Replication of Coliphage M-13 I. Effects on Host Cells After Synchronized Infection

Techniques have been described for synchronization of bacteriophage M-13 infection of host cells. The latent period in infected cells was 10 min, and no appreciable number of intracellular phage was observed. Phage production proceeded in three phases after release of the starvation block: an initial rapid exponential rate of progeny phage release without cell lysis, a period of rate transition accompanying the resumption of host cell division, and a second, slower exponential rate of phage production which paralleled the rate of host cell division. The size of infected cells was not affected by infection, but the generation time was increased by 25%. Starved infected cells exhibited a much longer lag in attaining an exponential rate of growth upon the addition of nutrients than did an uninfected control culture.     

Inter and intra‐population phenotypic and genotypic structuring in the European whitefish Coregonus lavaretus,a rare freshwater fish in Scotland

This study revealed between‐lake genetic structuring between Coregonus lavaretus collected from the only two native populations of this species in Scotland, U.K. (Lochs Eck and Lomond) evidenced by the existence of private alleles (12 in Lomond and four in Eck) and significant genetic differentiation (F_ST = 0·056) across 10 microsatellite markers. Juvenile C. lavaretus originating from eggs collected from the two lakes and reared in a common‐garden experiment showed clear phenotypic differences in trophic morphology (i.e. head and body shape) between these populations indicating that these characteristics were, at least partly, inherited. Microsatellite analysis of adults collected from different geographic regions within Loch Lomond revealed detectable and statistically significant but relatively weak genetic structuring (F_ST = 0·001–0·024) and evidence of private alleles related to the basin structure of the lake. Within‐lake genetic divergence patterns suggest three possibilities for this observed pattern: (1) differential selection pressures causing divergence into separate gene pools, (2) a collapse of two formerly divergent gene pools and (3) a stable state maintained by balancing selection forces resulting from spatial variation in selection and lake heterogeneity. Small estimates of effective population sizes for the populations in both lakes suggest that the capacity of both populations to adapt to future environmental change may be limited.     

Bioremediation Assessment of Hydrocarbon-Contaminated Soils from the High Arctic

The bioremediation potential of hydrocarbon-contaminated soils from the most northerly inhabited station in the world, Canadian Forces Station - Alert, was assessed. Microbial enumeration, by both viable plate counts and direct counts, combined with molecular analysis (polymerase chain reaction and colony hybridization) for hydrocarbon catabolic genes (alkB, ndoB, xylE), demonstrated the presence of significant numbers of cold-adapted hydrocarbon-degrading microorganisms. The degradative activity of these populations was assessed by mineralization of ¹⁴Clabeled hexadecane (C16) at 5°C in untreated and treated soils. Although very low rates of C16 mineralization were observed in the untreated soils, nutrient supplementation with a fertilizer markedly increased C16 mineralization. Highly active cold-adapted hydrocarbon-degrading consortia were prepared from soil slurries, and their degradative potentials were monitored by biomass measurements and mineralization activity. Bio augmentation of the contaminated soils with consortia containing the greatest percentages of degradative bacteria resulted in the shortest C16 mineralization acclimation period. However, treatment with the consortia plus fertilizer did not appreciably increase C16 mineralization or reduce total petroleum hydrocarbon concentrations to a greater extent than did the fertilizer treatment alone. These results indicate that the soils possessed sufficient numbers of cold-adapted degradative bacteria, and that fertilizer application alone was sufficient to obtain elevated levels of degradative activity at low ambient summer temperatures.     

A 0.5 G, 60 Hz magnetic field suppresses melatonin production in pinealocytes

The objective of this study was to develop a model for testing various hypotheses concerning possible mechanisms whereby electromagnetic fields might induce suppression of nighttime melatonin production in rodents. A published method for digesting freshly obtained pineal glands to the single cell level was modified, yielding better than 95% viability. An in vitro exposure facility developed for the Food and Drug Administration was used for 12-h overnight exposures of primary pinealocyte cultures to 0.05 mT, 60 Hz, vertical AC and 0.06 μT, DC fields. After exposure, cells were separated from the supernatant by centrifugation. Supernatant melatonin was measured by ELISA assays. Data from 10 experiments demonstrated an average 46% reduction in norepinephrine-induced production of melatonin in the pinealocytes. The results support the hypothesis that EM exposure can produce pineal gland melatonin suppression by affecting individual cells. Bioelectromagnetics 19:123–127, 1998. Published 1998 Wiley-Liss, Inc.     

Intracellular calcium signaling by jurkat T-lymphocytes exposed to a 60 hz magnetic field

To explore possible biochemical mechanisms whereby electromagnetic fields of around 0.1 mT might affect immune cells or developing cancer cells, we studied intracellular calcium signaling in the model system Jurkat E6-1 human T-leukemia cells during and following exposure to a 60 Hz magnetic field. Cells were labeled with the intracellular calcium-sensitive fluorescent dye Fluo-3, stimulated with a monoclonal antibody against the cell surface structure CD3 (associated with ligand-stimulated T-cell activation), and analyzed on a FACScan flow-cytometer for increases in intensity of emissions in the range of 515–545 nm. Cells were exposed during or before calcium signal-stimulation to 0.15 mT_rms 60 Hz magnetic field. The total DC magnetic field of 78.2 μT was aligned 17.5° off the vertical axis. Experiments used both cells cultured at optimal conditions at 37 °C and cells grown under suboptimal conditions of 24 °C, lowered external calcium, or lowered anti-CD3 concentration. These experiments demonstrate that intracellular signaling in Jurkat E6-1 was not affected by a 60 Hz magnetic field when culture and calcium signal-stimulation were optimal or suboptimal. These results do not exclude field-induced calcium-related effects further down the calcium signaling pathway, such as on calmodulin or other calcium-sensitive enzymes. Bioelectromagnetics 18:439–445, 1997. © 1997 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Presenilin-1 280Glu-->Ala mutation alters C-terminal APP processing yielding longer abeta peptides: implications for Alzheimer's disease

Presenilin (PS) mutations enhance the production of the Abeta42 peptide that is derived from the amyloid precursor protein (APP). The pathway(s) by which the Abeta42 species is preferentially produced has not been elucidated, nor is the mechanism by which PS mutations produce early-onset dementia established. Using a combination of histological, immunohistochemical, biochemical, and mass spectrometric methods, we examined the structural and morphological nature of the amyloid species produced in a patient expressing the PS1 280Glu-->Ala familial Alzheimer's disease mutation. Abundant diffuse plaques were observed that exhibited a staining pattern and morphology distinct from previously described PS cases, as well as discreet amyloid plaques within the white matter. In addition to finding increased amounts of CT99 and Abeta42 peptides, our investigation revealed the presence of a complex array of Abeta peptides substantially longer than 42/43 amino acid residue species. The increased hydrophobic nature of longer Abeta species retained within the membrane walls could impact the structure and function of plasma membrane and organelles. These C-terminally longer peptides may, through steric effects, dampen the rate of turnover by critical amyloid degrading enzymes such as neprilysin and insulin degrading enzyme. A complete understanding of the deleterious side effects of membrane bound Abeta as a consequence of gamma-secretase alterations is needed to understand Alzheimer's disease pathophysiology and will aid in the design of therapeutic interventions.