Specific Times Of Day Research Articles

Endogenous Circadian Rhythm in Vasovagal Response to Head-Up Tilt

The incidence of syncope exhibits a daily pattern with more occurrences in the morning, possibly as a result of influences from the endogenous circadian system and/or the daily pattern of behavioral/emotional stimuli. This study tested the hypothesis that the circadian system modulates cardiovascular responses to postural stress, leading to increased susceptibility to syncope at specific times of day. Twelve subjects underwent a 13-day in-laboratory protocol in which subjects' sleep-wake cycles were adjusted to 20 hours for 12 cycles. A 15-minute tilt-table test (60° head-up) was performed ≈4.5 hours after scheduled awakening in each cycle so that 12 tests in each subject were distributed evenly across the circadian cycle. Of 144 tests, signs/symptoms of presyncope were observed in 21 tests in 6 subjects. These presyncope events displayed a clear circadian rhythm (P=0.028) with almost all cases (17/21) occurring in the half of the circadian cycle corresponding to the biological night (10:30 pm to 10:30 am). Significant circadian rhythms were also observed in hemodynamic and autonomic function markers (blood pressure, heart rate, epinephrine, norepinephrine, and indices of cardiac vagal tone) that may underlie the circadian rhythm of presyncope susceptibility. The circadian system affects cardiovascular responses to postural stress, resulting in greater susceptibility to presyncope during the night. This finding suggests that night-shift workers and people with disrupted sleep at night may have greater risk of syncope as a result of their exposure to postural stress during the biological night.

Network Quantitative Trait Loci Mapping of Circadian Clock Outputs Identifies Metabolic Pathway-to-Clock Linkages in Arabidopsis

Modern systems biology permits the study of complex networks, such as circadian clocks, and the use of complex methodologies, such as quantitative genetics. However, it is difficult to combine these approaches due to factorial expansion in experiments when networks are examined using complex methods. We developed a genomic quantitative genetic approach to overcome this problem, allowing us to examine the function(s) of the plant circadian clock in different populations derived from natural accessions. Using existing microarray data, we defined 24 circadian time phase groups (i.e., groups of genes with peak phases of expression at particular times of day). These groups were used to examine natural variation in circadian clock function using existing single time point microarray experiments from a recombinant inbred line population. We identified naturally variable loci that altered circadian clock outputs and linked these circadian quantitative trait loci to preexisting metabolomics quantitative trait loci, thereby identifying possible links between clock function and metabolism. Using single-gene isogenic lines, we found that circadian clock output was altered by natural variation in Arabidopsis thaliana secondary metabolism. Specifically, genetic manipulation of a secondary metabolic enzyme led to altered free-running rhythms. This represents a unique and valuable approach to the study of complex networks using quantitative genetics.

Melatonin and IP3-induced Ca2+ Release from Intracellular Stores in the Malaria Parasite Plasmodium falciparum within Infected Red Blood Cells

IP(3)-dependent Ca(2+) signaling controls a myriad of cellular processes in higher eukaryotes and similar signaling pathways are evolutionarily conserved in Plasmodium, the intracellular parasite that causes malaria. We have reported that isolated, permeabilized Plasmodium chabaudi, releases Ca(2+) upon addition of exogenous IP(3). In the present study, we investigated whether the IP(3) signaling pathway operates in intact Plasmodium falciparum, the major disease-causing human malaria parasite. P. falciparum-infected red blood cells (RBCs) in the trophozoite stage were simultaneously loaded with the Ca(2+) indicator Fluo-4/AM and caged-IP(3). Photolytic release of IP(3) elicited a transient Ca(2+) increase in the cytosol of the intact parasite within the RBC. The intracellular Ca(2+) pools of the parasite were selectively discharged, using thapsigargin to deplete endoplasmic reticulum (ER) Ca(2+) and the antimalarial chloroquine to deplete Ca(2+) from acidocalcisomes. These data show that the ER is the major IP(3)-sensitive Ca(2+) store. Previous work has shown that the human host hormone melatonin regulates P. falciparum cell cycle via a Ca(2+)-dependent pathway. In the present study, we demonstrate that melatonin increases inositol-polyphosphate production in intact intraerythrocytic parasite. Moreover, the Ca(2+) responses to melatonin and uncaging of IP(3) were mutually exclusive in infected RBCs. Taken together these data provide evidence that melatonin activates PLC to generate IP(3) and open ER-localized IP(3)-sensitive Ca(2+) channels in P. falciparum. This receptor signaling pathway is likely to be involved in the regulation and synchronization of parasite cell cycle progression.

