Dominance of colchicine resistance in hybrid CHO cells

Intraspecific hybrids of colchicine-sensitive with colchicine-resistant (CHR) Chinese hamster ovary cells were constructed, using six different colchicine-resistant clones from two independent series. In each instance, colchicine resistance was expressed in an incompletely dominant manner. Some hybrid clones were examined further for the expression of the pleiotropic CHR phenotype and for the cell surface P glycoprotein. These features of the colchicine-resistant phenotype were also expressed coordinately.     

Interactions between the diatom Thallasiosira pseudonanna and an associated pseudomonad in a mariculture system.

The marine diatom Thallasiosira pseudonanna (3H) and several bacteria associated with it were isolated from batch cultures at the University of Delaware mariculture facility. The interaction between the algae and each of the bacteria was investigated. One of the isolates, T827/2B (Pseudomonas sp.), was incapable of surviving in f/2 culture medium unless the algae were present. When the algae and T827/2B were grown together in the f/2 medium, the bacterial growth was stimulated and the algal growth was inhibited. Bacterial filtrate had a similar effect on the algae, indicating that the bacterial effect is an indirect one most likely resulting from the excretion of a harmful compound into the medium. Preliminary characterization of the material excreted by the bacteria indicates that it s proteinaceous in nature. The interactions observed does not fit into any single category of interactions but can be explained as a combination of competition and indirect parasitism.     

The isolation of "link proteins" from bovine nasal cartilage

Methods of isolating the water insoluble 'link proteins' from preparations of bovine nasal cartilage proteoglycan aggregates have been investigated. Upon chromatography on Sepharose 4B in 0.1% sodium dodecyl sulfate, the 'link proteins' are found in a discrete, included peak, whereas the bulk of the proteoglycan emerges at the void volume. Some low molecular weight proteoglycan is associated with the 'link proteins'. An alternative procedure, i.e. chromatography on DEAE-cellulose in sodium dodecyl sulfate, has also been examined. In 0.1% sodium dodecyl sulfate, proteoglycan monomer is not absorbed by the column, whereas 'link proteins' are. Subsequently, the 'link proteins' with a minor fraction of the proteoglycan are eluted with 1.0% sodium dodecyl sulfate. Both procedures serve to separate the 'link proteins' from the bulk of proteoglycan present in an aggregate preparation, but additional steps are necessary to achieve homogeneity. Thus a 'link protein' preparation, fractionated from proteoglycan aggregate by equilibrium density gradient centrifugation under dissociative conditions, can be finally purified by chromatography on DEAE-cellulose in sodium dodecyl sulfate.     

The population dynamics of the millipede, Ommatoiulus moreletii(Diplopoda: Iulidae)

The population dynamics of Ommatoiulus moreletii were studied in an open grassland and a dry sclerophyllous woodland in South Australia. During summer, O. moreletii aggregated in cool, moist sites (e.g. beneath tussocks of Lomandra fibrata (Liliaceae)) or burrowed underground. In autumn, the animals surfaced and dispersed. In a particularly hot and dry summer, mortality was demonstrated in the grassland but not in the woodland which was relatively cooler and moister. The survival of females from an autumn breeding season to the subsequent spring was inversely correlated with their maturity in autumn. The advantage to O. moreletii of survival of females after a poor breeding season is discussed with reference to den Boer's (1968) concept of "spreading of risk".     

Evidence for conformeric states of Rhodopsin

Spectrophotometric measurements of metarhodopsin II appearance are made on five different kinds of rhodopsin preparations. Although the preparations differ greatly in their rhodopsin: phospholipid ratio, the meta II kinetics in all of them are strikingly similar in certain respects. Meta II appearance kinetics in all of the preparations are best described by two and only two exponentials. The ratio of these two rates is always about 5. The fast fraction: slow fraction ratio depends upon temperature. These fractions are reversibly convertible in the dark, and are interconverted on a time-scale which is long compared to the meta II appearance rate. It is shown that the kinetics of the earlier step in the bleaching sequence, viz., lumi- meta I, is also described by double exponentials. Again the ratio of rates is ca. 5 and the fast-slow fractions correspond to those found in the meta I meta II step. It is proposed that these facts support an hypothesis for the existence of two conformeric states of rhodopsin which are in thermal equilibrium. Thermodynamic parameters associated with this proposed equilibrium are presented.     

Influence of Plant Hormones on Ethylene Production in Apple, Tomato, and Avocado Slices during Maturation and Senescence

Ethylene production by tissue slices from preclimacteric, climacteric, and postclimacteric apples was significantly reduced by isopentenyl adenosine (IPA), and by mixtures of IPA and indoleacetic acid, and of IPA, indoleacetic acid, and gibberellic acid after 4 hours of incubation. Ethylene production by apple (Pyrus malus L.) slices in abscisic acid was increased in preclimacteric tissues, decreased in climacteric peak tissues, and little affected in postclimacteric tissues. Indoleacetic acid suppressed ethylene production in tissues from preclimacteric apples but stimulated ethylene production in late climacteric rise, climacteric, and postclimacteric tissue slices. Gibberellic acid had less influence in suppressing ethylene production in preclimacteric peak tissue, and little influenced the production in late climacteric rise, climacteric peak, and postclimacteric tissues. IPA also suppressed ethylene production in pre- and postclimacteric tissue of tomatoes (Lycopersicon esculentum) and avocados (Persea gratissima). If ethylene production in tissue slices of ripening fruits is an index of aging, then IPA would appear to retard aging in ripening fruit, just as other cytokinins appear to retard aging in senescent leaf tissue.     

Preparation and antigenic properties of 5alpha-dihydrotestosterone-11-(O-carboxymethyl) oxime-BSA conjugate.

The C-11 (O-carboxymethyl) oxime derivative of 5-alphadihydrotestosterone (5alphaDHT) has been prepared. Due to steric hindrance at C-11, a novel two step procedure was used to introduce the (O-carboxymethyl) oxime at this position. Condensation of this oxime to bovine serum albumin afforded a conjugate which produced anti-5alphaDHT sera inoculated rabbits. Apart from a 30% cross reaction with testosterone, the antisera was reasonably specific for 5alphaDHT.     

Three-dimensional image of tubulin in zinc-induced sheets, reconstructed from electron micrographs

A three-dimensional image of zinc-induced brain tubulin sheets has been reconstructed by computer from digitized electron microscope images of negatively stained specimens. Different views of the sheets were obtained by tilting the specimens in the microscope and also by sectioning normal to the plane of the sheets. The overall resolution of the data is about 2 nm. The features of the resulting three-dimensional model suggest an explanation for the somewhat variable appearance of tubulin subunits in electron microscope images of negatively stained intact and opened-out microtubules.     

The activity patterns of Ommatoiulus moreletii (Diplopoda: Iulidae) in South Australia

Pitfall traps were set and visual observations made along regularly walked transects to assess the patterns of surface activity of Ommatoiulus moreletii in open grassland and dry sclerophyllous woodland in South Australia. Active O. moreletii were most commonly seen and trapped in autumn, to a lesser extent in spring, occasionally in summer and rarely in winter. Day to day variations in activity were related to changes in temperature and moisture. The activity of older stadia was greater than that of younger stadia.