bluuebunny/crossref_metadata_2025 huggingface dataset:
The Inner Voice in Writing
Authors: Chenoweth N. Ann , Hayes John R.
Published: May 2004

This study explores the connection between writing and working memory, specifically the role of the subvocal articulatory rehearsal process (or inner voice). The authors asked the 18 participants to type sentences describing 24 multipanel cartoons. In some conditions, the participants were required to repeat a syllable continuously while writing. This activity, called articulatory suppression, interferes with the articulatory rehearsal process. Results indicated that interfering with the articulatory rehearsal process (or inner voice) interferes with writing by slowing the rate of writing, increasing mechanical errors, changing the temporal microstructure of text production, and increasing the perceived difficulty of the writing task. The authors applied their model of written text production to provide a theoretical account for these results.
Spreading Chaos
Authors: Paul Danette
Published: May 2004

Scientific popularizations are generally considered translations (often dubious ones) of scientific research for a lay audience. This study explores the role popularizations play within scientific discourse, specifically in the development of chaos theory. The methods included a review of the popular and the semipopular books on chaos theory from 1975 to 1995, interviews with key figures, and an analysis of the citations in scientific research journals to Gleick’s well-known popularization, Chaos: Making a New Science. The results indicate that popularizations take different forms as a scientific revolution develops into normal science. At various points, popularizations are used by scientists to find a broad, interdisciplinary, scientific audience, to show interest in the field, to disseminate lines of inquiry, and to help establish the author’s priority claim.
The Case of the Hebrew Press
Authors: Soffer Oren
Published: May 2004

Following the scientific revolution, the modern perception of discourse assumed that text can and should reflect, in a literal way, objective reality as observed in the real world. This perception is radically different from a traditional religious perception of discourse in general and from the Jewish perception in particular. The Jewish traditional perception was based upon intertextual (and not empirical) models of inquiry and endeavored to uncover concealed levels within texts through analytical-philological methods. It is argued that the revival of Hebrew as a secular language went hand in hand with the adoption of the modern perception of discourse. This adoption involved a change in the relationship between text, knowledge, and reality within Jewish society, which found explicit expression in the Hebrew journals established in the middle of the 19th century.
Guess Who’s Coming to Dinner: A Discursus on Knowledge, Power, and Presence in “A Symposium”
Authors: Guy Talmadge C.
Published: May 2004

This article critiques the predominantly Eurocentric and phallocentric focus of Rachal’s “A Symposium,” recently published in Adult Education Quarterly. It is argued that Rachal constructs a dialogue that privileges a philosophical canon whose continued legitimacy is being challenged both in philosophical and adult education circles. The form of presentation in “A Symposium,” the Socratic method, belies the universal and eternal nature of knowledge, a theme that is evident throughout “A Symposium”’s dialogue. Also questioned is the selection of guests to the dinner party as reflecting a male and Eurocentric bias that masks the centrality of identity, social location, and power in the construction of knowledge. “A Symposium” represents a missed opportunity to raise some critical and substantive issues of relevance to adult educators concerning the construction and consequence of knowledge as reflected in current educational and philosophical debates on knowledge and power.
Adolescent Mothers in a Transitional Living Facility
Authors: Schwartz Ann E. , McRoy Ruth G. , Downs A. Chris
Published: May 2004

Most of the research literature on attachment and adolescent transitions has addressed youth in family settings. This article explores these issues with a sample of 25 pregnant and parenting teens living in a transitional shelter. Using case records and interviewdata as well as results of standardized measures of depression, self-esteem, child abuse potential, and emotional autonomy, insights on relationships between adolescent mothers and their parents, romantic partners, staff, and children are explored, and implications are provided for agencies serving this population.
Preventing Poor Mental Health and School Dropout of Mexican American Adolescents Following the Transition to Junior High School
Authors: Gonzales Nancy A. , Dumka Larry E. , Deardorff Julianna , Carter Sara Jacobs , McCray Adam
Published: May 2004

This study provided an initial test of the Bridges to High School Program, an intervention designed to prevent school disengagement and negative mental health trajectories during the transition to junior high school. The intervention included an adolescent coping skills intervention, a parenting skills intervention, and a family strengthening intervention. The program was evaluated by examining pretest to posttest changes on targeted mediators and outcomes with a sample of 22 predominantlyMexican American families. Adolescents reported increased use of active and distraction coping strategies, and decreased depressive symptoms for themselves from pretest to posttest. They also reported significant changes in their mothers’parenting skills, including increased monitoring and a decrease in inconsistent discipline. Maternal caregivers reported an increase in supportive parenting and a decrease in inconsistent discipline for themselves and fewer adolescent problem behaviors. Process evaluations confirmed the attractiveness and perceived helpfulness of the program.
Assessment of High School Students’ Understanding of DSM-IV-MR-J Items
Authors: Pelletier Amélie , Ladouceur Robert , Fortin Josée-Mélanie , Ferland Francine
Published: May 2004