Evening circadian oscillator as the primary determinant of rhythmic motivation for Drosophila courtship behavior

Circadian clocks of Drosophila melanogaster motivate males to court females at a specific time of day. However, clock neurons involved in courtship rhythms in the brain of Drosophila remain totally unknown. The circadian locomotor behavior of Drosophila is controlled by morning (M cells) and evening (E cells) cells in the brain, which regulate morning and evening activities, respectively. Here, we identified the brain clock neurons that are responsible for the circadian rhythms of the close-proximity (CP) behavior that reflects male courtship motivation. Interestingly, the ablation or functional molecular clock disruption of E cells caused arrhythmic CP behavior, but that of M cells resulted in sustained CP rhythms even in constant darkness. In addition, the ablation of some dorsal lateral neurons (LNd) of E cells using neuropeptide-F (NPF)-GAL4 did not impair CP rhythms. These findings suggested that the NPF-negative LNds and DN1s of E cells include cells essential for circadian CP behavior in Drosophila.

Long‐term change in thermospheric temperature above Saint Santin

The 1966–1987 Saint Santin/Nançay incoherent scatter radar database is analyzed to determine long‐term trends beyond those associated with the “natural” variations of solar and magnetic activity, season, and time of day. Trends averaging some −3 K/yr are found in the F region. Positive trends in the E region may be explained by the subsidence of an overlying warmer regime of air. The trend line seems to change slope around the “breakpoint” year 1979, with the cooling changing from −0.8 K/yr before that time to −5.5 K/yr afterward at 350 km altitude. These trends greatly exceed those predicted by model simulations for increases in greenhouse gas concentrations. Further, carbon dioxide shows no such breakpoint year, but ozone does, near the time of the change in thermospheric trend, and a surface climatic regime shift has also been reported near this time. It is not clear that greenhouse gases are driving the long‐term trend in thermospheric temperature. Restriction of analysis to a particular time of day results in greatly different trends, from near zero at midnight to −6 K/yr at noon at 350 km altitude. A separate analysis to determine the long‐term trend in the amplitude of the 24 h tide at 350 km altitude shows a large change, with the amplitude diminishing from 136 K in 1966 to 89 K in 1988. Our results show the great need to remove all other natural variations from long‐term data sets in determining long‐term trends to avoid great ambiguity in trend interpretation.

Disconnected circadian and cell cycles in a tumor-driven cell line

Cell division occurs at a specific time of day in numerous species, suggesting that the circadian and cell cycles are coupled in vivo. By measuring the cell cycle rhythm in real-time, we recently showed that the circadian and cell cycles are not coupled in immortalized fibroblasts, resulting in a rapid rate of cell division even though the circadian rhythm is normal in these cells. Here we report that tumor-driven Lewis Lung Carcinoma (LLC) cells have perfectly temperature compensated circadian clocks, but the periods of their cell cycle gene expression rhythms are temperature-dependent, suggesting that their circadian and cell cycles are not connected. These data support our hypothesis that decoupling of the circadian and cell cycles may underlie aberrant cell division in tumor cells.

