Initiation of bacteriophage T4 DNA replication and replication fork dynamics: a review in the Virology Journal series on bacteriophage T4 and its relatives

Abstract Bacteriophage T4 initiates DNA replication from specialized structures that form in its genome. Immediately after infection, RNA-DNA hybrids (R-loops) occur on (at least some) replication origins, with the annealed RNA serving as a primer for leading-strand synthesis in one direction. As the infection progresses, replication initiation becomes dependent on recombination proteins in a process called recombination-dependent replication (RDR). RDR occurs when the replication machinery is assembled onto D-loop recombination intermediates, and in this case, the invading 3' DNA end is used as a primer for leading strand synthesis. Over the last 15 years, these two modes of T4 DNA replication initiation have been studied in vivo using a variety of approaches, including replication of plasmids with segments of the T4 genome, analysis of replication intermediates by two-dimensional gel electrophoresis, and genomic approaches that measure DNA copy number as the infection progresses. In addition, biochemical approaches have reconstituted replication from origin R-loop structures and have clarified some detailed roles of both replication and recombination proteins in the process of RDR and related pathways. We will also discuss the parallels between T4 DNA replication modes and similar events in cellular and eukaryotic organelle DNA replication, and close with some current questions of interest concerning the mechanisms of replication, recombination and repair in phage T4.</p

Aircraft Cabin Turbulence Warning Experiment

New turbulence prediction technology offers the potential for advance warning of impending turbulence encounters, thereby allowing necessary cabin preparation time prior to the encounter. The amount of time required for passengers and flight attendants to be securely seated (that is, seated with seat belts fastened) currently is not known. To determine secured seating-based warning times, a consortium of aircraft safety organizations have conducted an experiment involving a series of timed secured seating trials. This demonstrative experiment, conducted on October 1, 2, and 3, 2002, used a full-scale B-747 wide-body aircraft simulator, human passenger subjects, and supporting staff from six airlines. Active line-qualified flight attendants from three airlines participated in the trials. Definitive results have been obtained to provide secured seating-based warning times for the developers of turbulence warning technolog

A Comparison of Six Maternal Genetic Lines for Sow Longevity

Data from the National Pork Producers Council Maternal Line National Genetic Evaluation Program were used to compare the sow longevity of six different genetic lines, and to estimate the associations of gilt backfat thickness, age at first farrowing, litter size at first farrowing, litter weight at first farrowing, average feed intake during lactation, and average backfat loss during lactation with sow longevity. The lines evaluated were American Diamond Genetics, Danbred North America, Dekalb-Monsanto DK44, Dekalb-Monsanto GPK347, Newsham Hybrids, and National Swine Registry. The results suggest that the sows of Dekalb-Monsanto GPK347 had a clearly lower risk of being culled than the sows of other five lines. Moreover, the shape of the survival distribution function of Delkab- Monsanto GPK347 is clearly different than the other five lines. There were high culling rates due to reproductive failure after first weaning in the sows of the five other lines, however this increased culling rate did not exist in the Dekalb-Monsanto GPK347 line. The results further suggest that sows with lower feed intake and greaterer backfat loss during lactation had the shorter productive lifetime. These between line differences indicate that it is possible to select for sow longevity. More research is needed to show the most efficient methods to select for sow longevity

The effects of sediment disturbance on the macrobenthos of the St. Lucia Narrows, Natal.

