Identification and characterization of genes encoding sex pheromone cAM373 activity in Enterococcus faecalis and Staphylococcus aureus

The sex pheromone cAM373 of Enterococcus faecalis and the related staph -cAM373 of Staphylococcus aureus were found to correspond to heptapeptides located within the C-termini of the signal sequences of putative prelipoproteins. The deduced mature forms of the lipoproteins share no detectable homology and presumably serve unrelated functions in the cells. The chromosomally encoded genetic determinants for production of the pheromones have been identified and designated camE (encoding cAM373) and camS (encoding staph -cAM373). Truncated and full-length clones of camE were generated in Escherichia coli , in which cAM373 activity was expressed. In E. faecalis , insertional inactivation in the middle of camE had no detectable phenotypic effects on the pheromone system. Establishment of an in frame translation stop codon within the signal sequence resulted in reduction of cAM373 activity to 3% of normal levels. The camS determinant has homologues in Staphylococcus epidermidis , Bacillus subtilis and Listeria monocytogenes ; however, corresponding heptapeptides present within those sequences do not resemble staph -cAM373 closely. The particular significance of staph -cAM373 as a potential intergeneric inducer of transfer-proficient genetic elements is discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75605/1/j.1365-2958.2002.02922.x.pd

Driver Behavior as a Function of Ambient Light and Road Geometry

OBJECTIVES To determine how ambient light (day versus night) and road geometry affect driving behavior,especially the speeds that drivers choose when not constrained by lead vehicles.METHODSRecently, it has become technically easier to observe how people drive b offering them longtermuse of highly instrumented vehicles. Much of this type of work has been done in connectionwith large-scale field operational tests (FOTs) of various innovative vehicle systems. Theinformation obtained is in many ways complementary to information from observation of traffic.Traffic observation often provides information about a large number of drivers, but at a relativelycoarse level and in a spatially and temporally limited context (i.e., observing how a large numberof drivers negotiate a particular intersection). In contrast, long-term use of highly instrumentedvehicles is more restricted in terms of how many drivers can be observed, although the feasiblenumbers are now reasonably high. On the positive side, data from instrumented vehicles canoffer very detailed information about driving behavior over many miles and many days.In this paper, we present results from a database of driving behavior that was derived from arecent FOT for an adaptive cruise control (ACC) system (although the data used here are all fromphases of the study that involved only normal vehicle equipment). The FOT involved tenidentical cars that were instrumented for a variety of types of data. The most important data forpresent purposes were: speed, yaw rate, location from the Global Positioning System (GPS), andpresence or absence of a lead vehicle within about 100 m based on the forward-looking sensorsof the ACC system. The instrumented cars were driven by a total of 108 participants, each ofwhom was given a car to use as his or her own vehicle in normal driving for either two or fiveweeks. The participants were sampled from licensed drivers in southeastern Michigan, andrepresented a wide range of age and driving experience.RESULTSResults will be reported in terms of speed as a function of horizontal road curvature in light anddark conditions, and as a function of driver age and gender, all for situations in which there is nolead vehicle within about 100 m. CONCLUSIONSCurrent evidence about headlighting suggests that drivers’ ability to see and negotiate theroadway is virtually unaffected by differences in ambient light, although their ability to perceiveand avoid objects on the road, such as pedestrians, is greatly reduced when headlamps are themain source of light. There is also evidence that drivers do not markedly reduce their speed inconditions of low ambient light. The current analysis allows us to determine how drivers react tospecific road geometries in light and dark conditions. This has implications for how well drivers’perceptual abilities match their driving behavior, and also for assessing the potential benefit of avariety of innovative headlighting systems that are currently being designed to adapt in variousways to vehicle speed and road geometry

Driver Behavior as a Function of Ambient Light and Road Geometry

OBJECTIVES To determine how ambient light (day versus night) and road geometry affect driving behavior,especially the speeds that drivers choose when not constrained by lead vehicles.METHODSRecently, it has become technically easier to observe how people drive b offering them longtermuse of highly instrumented vehicles. Much of this type of work has been done in connectionwith large-scale field operational tests (FOTs) of various innovative vehicle systems. Theinformation obtained is in many ways complementary to information from observation of traffic.Traffic observation often provides information about a large number of drivers, but at a relativelycoarse level and in a spatially and temporally limited context (i.e., observing how a large numberof drivers negotiate a particular intersection). In contrast, long-term use of highly instrumentedvehicles is more restricted in terms of how many drivers can be observed, although the feasiblenumbers are now reasonably high. On the positive side, data from instrumented vehicles canoffer very detailed information about driving behavior over many miles and many days.In this paper, we present results from a database of driving behavior that was derived from arecent FOT for an adaptive cruise control (ACC) system (although the data used here are all fromphases of the study that involved only normal vehicle equipment). The FOT involved tenidentical cars that were instrumented for a variety of types of data. The most important data forpresent purposes were: speed, yaw rate, location from the Global Positioning System (GPS), andpresence or absence of a lead vehicle within about 100 m based on the forward-looking sensorsof the ACC system. The instrumented cars were driven by a total of 108 participants, each ofwhom was given a car to use as his or her own vehicle in normal driving for either two or fiveweeks. The participants were sampled from licensed drivers in southeastern Michigan, andrepresented a wide range of age and driving experience.RESULTSResults will be reported in terms of speed as a function of horizontal road curvature in light anddark conditions, and as a function of driver age and gender, all for situations in which there is nolead vehicle within about 100 m. CONCLUSIONSCurrent evidence about headlighting suggests that drivers’ ability to see and negotiate theroadway is virtually unaffected by differences in ambient light, although their ability to perceiveand avoid objects on the road, such as pedestrians, is greatly reduced when headlamps are themain source of light. There is also evidence that drivers do not markedly reduce their speed inconditions of low ambient light. The current analysis allows us to determine how drivers react tospecific road geometries in light and dark conditions. This has implications for how well drivers’perceptual abilities match their driving behavior, and also for assessing the potential benefit of avariety of innovative headlighting systems that are currently being designed to adapt in variousways to vehicle speed and road geometry