Behavioral Regularity in Infancy Predicts Lower Anxiety Years Later

Back to table of contents Previous article Next article Clinical & Research NewsFull AccessBehavioral Regularity in Infancy Predicts Lower Anxiety Years LaterMark MoranMark MoranSearch for more papers by this authorPublished Online:3 Sep 2010https://doi.org/10.1176/pn.45.17.psychnews_45_17_030AbstractLack of regularity in sleeping, eating, and play routines in infancy appears to be associated with risk for anxiety in childhood.Infants with irregular patterns of sleeping, eating, and playing were significantly more likely to experience symptoms of anxiety more than a decade later, according to a prospective study of 59 children followed for 13 years beginning at age 1 month. The report was published online in the July Psychiatry Research.“The study indicates there are long-term implications for early behavioral regularity,” co-author Linnea Burk, Ph.D., of the Wisconsin Psychiatric Institute and Clinics, told Psychiatric News. “Clinicians have long advocated for predictable care and sleep schedules for children, and this study provides clear support that these steps are not only important in the short run, while the children are young, but also to long-term outcomes in adolescence.”Beginning in 1990 and 1991 as part of the Wisconsin Study of Families and Work, parents of 59 infants completed a diary tool called the Baby Social Rhythm Metric (Baby SRM), devised by the researchers to document lifestyle routines and sleep patterns a week at a time. The diary was a structured instrument that required parents to write down the starting time for each of four other major daily events in the infant's life—feeding, playing, diaper changing, and receiving comfort. There were 30 baby girls and 29 baby boys.(The Wisconsin Study of Families and Work is a much larger prospective study of child development that has yielded a number of published papers. Information about the study is posted at <www.wsfw.us>.)Follow-up information was collected on “sociability” at ages 4 months and 12 months as measured by the Infant Behavior Questionnaire, and on symptoms of depression and anxiety in children up to age 13. A measure of children's “directed attention”—reflecting the ability to focus attention on specific tasks and environmental exploration—was obtained from videotaped observations of a two-hour home visit when children were 4.5 years of age.Separately, and only after follow-up data were gathered, an algorithm was developed that cast the four specified events measured in the Baby SRM into 12 two-hour segments covering the 24-hour day. The resulting metric related to how spread out around the clock the events were (reflecting a low SRM score and a high degree of irregularity) or the extent to which particular times of day predominated for each of the events (reflecting a high SRM score and a high degree of regularity).The Baby SRM score ranged from 0 (least regular) to 7 (most regular).The researchers found that a higher SRM score was associated with lower overall levels of anxiety symptoms in childhood. There was no significant correlation of Baby SRM with childhood depression.Timothy Monk, Ph.D., a professor of psychiatry and director of the human chronobiology research program at the University of Pittsburgh, noted that an extensive body of research in adults has shown circadian rhythm is associated with mental health.“These new findings in infants reinforce this view,” he said. “In terms of treating patients both young and old, it is worth encouraging patients to adopt, to the extent that they can, a highly regular daily life style with predictable timing of bedtime, rise time, meals, and work.”Moreover, sociability and directed attention were both correlated with Baby SRM scores and with school-age anxiety and may serve as mediating factors.“Greater regularity to daily activities may increase the predictability of infant demands, leading to enhanced parental perception of need cues and increased parental confidence, which further strengthens caretaking routines,” the researchers stated. “Thus, greater regularity in daily activities may enhance early parent–infant relationships, improve infant regulatory capacity, and promote environmental exploration as internal resources are available.”This study was supported in part by funding from the National Institute of Mental Health, the National Institutes of Health, and the John D. and Catherine T. MacArthur Foundation.Child psychiatrist and APA Treasurer David Fassler, M.D., said the results of the study are consistent with previous reports and with general clinical experience. “We're well aware that young infants display a range of distinct temperaments,” he said. “We also know that many of these early characteristics persist throughout childhood and into adulthood. The present study demonstrates that anxiety in childhood correlates with specific behavior patterns observed during infancy.“The behavior of infants clearly affects and alters the nature of their interaction with their parents and other caregivers, which could easily influence emotional development from an early age,” Fassler said. “We also know that the expression of anxiety has a significant genetic component, elements of which could conceivably influence behavioral regularity during infancy.”“Behavioral Circadian Regularity at Age 1 Month Predicts Anxiety Levels During School-Age Years” is posted at <www.sciencedirect.com/science/journal/01651781>. ISSUES NewArchived

Does the Specific Time of Day Used to Capture Data on Ventilator-Days Have an Impact on the Documented Rates of Ventilator-Associated Pneumonia?