The current study examines the understanding of the DSM-IV-MR-J items to assess pathological gambling among adolescents aged 12 to 15, and explores its accuracy. The DSM-IV-MR-J was first administered in the classroom. Participants were assigned to either an experimental or a control group. Participants in the first group were asked to explain the meaning of each DSM-IV-MR-J item during an individual interview. If the item was not properly understood, the investigator corrected the participant’s understanding of the item. The questionnaire was then administered a second time. The control group was only submitted to a test-retest procedure. The results showed that 22% of the items were misunderstood. Changes in diagnostic categories emerged on the second administration for both groups. A 20% and 29.4% decrease in the number of problem/pathological gamblers was observed in the experimental and control group. The implications of these results are discussed in terms of the reliability of the DSM-IV-MR-J as a measure of problem gambling among adolescents.
Peer Relationships Among Institutionalized Juvenile Boys
Authors: Preveaux Neal E. , Ray Glen E. , LoBello Steven G. , Mehta Sheila
Published: May 2004

This study examined peer relationships (sociometric status and friendship) of institutionalized juvenile males ages 12 to 18. Results replicated previous studies using “normal” nondelinquent samples demonstrating that sociometrically popular status juveniles were evaluated higher on sociability and leadership than were average- or rejected-status juveniles. Furthermore, rejected-status juveniles were evaluated as being more aggressive and more actively isolated than were popular- or average-status juveniles. Investigating the relationship between friendship networks (perceived and reciprocated) and social status revealed no differences. However, differences in relationship quality as a function of sociometric status emerged with rejected-status juveniles evaluating their best-friend relationship as being more caring, intimate, exclusive, and less conflict ridden than popular or average-status juveniles’ evaluations of their best-friend relationships. Findings replicate and extend previous research investigating children’s peer relationships. Implications for future research into the juvenile’s understanding of peer relationships are discussed.
Internal and External Developmental Assets Among African American Male Gang Members
Authors: Taylor Carl S. , Lerner Richard M. , von Eye Alexander , Bobek Deborah L. , Balsano Aida Bilalbegović , Dowling Elizabeth M. , Anderson Pamela M.
Published: May 2004

The presence of individual and ecological assets for positive development was assessed through data derived from individual interviews with 45 African American adolescent male members of inner-city Detroit gangsand50 African American adolescent males living in the same communities but involved in community-based organizations (CBOs) aimed at promoting positive youth development.The CBO youth had higher levels of both domains of assets. However, all gang members possessed at least one asset, and 15.6% of the gang youth had a total mean asset score that was above the total mean asset score of the CBO youth. In turn, the asset scores for the former group were significantly more likely to be correlated than was the case for the later group. The implications of these findings are discussed in regard to the idea that all youth possess the potential for positive development and to the nature of policies and programs pertinent to enhancing the life chances of diverse youth.
Connection and Regulation at Home and in School
Authors: Gregory Anne , Weinstein Rhona S.
Published: May 2004

Qualities of adolescent-adult relationships across home and school environments are examined as predictors of academic growth in mathematics. An ethnically diverse sample of adolescents was drawn from the National Educational Longitudinal Study, 1988. In separate analyses, adolescents’perceptions of (a) connection with parents and teachers and (b) regulation from parents and teachers uniquely predicted academic growth in math from 8th to 12th grade. Thus, assets across home and school were additive. No evidence supported a compensatory process in which less connection or regulation at home was compensated by the presence of these experiences in school. Within school, teacher connection was the strongest predictor for all adolescents, but a combination of connection and regulation, making up an authoritative teaching style, predicted even greater academic growth in math for adolescents from low socioeconomic backgrounds.
Contributions of Parenting and Campus Climate to Freshmen Adjustment in a Multiethnic Sample
Authors: Mounts Nina S.
Published: May 2004

