season.     

Trace analysis of the MIF analogue pareptide in blood plasma by high-performance liquid chromatography and short-wavelength excitation fluorometry

A high-performance liquid chromatographic procedure was developed and applied to analysis of the pharmacologically active MIF analogue pareptide in human plasma. The procedure involves formation of a fluorescent 7-chloro-4-nitrobenzyl-2-oxa-1,3-diazole-(NBD-CI) pareptide derivative followed by separation of the NBD derivative from plasma components on a 30-cm microparticle octadecylsilane bonded column. The separated derivative was quantitated using a short-wavelength excitation fluorometric detector. The detection limit of pareptide in plasma samples was 5 ng or 17 pmoles per ml of plasma. In the absence of plasma, the corresponding on-column detection limit was 0.5 pmoles.     

A cytological study of micronuclear elongation during conjugation in Tetrahymena

Micronuclear elongation is the first major event in a series of nuclear changes occurring during the sexual stage of the life cycle of Tetrahymena. Beginning at about one hour after cells of complementary mating types have conjugated, the micronucleus leaves its recess in the macronucleus and swells slightly. This is accompanied by a reorganization of its chromatin from a reticular to a solid body. In the next stage the micronucleus assumes an egg shape, a development concomitant with the appearance of microtubules. While the chromatin spins out from the dense body, and microtubules increase in number, the nucleus assumes a spindle shape. During the elongation, which increases the length of the nucleus some fifty fold, microtubules are prominent in clusters just internal to the nuclear membrane, and parallel to the longitudinal axis of the nucleus. When elongation is completed the nucleus is curved around the macronucleus. Internally, partially condensed strands of chromatin are located off-center, towards the macronuclear side, and the density of the microtubules is diminished. At all the stages, DNA is located throughout the nucleus; neither discrete chromosomes nor synaptonemal complexes are seen. Occasionally cytoplasmic membrane systems are seen fused to the nuclear envelope which retains the typical appearance of a double membrane with pores.     

Isoperoxidases from tobacco tissue cultures

Two anodic isoperoxidases (A₁ and A₂) from tobacco tissue culture W-38 and two cathodic isoperoxidases (C₃ and C₄) from tobacco suspension culture WR-132 have been separated and characterized. Molecular weights for each of the isoperoxidases have been determined by two different methods. Only C₄ contained a carbohydrate component. The substrate specificity and the pH optima for the four enzymes with each of five substrates were determined.