Definitions of ventilator-associated pneumonia do not note a preferred daily time for obtaining denominator data. We examined collecting data on the number of ventilator-days at different times of day in 7 intensive care units. Rates of ventilator-associated pneumonia did not significantly differ when denominator data were collected at midnight, 8 am, or 4 pm, supporting standard definitions.

Preprocessing techniques for context recognition from accelerometer data

The ubiquity of communication devices such as smartphones has led to the emergence of context-aware services that are able to respond to specific user activities or contexts. These services allow communication providers to develop new, added-value services for a wide range of applications such as social networking, elderly care and near-emergency early warning systems. At the core of these services is the ability to detect specific physical settings or the context a user is in, using either internal or external sensors. For example, using built-in accelerometers, it is possible to determine whether a user is walking or running at a specific time of day. By correlating this knowledge with GPS data, it is possible to provide specific information services to users with similar daily routines. This article presents a survey of the techniques for extracting this activity information from raw accelerometer data. The techniques that can be implemented in mobile devices range from classical signal processing techniques such as FFT to contemporary string-based methods. We present experimental results to compare and evaluate the accuracy of the various techniques using real data sets collected from daily activities.

The neurobiology of preovulatory and estradiol-induced gonadotropin-releasing hormone surges.

Ovarian steroids normally exert homeostatic negative feedback on GnRH release. During sustained exposure to elevated estradiol in the late follicular phase of the reproductive cycle, however, the feedback action of estradiol switches to positive, inducing a surge of GnRH release from the brain, which signals the pituitary LH surge that triggers ovulation. In rodents, this switch appears dependent on a circadian signal that times the surge to a specific time of day (e.g., late afternoon in nocturnal species). Although the precise nature of this daily signal and the mechanism of the switch from negative to positive feedback have remained elusive, work in the past decade has provided much insight into the role of circadian/diurnal and estradiol-dependent signals in GnRH/LH surge regulation and timing. Here we review the current knowledge of the neurobiology of the GnRH surge, in particular the actions of estradiol on GnRH neurons and their synaptic afferents, the regulation of GnRH neurons by fast synaptic transmission mediated by the neurotransmitters gamma-aminobutyric acid and glutamate, and the host of excitatory and inhibitory neuromodulators including kisspeptin, vasoactive intestinal polypeptide, catecholamines, neurokinin B, and RFamide-related peptides, that appear essential for GnRH surge regulation, and ultimately ovulation and fertility.

Colored Sweat Caused by Pseudochromhidrosis

Letters2 February 2010Colored Sweat Caused by PseudochromhidrosisGeorge S. Panagoulias, MD, Christos St. Basagiannis, MD, Nicholas Tentolouris, MD, Evgenia Stavropoulou, MD, and Lazaros Karnesis, MDGeorge S. Panagoulias, MDFrom Athens University Medical School, Laiko General Hospital, Athens GR-11527, Greece; and 401 General Military Hospital of Athens, Athens GR-11525, Greece.Search for more papers by this author, Christos St. Basagiannis, MDFrom Athens University Medical School, Laiko General Hospital, Athens GR-11527, Greece; and 401 General Military Hospital of Athens, Athens GR-11525, Greece.Search for more papers by this author, Nicholas Tentolouris, MDFrom Athens University Medical School, Laiko General Hospital, Athens GR-11527, Greece; and 401 General Military Hospital of Athens, Athens GR-11525, Greece.Search for more papers by this author, Evgenia Stavropoulou, MDFrom Athens University Medical School, Laiko General Hospital, Athens GR-11527, Greece; and 401 General Military Hospital of Athens, Athens GR-11525, Greece.Search for more papers by this author, and Lazaros Karnesis, MDFrom Athens University Medical School, Laiko General Hospital, Athens GR-11527, Greece; and 401 General Military Hospital of Athens, Athens GR-11525, Greece.Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-152-3-201002020-00024 SectionsAboutFull TextPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail Background: Pseudochromhidrosis and chromhidrosis are conditions associated with colored sweat. Pseudochromhidrosis is production of colorless sweat that becomes colored when it reaches the skin and combines with other agents, whereas chromhidrosis is a rare condition associated with production of colored sweat by apocrine sweat glands.Objective: To report a case of a patient with pseudochromhidrosis.Case Report: A 36-year-old white man presented with a 2-year history of brown-black sweat on his face, neck, and thorax. Colored sweat was intermittent and was not related to a specific time of day, body position, or food consumption but was pronounced after participation in ...