The role of parental support, hostile campus racial climate, and sense of belonging to campus in predicting psychological adjustment and drug use was examined in a sample of 319 African American and White college freshmen. No ethnic-group differences were found for mean levels of parental support, racial hostility, belonging to campus, or psychological adjustment. White adolescents reported higher levels of drug and alcohol use than did African American adolescents. Drug use was related to anxiety and depression for White adolescents but not for African American adolescents. For both ethnic groups, higher perceptions of racial hostility were related to higher levels of adjustment problems and binge drinking. Higher levels of parental support were related to lower levels of depression and loneliness for both ethnic groups. Modest support for belonging to campus as a mediator between parental support and hostile racial climate and the outcomes was found, with more evidence for African American adolescents than for White adolescents.
Seasonal Variation of Depression and Other Moods: A Longitudinal Approach
Authors: Harmatz Morton G. , Well Arnold D. , Overtree Christopher E. , Kawamura Kathleen Y. , Rosal Milagros , Ockene Ira S.
Published: May 2004

The present study examined the effect of season of the year on depression and other moods. Previous work, primarily cross sectional or retrospective in design and involving clinically depressed or seasonally affective disordered samples, has suggested that mood changes as a function of season. However, the literature also shows conflicting and/or inconsistent findings about the extent and nature of this relationship. Importantly, these prior studies have not adequately answered the question of whether there is a seasonal effect in nondepressed people. The present study employed a longitudinal design and a large sample drawn from a normal population. The results, based on those participants for whom mood measures were collected in each season, demonstrated strong seasonal effects. Beck Depression Inventory (BDI) scores were highest in winter and lowest in summer. Ratings on scales of hostility, anger, irritability, and anxiety also showed very strong seasonal effects. Further analyses revealed that seasonal variation in BDI scores differed for females and males. Females had higher BDI scores that showed strong seasonal variation, whereas males had lower BDI scores that did not vary significantly across season of the year.
Circadian Regulation of Visually Evoked Potentials in the Domestic Pigeon, Columba livia
Authors: Wu Wen Qi , McGoogan Jennifer M. , Cassone Vincent M.
Published: May 2004

The avian circadian and visual systems are integrally related and together influence many aspects of birds’ behavior and physiology. Certainly, light cycles and their visual perception are the major zeitgebers for circadian rhythms, but do circadian rhythms affect vision? To assess whether visual function is regulated on a circadian basis, flash-evoked electroretinograms (ERGs) and vision-evoked potentials (VEPs) from the optic tectum (TeO) were recorded simultaneously in domestic pigeons at different circadian phases in a light-dark regime (LD) and in constant darkness (DD), while feeding activity was measured to determine circadian phase. In both LD and DD, the amplitudes of ERG b-waves were higher during the day than at night and latencies of a and b-waves were longer at night. The median effective intensity for ERG a-wave was marginally higher during the day than during the night, indicating greater sensitivity at night, but this rhythm did not persist in DD. The amplitudes of TeO VEPs were also greater during the day, and latencies were greater at night in LD and DD. Together, the data indicate that a circadian clock regulates pigeon visual function at several integrative levels.
Relationship between Norepinephrine Release in the Hypothalamic Paraventricular Nucleus and Circulating Prolactin Levels in the Siberian Hamster: Role of Photoperiod and the Pineal Gland
Authors: Imundo Jason , Bielefeld Eric , Dodge James , Badura Lori L.
Published: May 2004

The impact of norepinephrine (NE) and its metabolite, 3-methoxy-4-hydroxyphenylglycol (MHPG), on circulating prolactin (PRL) was evaluated in the paraventricular region of the hypothalamus as a function of photoperiod and integrity of the pineal gland. In Experiment 1, whole tissue content of NE and MHPG was assessed in male and female hamsters that had been pinealectomized or sham-pinealectomized and exposed to long or short photoperiods for 5 weeks. The results revealed a marginal effect of photoperiod in males, but no overall effects of surgery. Because analysis of whole tissue content can be complicated by concurrent changes in synthesis and storage rates, Experiment 2 was conducted using microdialysis to assess extracellular levels of NE and MHPG in female hamsters. Pinealectomy completely prevented the short-day-induced suppression of luteinizing hormone, but it only partially prevented the effects of short days on PRL. Furthermore, both NE and MHPGlevels were significantly elevated in short-day-exposed pinealectomized and shamoperated animals. These results suggest that NErelease within the paraventricular nucleus inhibits the circulating PRL levels and is one mechanism by which direct photic information can influence the neuroendocrine axis independently of the pineal melatonin signal.
Is Self-Reported Morbidity Related to the Circadian Clock?
Authors: Taillard Jacques , Philip Pierre , Chastang Jean-François , Diefenbach Konstanze , Bioulac Bernard
Published: May 2004

