The In Vivo Kinetics of RNA Polymerase II Elongation during Co-Transcriptional Splicing

Kinetic analysis shows that RNA polymerase elongation kinetics are not modulated by co-transcriptional splicing and that post-transcriptional splicing can proceed at the site of transcription without the presence of the polymerase

Vertical Transmission of Listeria monocytogenes: Probing the Balance between Protection from Pathogens and Fetal Tolerance

Protection of the developing fetus from pathogens is one of the many critical roles of the placenta. Listeria monocytogenes is one of a select number of pathogens that can cross the placental barrier and cause significant harm to the fetus, leading to spontaneous abortion, stillbirth, preterm labor, and disseminated neonate infection despite antibiotic treatment. Such severe outcomes serve to highlight the importance of understanding how L. monocytogenes mediates infiltration of the placental barrier. Here, we review what is currently known regarding vertical transmission of L. monocytogenes as a result of cell culture and animal models of infection. In vitro cell culture and organ models have been useful for the identification of L. monocytogenes virulence factors that contribute to placental invasion. Examples include members of the Internalin family of bacterial surface proteins such as Interalin (Inl)A, InlB, and InlP that promote invasion of cells at the maternal-fetal interface. A number of animal models have been used to interrogate L. monocytogenes vertical transmission, including mice, guinea pigs, gerbils, and non-human primates; each of these models has advantages while still not providing a comprehensive understanding of L. monocytogenes invasion of the human placenta and/or fetus. These models do, however, allow for the molecular investigation of the balance between fetal tolerance and immune protection from L. monocytogenes during pregnancy

The Bacterial Surface Protein Internalin B Enhances Vertical Transmission of Listeria monocytogenes

Listeria monocytogenes is a facultative gram-positive intracellular bacterium that is capable of causing serious invasive infections in pregnant women resulting in abortion, still-birth, and disseminated fetal infection. Previously, a clinical L. monocytogenes isolate, 07PF0776, was identified as having an enhanced ability to target cardiac tissue; this tissue tropism appeared to result from amino acid variations within Internalin B (InlB), a bacterial surface protein associated with host cell invasion. Given that the mammalian receptor bound by InlB, Met, is abundantly expressed by placental tissue, we assessed 07PF0776 for its ability to be transmitted from mother to fetus. Pregnant Swiss-Webster mice were infected on gestational day E13 via tail vein injection with the standard isolate 10403S, a non-cardiotropic strain, or 07PF0776, the cardiac isolate. Pregnant mice infected with 07PF0776 exhibited significantly enhanced transmission of L. monocytogenes to placentas and fetuses compared to 10403S. Both bacterial burdens and the frequency of placental and fetal infection were increased in mice infected with the cardiac isolate. Strain 07PF0776 also exhibited an enhanced ability to invade Jar human trophoblast tissue culture cells in comparison to 10403S. 07PF0776 was found to have increased levels of InlB associated with the bacterial cell surface in comparison to 10403S. Overexpression of surface InlB via genetic modification was sufficient to confer enhanced invasion of the placenta and fetus for both 10403S and 07PF0776. 07PF0776 also exhibited more rapid invasion of the placenta compared to 10403S, with increased bacterial burdens and frequency of infection established as early as 48 hours post infection. 07PF0776 expressing inlB from 10403S (07PF0776 InlBNC) exhibited increased infection of the placenta and fetus compared to 10403S expressing inlB from 07PF0776 (10403S InlBC). It was found that 10403S InlBC did not retain InlB on the bacterial cell surface. These data support a critical role for surface InlB in the vertical transmission of L. monocytogenes

Vertical Transmission of Listeria monocytogenes: Probing the Balance between Protection from Pathogens and Fetal Tolerance

