Initiation events in in-vitro packaging of bacteriophage phi 29 DNA-gp3

Initiation events in the packaging of bacteriophage phi 29 DNA-gp3 (DNA-gene product 3 complex) were studied in a completely defined in-vitro system that included purified proheads, DNA-gp3 and the DNA packaging protein gp16. In the sequential interactions, gp16 first bound to, and was modified by, the prohead. The prohead-gp16 complex then bound to DNA-gp3, resulting in a second modification of gp16 that permitted binding of ATP. DNA-gp3 aggregates were produced, and the hydrolysis of ATP accompanied DNA-gp3 packaging. Binding and hydrolysis of ATP by gp16 was both prohead- and DNA-gp3-dependent. Interruption of packaging by DNase I addition revealed filled heads but few particles containing partial lengths of DNA, suggesting that following a rate-limiting initiation, the translocation of DNA-gp3 into the prohead was much faster in the defined in-vitro system than in extracts.     

Effects of growing conditions and development of the underlying exodermis on the vitality of the onion root epidermis

Bulbs of Allium cepa L., which had developed short, adventitious roots, were transferred to various conditions, i.e. vermiculite watered to saturation, vermiculite watered to half saturation, immersed in hydroculture, and immersed in hydroculture except for the proximal 20 mm which was continuously exposed to air. The development of the exodermis occurred in a patchy fashion in many roots but was not influenced by the growing conditions. The vitality of the epidermis declined under all conditions, the rate of decline being inversely related to the ambient moisture level. The differences between the treatments were most evident at the oldest region sampled (120 mm from the root tip) where 4% of the epidermal cells were dead in roots grown in hydroponics. This compared with 62% dead cells in saturated vermiculite, 78% in half-saturated vermiculite and 92% in roots exposed to air. Death of the epidermal cells was not accelerated by the maturation of the underlying exodermis. Epidermal cells which did not overlie a short cell of the exodermis (i.e. were only in contact with long cells) died earlier than the others: this trend was evident even prior to the maturation of the exodermis. These results suggest that the epidermal cells are not well connected symplasmically to the long cells or to the neighbouring epidermal cells. The large majority of epidermal cells (98% of the total) were in contact with a short cell of the exodermis. These epidermal cells tended to die off slowly, even under very favourable ambient conditions. Since these cells provide the major site for ion uptake in roots with a mature exodermis. their death may reduce the efficiency of the root for this activity.     

Encephalitozoon cuniculi: quantitation of parasites and evaluation of viability

Two methods (manual and automated) for quantitation of viable versus dead Encephalitozoon cuniculi are reported. The manual method uses ethidium bromide and acridine orange to stain dead and viable organisms, respectively. The stained organisms are visually differentiated with the aid of a fluorescence microscope. The automated method uses propidium iodide to stain dead parasites, which are differentiated from viable unstained parasites with the aid of a flow cytometer. An automated cell counter (Coulter Counter) was used to count rapidly large numbers of samples and to improve the sensitivity of counting low concentrations of parasites. These methods will enhance investigators' abilities to conduct quantitative experiments on host defense mechanisms against E. cuniculi.     

“Bicycles May Use Full Lane” Signage Communicates U.S. Roadway Rules and Increases Perception of Safety

Many global challenges, including obesity, health care costs, and climate change, could be addressed in part by increasing the use of bicycles for transportation. Concern about the safety of bicycling on roadways is frequently cited as a deterrent to increasing bicycle use in the USA. The use of effective signage along roadways might help alleviate these concerns by increasing knowledge about the rights and duties of bicyclists and motorists, ideally reducing crashes. We administered a web-based survey, using Twitter for recruitment, to examine how well three US traffic control devices communicated the message that bicyclists are permitted in the center of the travel lane and do not have to “get out of the way” to allow motorists to pass without changing lanes: “Bicycles May Use Full Lane” and “Share the Road” signage, and Shared Lane Markings on the pavement. Each was compared to an unsigned roadway. We also asked respondents whether it was safe for a bicyclist to occupy the center of the travel lane. “Bicycles May Use Full Lane” signage was the most consistently comprehended device for communicating the message that bicyclists may occupy the travel lane and also increased perceptions of safety. “Share the Road” signage did not increase comprehension or perceptions of safety. Shared Lane Markings fell somewhere between. “Bicycles May Use Full Lane” signage showed notable increases in comprehension among novice bicyclists and private motor vehicle commuters, critical target audiences for efforts to promote bicycling in the USA. Although limited in scope, our survey results are indicative and suggest that Departments of Transportation consider replacing “Share the Road” with “Bicycles May Use Full Lane” signage, possibly combined with Shared Lane Markings, if the intent is to increase awareness of roadway rights and responsibilities. Further evaluation through virtual reality simulations and on-road experiments is merited.     

Alive inside

This article provides an ethical analysis of the U.S. practice guideline update on disorders of consciousness. Our analysis focuses on the guideline’s recommendations regarding the use of investigational neuroimaging methods to assess brain-injured patients. Complex and multifaceted ethical issues have emerged because these methods alter the clinical understanding of consciousness. We address issues of false hope, patient suffering, and cost. We argue that, in spite of these concerns, there is significant benefit to using neuroimaging to assess brain-injured patients in most cases.     

Aquatic bird distributions in Mexico: designing conservation approaches quantitatively

The aquatic birds of Mexico include both a rich fauna of residents and a significant proportion of migratory species that breed in Canada and the United States, yet their distribution and richness patterns remain poorly known. We developed a detailed database of occurrences, and estimated distributions using niche modeling interpolations for 134 species associated with wetlands. Validations of the resulting maps indicated that the niche-modeling approach yields a useful picture of aquatic bird species distributions in the country. Richness patterns among aquatic birds differ from those for landbirds: species richness is concentrated in coastal areas, but endemism is focused in the Transvolcanic Belt and the Altiplano. Place prioritization exercises identified sets of areas that would maximize the protection of this diversity.     

Somatic Mutator activity expression is dependent on the strength of Cy trans-active signals in maize

Summary Two receptor element alleles (vp-rcy and bz-rcy) that respond to the trans-active element (Cy) controlling Mutator activity were used to analyze the strength of trans-active signals from Cy elements derived from a Mutator active line. Evidence is presented that the Mutator population tested consists mainly of a class of weak Cy elements designated as Cy:Mu. When Cy:Mu element are present in only a few copies, the strength of the combined transposition signal is weak. It is only when these active elements have a high copy number that the overall transposition signal is sufficiently strong enough to elicit a high frequency of transposition events. This study seeks to investigate the nature of the trans-active signal from Cy:Mu elements. The implication of these results for molecular studies is discussed.Journal Paper No. J-13083 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA, Project No. 2381