Morningness and eveningness preference, an endogenous component of the circadian clock, is characterized by an interindividual difference in circa- dian phase and requires of humans a specific timing of behavior. The biological rhythms of morning and evening types are consequently phase shifted with fixed socioeconomic constraints. The impact of this phase shift on health is widely debated. The purpose of the authors' study was to determine the influence of morningness/eveningness preference on self-reported morbidity and health in an active population. A total of 1165 nonshift workers of the French national electrical and gas company, enrolled in the GAZELcohort and aged 51.3 ± 3.3 years, were included in this study. They replied by mail with a completed questionnaire, including morningness/eveningness preference, self-reported morbidity, subjective sleep patterns, and daytime somnolence and sleeping schedules for 3 weeks, during the spring of 1997. Annual self-reported health impairments were assessed with the annual general questionnaire of the GAZEL cohort for 1997. After adjustment for age, sex, and occupational status, morningness-like and eveningness-like participants reported a specific worse self-reported morbidity. Whereas morningness was associated with worse sleep ( p = 0.0001), eveningness was associated with feeling less energetic ( p = 0.04) and physical mobility ( p = 0.02). These relationships were observed even in good sleepers, except for physical mobility. After adjustment for confounding variables, eveningness-like participants reported more sleep ( p = 0.0004) and mood ( p = 0.00018) disorders than morningness-like participants. Morningness/ eveningness preference was related to specific chronic complaints of insomnia: morningness was related with difficulty in maintaining sleep ( p = 0.0005) and the impossibility to return to sleep in the early morning ( p = 0.0001) (sleep phase-advance syndrome); eveningness was related with difficulty in initiating sleep ( p = 0.0001) and morning sleepiness ( p = 0.0001). In good sleepers, morningness was related with sleep phase-advance syndrome ( p = 0.0001) and eveningness with morning sleepiness ( p = 0.0001). In conclusion, the expression (phase advance or delay) of the circadian clock could be related to worse self-reported morbidity and health. These findings must be verified by further epidemiological studies, but they suggest that the impossibility to return to sleep in the early morning is not only associated with age.
Mammalian Photoperiodic System: Formal Properties and Neuroendocrine Mechanisms of Photoperiodic Time Measurement
Authors: Goldman Bruce D.
Published: May 2004

Photoperiodism is a process whereby organisms are able to use both absolute measures of day length and the direction of day length change as a basis for regulating seasonal changes in physiology and behavior. The use of day length cues allows organisms to essentially track time-of-year and to “anticipate” relatively predictable annual variations in important environmental parameters. Thus, adaptive types of seasonal biological changes can be molded through evolution to fit annual environmental cycles. Studies of the formal properties of photoperiodic mechanisms have revealed that most organisms use circadian oscillators to measure day length. Two types of paradigms, designated as the external and internal coincidence models, have been proposed to account for photoperiodic time measurement by a circadian mechanism. Both models postulate that the timing of light exposure, rather than the total amount of light, is critical to the organism’s perception of day length. In mammals, a circadian oscillator(s) in the suprachiasmatic nucleus of the hypothalamus receives photic stimuli via the retinohypothalamic tract. The circadian system regulates the rhythmic secretion of the pineal hormone, melatonin. Melatonin is secreted at night, and the duration of secretion varies in inverse relation to day length; thus, photoperiod information is “encoded” in the melatonin signal. The melatonin signal is presumably “decoded” in melatonin target tissues that are involved in the regulation of a variety of seasonal responses. Variations in photoperiodic response are seen not only between species but also between breeding populations within a species and between individuals within single breeding populations. Sometimes these variations appear to be the result of differences in responsiveness to melatonin; in other cases, variations in photoperiod responsiveness may depend on differences in patterns of melatonin secretion related to circadian variation. Sites of action for melatonin in mammals are not yet well characterized, but potential targets of particular interest include the pars tuberalis of the pituitary gland and the suprachiasmatic nuclei. Both these sites exhibit uptake of radiolabeled melatonin in various species, and there is some evidence for direct action of melatonin at these sites. However, it appears that there are species differences with respect to the importance and specific functions of various melatonin target sites.
Encoding Le Quattro Stagioni within the Mammalian Brain: Photoperiodic Orchestration through the Suprachiasmatic Nucleus
Authors: Schwartz William J. , de la Iglesia Horacio O. , Zlomanczuk Piotr , Illnerová Helena
Published: May 2004