A circadian clock in Saccharomyces cerevisiae

Circadian timing is a fundamental biological process, underlying cellular physiology in animals, plants, fungi, and cyanobacteria. Circadian clocks organize gene expression, metabolism, and behavior such that they occur at specific times of day. The biological clocks that orchestrate these daily changes confer a survival advantage and dominate daily behavior, for example, waking us in the morning and helping us to sleep at night. The molecular mechanism of circadian clocks has been sketched out in genetic model systems from prokaryotes to humans, revealing a combination of transcriptional and posttranscriptional pathways, but the clock mechanism is far from solved. Although Saccharomyces cerevisiae is among the most powerful genetic experimental systems and, as such, could greatly contribute to our understanding of cellular timing, it still remains absent from the repertoire of circadian model organisms. Here, we use continuous cultures of yeast, establishing conditions that reveal characteristic clock properties similar to those described in other species. Our results show that metabolism in yeast shows systematic circadian entrainment, responding to cycle length and zeitgeber (stimulus) strength, and a (heavily damped) free running rhythm. Furthermore, the clock is obvious in a standard, haploid, auxotrophic strain, opening the door for rapid progress into cellular clock mechanisms.

Analyzing the Characteristics of Consumers Shopping at a Particular Time of Day in the Farmers^|^rsquo; Market in an Urban Area:

Analyzing the Characteristics of Consumers Shopping at a Particular Time of Day in the Farmers^|^rsquo; Market in an Urban Area:

THE CIRCADIAN CLOCK GENE PER1 SUPPRESSES CANCER CELL PROLIFERATION AND TUMOR GROWTH AT SPECIFIC TIMES OF DAY

Cell cycle progression is tightly regulated. The expressions of cell cycle regulators, the products of which either promote or inhibit cell proliferation, oscillate during each cell cycle. Cellular proliferation and the expression of cell cycle regulators are also controlled by the circadian clock. Disruption of the circadian clock may thereby lead to deregulated cell proliferation. Mammalian Per2 is a core clock gene, the product of which suppresses cancer cell proliferation and tumor growth in vivo and in vitro. Because Per1, another key clock gene, is mutated in human breast cancers, and because its clock functions are similar and complementary to those of Per2, we have studied its role in modulating breast cancer cell proliferation and tumor growth. We find that breast cancer growth rate is gated by the circadian clock with two daily peaks and troughs, and that they are coupled to the daily expression patterns of clock-controlled genes that regulate cell proliferation. Down-regulation of the expression of tumor Per1 increases cancer cell growth in vitro and tumor growth in vivo by enhancing the circadian amplitude of the two daily tumor growth peaks. The data of the study suggest Per1 has tumor-suppressor function that diminishes cancer proliferation and tumor growth, but only at specific times of day. (Author correspondence: williamhrushesky@gmail.com).