Thesis (M.Sc.)-University of Natal, Durban, 1992.Estuarine studies worldwide have shown that sediment disturbance effects on the macrobenthos are reIated to the nature and scale of the disturbance. Decreased species densities, diversity and richness have been found where the substratum and current patterns have been altered either by direct removal or by the creation of channels . Sediment disturbance in the St. Lucia Narrows has occurred through dredging, beam trawling and episodic floods. The Narrows, a meandering tidal channel approximately 21 km long linking the st Lucia Lakes to the sea, were dredged between 1952 and 1971 to provide a greater flow of seawater to the lakes during periods of low lake levels. A canal was cut through land from the Mfolosi River to the Narrows in an attempt to ameliorate hypersaline conditions in the Lakes, but was never commissioned. Beam trawling has formed the basis of a prawn bait fishery since the 1930's. The bait boats trawl on the mudflats over the entire Narrows on a daily basis and often churn the substratum with their propellers. The objectives of this study were to determine the effects of dredging, a once-off large scale disturbance, and beam trawling, a frequent small scale disturbance, on the macrobenthos of the Narrows. Studies in 1983 and 1984 showed that the dredged channel was impoverished compared with the adjacent mudflat, and that the Link Canal was devoid of benthos. In 1988 species densities, especially of polychaetes, were found to be lower in areas open to beam trawling than in adjacent closed areas. The dredged channel during the present study was again impoverished compared with the adjacent mudflats. The three most abundant species occurring on the mudflats, the crab Tylodiplax blephariskios, the amphipod Victoriopsia chilkensis and capitellid polychaetes, were recorded at densities an order of magnitude lower in the channel than on the mudflats. The substratum in the channel was generally sandier than the mudflats, and this condition appeared to be maintained by the scouring action of tidal currents. It was calculated that the creation of the dredged channel had reduced the standing benthic biomass in the Narrows by a minimum of approximately 20%. The Link Canal was colonised by the three major mud flat species , but at densities an order of magnitude lower than the mudflats. Beam trawling of experimental sites at monthly and 6-monthly intervals on muddy and sandy substrata in the Narrows between July 1989 and July 1990 did not appear to have a negative effect on the benthos. The coverage of the bait boats was calculated to be comparable to the trawling effort in this study, and suggested that the bait fishery is not having a detrimental effect on the benthos. It was concluded that the macrobenthos in the Narrows represented a pioneering community characteristic of estuaries, either not affected by, or able to recover from small scale and episodic disturbances provided that there was no long term habitat modification

Electroconvulsive Therapy: A Review of Its Current Status

This article presents an overview of the current knowledge and practice of ECT. It provides a brief history of the development of ECT followed by a discussion of the accepted indications for ECT in psychiatric practice, including major depression, bipolar disorder (mania and depression), and schizophrenia. Moreover, a description of the technique of performing ECT is given. Also examined are the use of ECT in medically ill patients and the risks associated with ECT. In conclusion, with the aid of advances in anesthesia and the delivery of ECT, electroconvulsive therapy is a safe and effective treatment of mood and psychotic disorders that have been resistant to other treatment modalities

The Impact of Poor Health Behaviors on Workforce Disability

The effects of poor health habits on mortality have been studied extensively. However, few studies have examined the impact of these health behaviors on workforce disability. In the Health and Retirement Study, a nationally representative cohort of 6044 Americans who were between the ages of 51 and 61 and who were working in 1992, we found that both baseline smoking status and a sedentary lifestyle predict workforce disability six years later. If this relationship is causal, cost-benefit analyses of health behavior intervention that neglect workforce disability may substantially underestimate the benefits of such interventions.

Factors Associated with Sow Stayability

The purpose of this study was to determine the association of production factors with stayability to parity 4 (STAY 4), defined as the ability of a sow to reach 4th parity. Data was from the National Pork Producers Council Maternal Line National Genetic Evaluation Program, which included 6 genetic lines and consisted of 3,283 female pigs. Factors significant for STAY 4 included: farm, entry date, age at first farrowing, average daily gain, gilt backfat, and lactation prior to removal, feed intake, number born alive, and lactation length. Age at first farrowing and lactation feed intake in the lactation prior to removal had the greatest phenotypic relationships with sow longevity across genetic lines. A younger age at first farrowing under a uniform environment was positively related to length of productive life. Genetically, selection for a reduced age at first farrowing should increase sow longevity. However, a sow that is older at first farrowing may also be favorable for sow longevity. Commercial producers should strive to increase lactation feed intake through good management to ensure sow longevity

Relationship of Pork Longissimus Muscle Fatty Acid Profile with Pork Loin Texture and Sensory Traits

The objective this project was to determine the contribution of lipid composition and lipid profile to textural and sensory properties of fresh pork. Loins from pigs (n=2009; from 306 sires and 1030 dams) were used to determine the contribution of lipid composition and lipid profile to textural and sensory properties of fresh pork. Total lipid content was correlated with saturated fatty acids and negatively correlated with unsaturated fatty acids. Myristic acid was positively correlated with tenderness and negatively correlated with star probe. Negative correlations between stearic acid and the traits of tenderness and juiciness were detected. No other fatty acid component was determined to have a strong correlation with pork texture or sensory traits. The results suggest that when pigs are fed a similar diet, normal variations in pork loin fatty acid profile do not contribute to differences in pork texture and sensory traits