Within the suprachiasmatic nucleus (SCN) is a pacemaker that not only drives circadian rhythmicity but also directs the circadian organization of photoperiodic (seasonal) timekeeping. Recent evidence using electrophysiological, molecular, and genetic tools now strongly supports this conclusion. Important questions remain regarding the SCN’s precise role(s) in the brain’s photoperiodic circuits, especially among different species, and the cellular and molecular mechanisms for its photoperiodic “memory.” New data suggesting that SCN “clock” genes may also function as “calendar” genes are a first step toward understanding how a photoperiodic clock is built from cycling molecules.
Of Rodents and Ungulates and Melatonin: Creating a Uniform Code for Darkness by Different Signaling Mechanisms
Authors: Stehle Jörg H. , von Gall Charlotte , Schomerus Christof , Korf Horst-Werner
Published: May 2004

Melatonin synthesis in the mammalian pineal gland is one of the best investigated output pathways of the circadian clock because it can be readily measured and is tightly regulated by a clearly defined input, the neurotransmitter norepinephrine. In this system, a regulatory scenario was deciphered that is centered around the cyclic AMP pathway but shows peculiar species-specific differences. In rodents, the cyclic AMP–mediated, temporally sequential up-regulation of two transcription factors, the activator CREB (cyclic AMP–responsive elementbinding protein) and the inhibitor ICER (inducible cyclic AMP–dependent early repressor), is the core mechanism to determine rhythmic accumulation of the mRNA encoding for the rate-limiting enzyme in melatonin synthesis, the arylalkylamine N-acetyltransferase (AA-NAT). Thus, in rodents, the regulation of melatonin synthesis bears an essential transcriptional component, which, however, is flanked by posttranscriptional mechanisms. In contrast, in ungulates, and possibly also in primates, AA-NAT appears to be regulated exclusively on the posttranscriptional level. Here, increasing cyclic AMP levels inhibit the breakdown of constitutively synthesized AA-NAT protein by proteasomal proteolysis, leading to an elevated enzyme activity. Thus, self-restriction of cellular responses, as a reaction to external cues, is accomplished by different mechanisms in pinealocytes of different mammalian species. In such a temporally gated cellular adaptation, transcriptionally active products of clock genes may play a supplementary role. Their recent detection in the endogenously oscillating nonmammalian pineal organ and, notably, also in the slave oscillator of the mammalian pineal gland underlines that the mammalian pineal gland will continue to serve as an excellent model system to understand mechanisms of biological timing.
Insect Photoperiodism and Circadian Clocks: Models and Mechanisms
Authors: Tauber Eran , Kyriacou Bambos Panayiotis
Published: May 2004

Photoperiodic clocks allow organisms to predict the coming season. In insects, the seasonal adaptive response mainly takes the form of diapause. The extensively studied photoperiodic clock in insects was primarily characterized by a “black-box” approach, resulting in numerous cybernetic models. This is in contrast with the circadian clock, which has been dissected pragmatically at the molecular level, particularly in Drosophila. Unfortunately, Drosophila melanogaster, the favorite model organism for circadian studies, does not demonstrate a pronounced seasonal response, and consequently molecular analysis has not progressed in this area. In the current article, the authors explore different ways in which identified molecular components of the circadian pacemaker may play a role in photoperiodism. Future progress in understanding the Drosophilacircadian pacemaker, particularly as further output components are identified, may provide a direct link between the clock and photoperiodism. In addition, with improved molecular tools, it is now possible to turn to other insects that have a more dramatic photoperiodic response.
Testicular Apoptosis Is Down-Regulated during Spontaneous Recrudescence in White-Footed Mice (Peromyscus leucopus)
Authors: Young Kelly A. , Zirkin Barry R. , Nelson Randy J.
Published: May 2004