A Fluorescence Based-Proliferation Assay for the Identification of Replicating Bacteria Within Host Cells

Understanding host pathogen interactions is paramount to the development of novel antimicrobials. An important facet of this pursuit is the accurate characterization of pathogen replication within infected host cells. Here we describe the use of a fluorescence-based proliferation assay to identify intracellular populations of replicating bacteria at the subcellular level. Using Staphylococcus aureus as a model Gram-positive bacterial pathogen and macrophages as a model host phagocyte, we demonstrate this assay can be used to reliably identify individual phagocytes that contain replicating bacteria. Furthermore, we demonstrate this assay is compatible with additional cellular probes that enable characterization of cellular compartments in which replicating bacteria reside. Finally, we demonstrate that this assay facilitates the investigation of both Gram-negative and Gram-positive bacteria within host cells

Dynamic macrophage “probing” is required for the efficient capture of phagocytic targets

Rather than passively binding ligands via immunoreceptors, macrophages capture particles by repeated extension of actin-rich protrusions

Enterococcal sex pheromone precursors are part of signal sequences for surface lipoproteins

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73811/1/j.1365-2958.2000.01687.x.pd

Enterococcal sex pheromone precursors are part of signal sequences for surface lipoproteins

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73811/1/j.1365-2958.2000.01687.x.pd

The yeast molecular chaperone, Hsp104, influences transthyretin aggregate formation

Patients with the fatal disorder Transthyretin Amyloidosis (ATTR) experience polyneuropathy through the progressive destruction of peripheral nervous tissue. In these patients, the transthyretin (TTR) protein dissociates from its functional tetrameric structure, misfolds, and aggregates into extracellular amyloid deposits that are associated with disease progression. These aggregates form large fibrillar structures as well as shorter oligomeric aggregates that are suspected to be cytotoxic. Several studies have shown that these extracellular TTR aggregates enter the cell and accumulate intracellularly, which is associated with increased proteostasis response. However, there are limited experimental models to study how proteostasis influences internalized TTR aggregates. Here, we use a humanized yeast system to recapitulate intracellular TTR aggregating protein in vivo. The yeast molecular chaperone Hsp104 is a disaggregase that has been shown to fragment amyloidogenic aggregates associated with certain yeast prions and reduce protein aggregation associated with human neurogenerative diseases. In yeast, we found that TTR forms both SDS-resistant oligomers and SDS-sensitive large molecular weight complexes. In actively dividing cultures, Hsp104 has no impact on oligomeric or large aggregate populations, yet overexpression of Hsp104 is loosely associated with an increase in overall aggregate size. Interestingly, a potentiating mutation in the middle domain of Hsp104 consistently results in an increase in overall TTR aggregate size. These data suggest a novel approach to aggregate management, where the Hsp104 variant shifts aggregate populations away from toxic oligomeric species to more inert larger aggregates. In aged cultures Hsp104 overexpression has no impact on TTR aggregation profiles suggesting that these chaperone approaches to shift aggregate populations are not effective with age, possibly due to proteostasis decline

The influence of sun loading on the visibility of clear-lens turn signals

There is some concern that turn signal lamps with clear outer lenses make it difficult in bright, sunny conditions to decide whether the signal is on or not. Two studies were performed. The first study was a survey of current practice in the U.S. with regard to the use of clear-lens turn signal lamps. The main results are that clear outer lenses on rear turn signal lamps are used in about 28% of all vehicle models, while the corresponding percentage for front turn signal lamps is about 70%. The second study photometrically evaluated, under bright, sunny conditions, both luminance contrast and color contrast between the on and off states for turn signal lamps that use either an amber lens or a clear lens. The results indicate that luminance contrast between the on and off states is greater for lamps using an amber lens. On the other hand, the results indicate that color contrast between the on and off states is greater for lamps using a clear lens. Because luminance contrast is likely to be the primary variable influencing driver performance, these results suggest that using clear-lens turn signal lamps is likely to make it more difficult to determine, in bright, sunny conditions, whether the signal is on or not. However, the magnitude of the decrement in real-world performance with clear-lens signal lamps remains to be ascertained.Michigan University, Ann Arbor, Industry Affiliation Program for Human Factors in Transportation Safetyhttp://deepblue.lib.umich.edu/bitstream/2027.42/49364/1/UMTRI-98-2.pd

Trapped Surfaces in Vacuum Spacetimes

An earlier construction by the authors of sequences of globally regular, asymptotically flat initial data for the Einstein vacuum equations containing trapped surfaces for large values of the parameter is extended, from the time symmetric case considered previously, to the case of maximal slices. The resulting theorem shows rigorously that there exists a large class of initial configurations for non-time symmetric pure gravitational waves satisfying the assumptions of the Penrose singularity theorem and so must have a singularity to the future.Comment: 14 page