Protection of the developing fetus from pathogens is one of the many critical roles of the placenta. Listeria monocytogenes is one of a select number of pathogens that can cross the placental barrier and cause significant harm to the fetus, leading to spontaneous abortion, stillbirth, preterm labor, and disseminated neonate infection despite antibiotic treatment. Such severe outcomes serve to highlight the importance of understanding how L. monocytogenes mediates infiltration of the placental barrier. Here, we review what is currently known regarding vertical transmission of L. monocytogenes as a result of cell culture and animal models of infection. In vitro cell culture and organ models have been useful for the identification of L. monocytogenes virulence factors that contribute to placental invasion. Examples include members of the Internalin family of bacterial surface proteins such as Interalin (Inl)A, InlB, and InlP that promote invasion of cells at the maternal-fetal interface. A number of animal models have been used to interrogate L. monocytogenes vertical transmission, including mice, guinea pigs, gerbils, and non-human primates; each of these models has advantages while still not providing a comprehensive understanding of L. monocytogenes invasion of the human placenta and/or fetus. These models do, however, allow for the molecular investigation of the balance between fetal tolerance and immune protection from L. monocytogenes during pregnancy

The sleep and performance of train drivers during an extended freight-haul operation

The sleep and performance of train drivers was monitored across a 106-h rail operation between the Australian cities of Adelaide and Perth. The drivers worked alternating 8-h shift rotations across the operation and rested in specially equipped, crew-van carriages during non-work periods. The crew-van rest opportunities were associated with shorter bedtime spans, less total sleep time, and poorer sleep efficiency than sleeps initiated at home. The duration of crew-van sleeps was primarily dependent on the time of day at which the rest opportunities occurred. Overall, drivers incurred a significant cumulative sleep loss across the duration of the operation. Despite the deficit, drivers were able to sustain vigilance performance across the operation

The driver vigilance telemetric control system (DVTCS): investigating sensitivity to experimentally induced sleep loss and fatigue

Vigilance technologies are used in the Australian rail industry to address the risks associated with driver sleepiness and fatigue. The aim of this study was to investigate whether a new device, designed to detect lowered states of arousal using electrodermal activity (EDA), would be sensitive to experimentally induced sleepiness and fatigue. Fifteen individuals (7 of them female, 9 male; 18–32 years of age) spent 3 consecutive days in the laboratory, which included 1 night of sustained wakefulness (28 h). The participants completed a 10-min psychomotor vigilance task (PVT) and fatigue and sleepiness ratings every 2 h, and a 30-min driving simulator every 4 h. As was expected, simulated driving, PVT, and subjective ratings indicated increasing levels of sleepiness and fatigue during sustained wakefulness. The EDA device output did not coincide with these findings. The results indicated that the EDA indicator was not sensitive to increased sleepiness and fatigue at the levels produced in the present study

Impact of layover length on sleep, subjective fatigue levels, and sustained attention of long-haul airline pilots

Long-haul airline pilots often experience elevated levels of fatigue due to extended work hours and circadian misalignment of sleep and wake periods. During long-haul trips, pilots are typically given 1–3 d off between flights (i.e., layover) to recover from, and prepare for, duty. Anecdotally, some pilots prefer long layovers because it maximizes the time available for recovery and preparation, but others prefer short layovers because it minimizes both the length of the trip, and the degree to which the body clock changes from “home time” to the layover time zone. The aim of this study was to examine the impact of layover length on the sleep, subjective fatigue levels, and capacity to sustain attention of long-haul pilots. Participants were 19 male pilots (10 Captains, 9 First Officers) working for an international airline. Data were collected during an 11- or 12-d international trip. The trips involved (i) 4 d at home prior to the trip; (ii) an eastward flight of 13.5 h across seven time zones; (iii) a layover of either 39 h (i.e., short, n = 9) or 62 h (i.e., long, n = 10); (iv) a return westward flight of 14.3 h across seven time zones; and (v) 4 d off at home after the trip. Sleep was recorded using a self-report sleep diary and wrist activity monitor; subjective fatigue level was measured using the Samn-Perelli Fatigue Checklist; and sustained attention was assessed using the psychomotor vigilance task for a personal digital assistant (PalmPVT). Mixed-model regression analyses were used to determine the effects of layover length (short, long) on the amount of sleep that pilots obtained during the trip, and on the pilots' subjective fatigue levels and capacity to sustain attention. There was no main effect of layover length on ground-based sleep or in-flight sleep, but pilots who had a short layover at the midpoint of their trip had higher subjective fatigue levels and poorer sustained attention than pilots who had a long layover. The results of this study indicate that a short layover during a long-haul trip does not substantially disrupt pilots' sleep, but it may result in elevated levels of fatigue during and after the trip. If short layovers are used, pilots should have a minimum of 4 d off to recover prior to their next long-haul trip