Among individuals of many nontropical species, seasonal breeding is timed by tracking changes in the daily photoperiod. Transfer of rodents to short (< 12 h of light/day) day lengths for 6 to 14 weeks can induce regression of the testes mediated by apoptosis. After 16 to 20 weeks of short day exposure, reproductive function is “spontaneously” initiated, and testicular recrudescence is observed. The gonadal mechanisms that underlie testicular recrudescence are not fully understood. If the onset of testicular regrowth that occursduring spontaneous recrudescence reflects a down-regulation of apoptotic signals, then a decline in apoptosis should be noted concurrent with increased testis mass. This experiment sought toassess the role of apoptosis in the restoration of reproductive capacity to photoperiod-inhibited white-footed mice. Males were assigned to long (16:8 LD) or short (8:16 LD) photoperiods for0, 14, 18, 22, 26, or 30 weeks. At each of these time points, testis mass and testosterone concentrations were assessed. In addition, apoptotic activity was measured using both in situ terminal deoxynucleotidyl transferase dNTP end labeling (TUNEL) and DNAladdering. Short photoperiod exposure induced maximal decreases in testicular parameters after 14 weeks ( p <0.05). After 26 weeks of short days, testis mass was no longer different between males housed in long days and those housed in short days. In contrast, the high incidence of apoptotic TUNEL labeling and DNAladdering observed at 14 weeks was reduced to long day values after 22 weeks ofshort day exposure. Together, our results establish that a decrease in testicular apoptosis coincides with testicular recrudescence in white-footed mice. The current study demonstrates a decline in the incidence of testicular cell death concomitant with changes in testis mass or length, elucidating a timeline of changes at the cellular level related to the onset of recrudescence.
Getting Through to Circadian Oscillators: Why Use Constant Routines?
Authors: Duffy Jeanne F. , Dijk Derk-Jan
Published: May 2004

Overt 24-h rhythmicity is composed of both exogenous and endogenous components, reflecting the product of multiple (periodic) feedback loops with a core pacemaker at their center. Researchers attempting to reveal the endogenous circadian (near 24-h) component of rhythms commonly conduct their experiments under constant environmental conditions. However, even under constant environmental conditions, rhythmic changes in behavior, such as food intake or the sleep-wake cycle, can contribute to observed rhythmicity in many physiological and endocrine variables. Assessment of characteristics of the core circadian pacemaker and its direct contribution to rhythmicity in different variables, including rhythmicity in gene expression, may be more reliable when such periodic behaviors are eliminated or kept constant across all circadian phases. This is relevant for the assessment of the status of the circadian pacemaker in situations in which the sleep-wake cycle or food intake regimes are altered because of external conditions, such as in shift work or jet lag. It is also relevant for situations in which differences in overt rhythmicity could be due to changes in either sleep oscillatory processes or circadian rhythmicity, such as advanced or delayed sleep phase syndromes, in aging, or in particular clinical conditions. Researchers studying human circadian rhythms have developed constant routine protocols to assess the status of the circadian pacemaker in constant behavioral and environmental conditions, whereas this technique is often thought to be unnecessary in the study of animal rhythms. In this short review, the authors summarize constant routine methodology and what has been learned from constant routines and argue that animal and human circadian rhythm researchers should (continue to) use constant routines as a step on the road to getting through to central and peripheral circadian oscillators in the intact organism.
Photoperiod, Reproduction, and Immunity in Select Strains of Inbred Mice
Authors: Yellon S. M. , Tran L. T.
Published: May 2004

The purpose of this study was to determine whether decreased day lengths affect reproduction or the immune system in inbred mice. Irrespective of a nocturnal pineal melatonin rise, the signal for day length information, body and testis weights were the same in various strains 8 weeks after transfer from long to short days (16 to8hof light/day) compared to mice that remained in long days. Serum testosterone was unaffected by the photoperiod shift. The second goal was to determine whether the shift from long to short days influenced lymphocyte populations in spleen or blood, as well as innate and cell-mediated immune cell functions in C3H/HeN mice, an inbred strain with a robust melatonin rhythm. By flow cytometry, a stable percentage and number of B cells, T cells, and natural killer cells were identified in spleen from mice in both long and short days during the day and night. This complement of immunophenotypes in spleen suggests that equivalent functional capabilities persist in secondary lymphoid tissue of mice irrespective of day length. This was supported by findings that cytolytic activity by splenic natural killer cells (innate immunity) and antigen-induced T cell–dependent B cell antibody production (adaptive immunity) were similar in mice in long and short days. In blood, cell numbers but not helper T cell subset percentages (i.e., naive, memory, cytotoxic, or activated) were augmented in mice in short compared to long days, a consequence of increased circulating B cells. Day length differences in certain immunophenotypes in circulation may forecast photoperiod-mediated alterations in responsiveness to pathogens that are associated with a change in season. At night, the reduced proportion of cytotoxic T cells (long and short days), as well as increases in the percentage of activated T cells (long days), B cells (short days), and NK cell activity (long and short days) relative to daytime, suggests that surveillance and function by select immunophenotypes may adapt to circadian transitions even in highly inbred species. Thus, inbred mice retain capabilities for photoperiod to influence traitspecific aspects of immune cell but not reproductive function.
Bright-Light Mask Treatment of Delayed Sleep Phase Syndrome
Authors: Cole Roger J. , Smith Julian S. , Alcal Yvonne C. , Elliott Jeffrey A. , Kripke Daniel F.
Published: May 2004