Tropical Cyclone Tornadoes, 1950–2007

Abstract An expanded “climatology” of U.S. tropical cyclone (TC) tornadoes covering the period 1950–2007 is presented. A major climatology published in 1991 included data on 626 TC tornadoes. Since then, almost 1200 more TC tornado records have been identified, with almost half of that number from the 2004–05 seasons alone. This work reexamines some findings from previous studies, using a substantially larger database. The new analyses strongly support distinctions between inner- and outer-region tornadoes, which were suggested in previous studies. Outer-region tornadoes (beyond 200 km from the TC center) have a stronger diurnal signal, commonly occurring during the afternoon. Inner-region tornadoes typically occur within ∼12 h of TC landfall, with no strong preference for a particular time of day. They are disproportionately less damaging tornadoes, with more rated F0 than in the outer-region sample. In more general terms, the TC tornado database includes a smaller percentage of significant (≥F2) tornadoes (14%) than does the overall U.S. tornado database (22%). Most TC tornadoes (60%) occur within 100 km of the coast; this includes core-region tornadoes near the time of landfall as well as tornadoes from rainbands coming ashore far from the circulation center. The F0-rated tornadoes are slightly more common near the coast but compose a smaller percentage of the tornadoes inland. The threat often persists for 2–3 days after landfall and extends ∼400 km inland and ∼500 km from the TC center, although there is much case-to-case variability. This puts locations at risk that might otherwise avoid damage from the TC.

Is there a circadian variation of epileptiform abnormalities in idiopathic generalized epilepsy?

Epileptiform abnormalities often occur at specific times of day or night, possibly attributable to state of consciousness (sleep vs. wake) and/or influences from the endogenous circadian pacemaker. In this pilot study we tested for the existence of circadian variation of interictal epileptiform discharges (IEDs), independent of changes in state, environment, or behavior. Five patients with generalized epilepsy underwent a protocol whereby their sleep/wake schedule was evenly distributed across the circadian cycle while undergoing full-montage electroencephalography and hourly plasma melatonin measurements. Light was <8 lux to prevent circadian entrainment. All patients completed the protocol, testifying to its feasibility. All patients had normal circadian rhythmicity of plasma melatonin relative to their habitual sleep times. In the three patients with sufficient IEDs to assess variability, most IEDs occurred during non-rapid eye movement (NREM) sleep (ratio NREM:wake = 14:1, P < 0.001). In both patients who had NREM at all circadian phases, there was apparent circadian variation in IEDs but with different phases relative to peak melatonin.

Espectro alimentar e variação sazonal da dieta de Plagioscion squamosissimus (Heckel, 1840) (Osteichthyes, Sciaenidae) na lagoa do Piató, Assu, Estado do Rio Grande do Norte, Brasil

The diet and seasonal variations in the feeding of Plagioscion squamosissimus were evaluated. Fishes were captured monthly at the Piató Lagoon, Assu, Rio Grande do Norte State, from August of 2004 to July of 2005, examined at a specific time of day. In laboratory, after obtaining the biometric data, fishes were opened and the guts extracted. The stomach contents were analyzed under stereoscopic microscope, and its items were identified and their volume was measured. Occurrence and volumetric frequencies and the food index were calculated. The items were grouped in seven main categories; shrimp and insects were predominant. The item classification made it possible to classify the species as carnivorous with carcinophagous-insectivore tendencies. In respect to seasonal variations, an alteration of the main items was observed according to the seasons, where insects prevailed in the dry season and shrimp stood out in the rainy season. In regards to capture periods, a twilight-nocturnal habit was observed, and activity periods are also marked by differences in the food type consumed, as shrimp prevailed in lower light and insects in brighter times.