We treated delayed sleep phase syndrome (DSPS) with an illuminated mask that provides light through closed eyelids during sleep. Volunteers received either bright white light (2,700 lux, n = 28) or dim red light placebo (0.1 lux, n = 26) for 26 days at home. Mask lights were turned on (< 0.01 lux) 4 h before arising, ramped up for 1 h, and remained on at full brightness until arising. Volunteers also attempted to systematically advance sleep time, avoid naps, and avoid evening bright light. The light mask was well tolerated and produced little sleep disturbance. The acrophase of urinary 6-sulphatoxymelatonin (6-SMT) excretion advanced significantly from baseline in the bright group ( p < 0.0006) and not in the dim group, but final phases were not significantly earlier in the bright group (ANCOVA ns). Bright treatment did produce significantly earlier phases, however, among volunteers whose baseline 6-SMT acrophase was later than the median of 0602 h (bright shift: 0732-0554 h, p < 0.0009; dim shift: 0746-0717 h, ns; ANCOVA p = 0.03). In this subgroup, sleep onset advanced significantly only with bright but not dim treatment (sleep onset shift: bright 0306-0145 h, p < 0.0002; dim 0229-0211 h, ns; ANCOVA p < .05). Despite equal expectations at baseline, participants rated bright treatment as more effective than dim treatment ( p < 0.04). We conclude that bright-light mask treatment advances circadian phase and provides clinical benefit in DSPS individuals whose initial circadian delay is relatively severe.
Translational and Transcriptional Inhibitors Block Serotonergic Phase Advances of the Suprachiasmatic Nucleus Circadian Pacemaker In Vitro
Authors: Jovanovska Aneta , Prosser Rebecca A.
Published: May 2004

The mammalian circadian pacemaker is located in the suprachiasmatic nucleus (SCN). Various inputs modulate pacemaker phase, including the serotonergic (5HTergic) input from the midbrain raphe. 5HT phase-advances the SCN pacemaker when applied during mid subjective day. In vitro studies indicate that 5HT advances the mammalian circadian pacemaker through a process that includes stimulating 5HT7 receptors, activating protein kinase A, and opening K+ channels. How these cytoplasmic and membrane events translate into a shift in the molecular core of the circadian oscillator is not known. To further understand this process, the authors investigated whether 5HTergic phase advances require transcription or translation. Using two reversible translational inhibitors, anisomycin and cycloheximide, the authors show that inhibiting protein synthesis blocks 5HTergic phase shifts. The authors further show that the transcriptional inhibitor 5,6-dichloro-1-[.beta]-ribobenzimidazole also blocks 5HTergic phase shifts. These results are similar to those found previously with respect to 5HTergic modulation of the Aplysia ocular circadian clock, and suggest that 5HT may phase-shift the SCN pacemaker through increasing transcription and translation of specific proteins.
Is Food Availability a Circannual Zeitgeber in Tropical Birds? A Field Experiment on Stonechats in Tropical Africa
Authors: Scheuerlein Alexander , Gwinner Eberhard
Published: May 2004

Equatorial stonechats ( Saxicola torquata axillaris) in Africa are seasonal breeders like their temperate-zone conspecifics ( S.t. rubicola). Their annual cycle in gonadal size and function is controlled by an endogenous circannual rhythmicity that has been shown to run for up to 10 years in a constant equatorial photoperiod under laboratory conditions, with a period deviating from 12 months. In nature, however, this rhythm is synchronized with the actual year. Because photoperiod is essentially constant at the equator, it is likely that other environmental factors act as zeitgebers. The authors test whether food availability affects reproductive cycles of free-living East African stonechats. The authors offered supplemental food to the birds 2 months before the regular onset of the breeding season. Supplementally fed males started to sing and display earlier than males of control pairs that did not receive extra food. Although the supplemented food advanced the onset of the breeding season in the pairs that were fed, the onset of the postnuptial molt following the breeding season was not correspondingly shifted. Furthermore, in the year following the experiment, all pairs initiated breeding at the same time. The authors conclude that food availability does not act as a zeitgeber, but rather as a factor that modifies the timing of reproduction without affecting the underlying rhythmicity. The authors propose that this is adaptive under environmental conditions that are relatively constant within a given year but may vary considerably between years. The zeitgeber synchronizing the endogenous rhythmicity remains to be identified.
Eventual Entrainment of the Human Circadian Pacemaker by Melatonin is Independent of the Circadian Phase of Treatment Initiation: Clinical Implications
Authors: Lewy Alfred J. , Emens Jonathan S. , Bernert Rebecca A. , Lefler Bryan J.
Published: May 2004