Time Of Habitual Training Does Not Alter Circadian Rhythm Of Swim Performance

Some studies have found better athletic performance at the usual time of training relative to other times of day. These results could reflect either a change in the circadian system or a non-circadian adaptation that results in better performance at the accustomed time of training. However, other studies have provided equivocal or negative results. PURPOSE: To examine whether the circadian rhythm of swim performance differs between individuals who habitually train at a certain time(s) of day compared to those who do not. METHODS: 25 swimmers were assessed for 50-55 consecutive hr in the laboratory while adhering to a 3-hr ultra-short sleep/wake cycle, a common chronobiological technique. Swimmers performed 6 maximal 200-m swims, with each trial separated by 9 hr. Performances were z-transformed and expressed relative to time of day. The time of habitual training for each swimmer was obtained via questionnaire prior to the study. Estimates of swim performance rhythm amplitude (i.e., range of performance), acrophase (i.e., time of peak performance), and mesor (i.e., fitted mean value) were obtained via cosinor analysis and compared between groups with independent sample t-tests. Group data were analyzed via ANCOVA with trial number as a covariate and time of day and habitual training time as fixed factors. RESULTS: Approximately ½ of the swimmers (n=12) reported no usual time of training. The half (n=13) who had habitual swim times trained daily between 0600-0900 hr, 1600-1800 hr, or at both of these times of day. Those who reported a habitual time of training had lower mesors (i.e., faster swim time; p<0.001), but did not have different performance rhythm acrophases or amplitudes compared to those without a specific time of training (n=12). No group differences were found in swim performance when analyzed via ANCOVA. CONCLUSIONS: This study found minimal evidence of different swim performance rhythm characteristics between those who habitually trained at a particular time of day versus those who did not. No evidence was found for superior performance that was specific to the usual time of training. However, the data do not discount the possibility that such an advantage might be observed under usual diurnal conditions, due to variations in diet, sleep, rest, and performance preparation.

Incentive Payments to Academic Anesthesiologists for Late Afternoon Work Did Not Influence Turnover Times

Anesthesiologists are often paid extra for hours worked in the late afternoon and evening. Although anesthesiologists have little influence on their operating room (OR) assignments and workloads late in the afternoon, they can influence turnover times. OR turnover times on workdays were reviewed for n = 30 mo before there was incremental pay, for n = 15 mo with incremental pay for work past 3:30 pm, and for n = 8 mo with pay for work past 4:00 pm. The end point was the percentage of turnovers that were prolonged, defined as longer than 1 h. Turnovers straddling 3:30 pm (n = 3945), 4:00 pm (n = 3602), and 5:00 pm (n = 2834) were studied, as were those straddling 2:00 pm (n = 4407) as a control. In addition, qualitative (survey) assessment of n = 30 anesthesiologists was performed the last month to learn about their opinions on working late on weekdays. Most respondents considered an OR to run late if it finished after a specific time of day (87%, P < 0.001), unrelated to the room's type of procedures (90%, P < 0.001) or to the payment for working after 4:00 pm (100%, P < 0.001). There was no significant effect of implementation or changes to the incentive program on the incidences of prolonged turnover times at each of the studied times in the afternoon (all P > 0.14). Our results suggest that hospital administrators, deans, and other executives need not be especially concerned about disincentives produced by methods of internal compensation of anesthesiologists on highly visible OR turnover times late in afternoons.

The GABAA Receptor RDL Acts in Peptidergic PDF Neurons to Promote Sleep in Drosophila

Sleep is regulated by a circadian clock that times sleep and wake to specific times of day and a homeostat that drives sleep as a function of prior wakefulness. To analyze the role of the circadian clock, we have used the fruit fly Drosophila. Flies display the core behavioral features of sleep, including relative immobility, elevated arousal thresholds, and homeostatic regulation. We assessed sleep-wake modulation by a core set of circadian pacemaker neurons that express the neuropeptide PDF. We find that disruption of PDF function increases sleep during the late night in light:dark and the first subjective day of constant darkness. Flies deploy genetic and neurotransmitter pathways to regulate sleep that are similar to those of their mammalian counterparts, including GABA. We find that RNA interference-mediated knockdown of the GABA(A) receptor gene, Resistant to dieldrin (Rdl), in PDF neurons reduces sleep, consistent with a role for GABA in inhibiting PDF neuron function. Patch-clamp electrophysiology reveals GABA-activated picrotoxin-sensitive chloride currents on PDF+ neurons. In addition, RDL is detectable most strongly on the large subset of PDF+ pacemaker neurons. These results suggest that GABAergic inhibition of arousal-promoting PDF neurons is an important mode of sleep-wake regulation in vivo.