About 15% of the legally blind completely lack light perception. Most of these individuals have abnormally phased circadian rhythms and many free-run. Light treatment is not an option for them. However, melatonin treatment can be highly effective. A daily dose of 0.5 mg of melatonin usually results in entrainment. It has been suggested that treatment in individuals with circadian periods > 24 h should be initiated on the advance zone of the melatonin phase response curve, which was based on findings in which melatonin initiated on the delay zone were less likely to result in entrainment, even though treatment continued across all circadian phases. In the present study, 7 totally blind people started low-dose melatonin treatment (0.5 mg; 1 person was given 0.05 mg) on the delay zone. All entrained as circadian phase free-ran and the advance zone of the melatonin phase response curve coincided with the time of melatonin administration. These results are consistent with studies in other mammals. It does not appear that low-dose melatonin treatment needs to be initiated on the advance zone to induce eventual entrainment in blind people with free-running rhythms > 24 h. Therefore, it is not essential that circadian phase be ascertained before starting low-dose melatonin treatment of blind people.
Temporal Precision in the Mammalian Circadian System: A Reliable Clock from Less Reliable Neurons
Authors: Herzog Erik D. , Aton Sara J. , Numano Rika , Sakaki Yoshiyuki , Tei Hajime
Published: May 2004

The mammalian SCN contains a biological clock that drives remarkably precise circadian rhythms in vivo and in vitro. This study asks whether the cycle-to-cycle variability of behavioral rhythms in mice can be attributed to precision of individual circadian pacemakers within the SCN or their interactions. The authors measured the standard deviation of the cycle-to-cycle period from 7-day recordings of running wheel activity, Period1 gene expression in cultured SCN explants, and firing rate patterns of dispersed SCN neurons. Period variability of the intact tissue and animal was lower than single neurons. The median variability of running wheel and Period1 rhythms was less than 40 min per cycle compared to 2.1 h in firing rate rhythms of dispersed SCN neurons. The most precise SCN neuron, with a period deviation of 1.1 h, was 10 times noisier than the most accurate SCN explant (0.1 h) or mouse (0.1 h) but comparable to the least stable explant (2.1 h) and mouse (1.1 h). This variability correlated with intrinsic period in mice and SCN explants but not with single cells. Precision was unrelated to the amplitude of rhythms and did not change significantly with age up to 1 year after birth. Analysis of the serial correlation of cycle-to-cycle period revealed that approximately half of this variability is attributable to noise outside the pacemaker. These results indicate that cell-cell interactions within the SCN reduce pacemaker noise to determine the precision of circadian rhythms in the tissue and in behavior.
Phase Determination of Circadian Gene Expression in Synechococcus Elongatus PCC 7942
Authors: Min Hongtao , Liu Yi , Johnson Carl H. , Golden Susan S.
Published: May 2004

The authors analyzed the upstream regulatory region of purF, a gene that is expressed in a minority phase that peaks at dawn (class 2 circadian phasing) in Synechococcus elongatus, to determine whether specific cis elements are responsible for this characteristic expression pattern. Fusions of various promoter-bearing fragments to luciferase reporter genes showed that normal class 2 phasing of purF expression was correlated with promoter strength. No specific cis element that is separable from the promoter was responsible for determining phase. Very weak promoter activity of unstable phasing was mapped to a 50-bp segment. Inclusion of sequences that flank this minimal promoter either upstream or downstream increased the promoter strength and stabilized the phase in class 2, but neither segment was individually necessary. Because the data suggested a role for the overall promoter context rather than a specific “phase element,” the authors proposed that DNA topology is important in the phase determination of circadian gene expression in S. elongatus. To test this hypothesis, they fused the well-characterized DNA topology-dependent Escherichia coli fis promoter to luciferase and showed that it acts as a class 2 promoter in S. elongatus.
Plasticity of Circadian Behavior and the Suprachiasmatic Nucleus Following Exposure to Non-24-Hour Light Cycles
Authors: Aton Sara J. , Block Gene D. , Tei Hajime , Yamazaki Shin , Herzog Erik D.
Published: May 2004

Period aftereffects are a form of behavioral plasticity in which the free-running period of circadian behavior undergoes experience-dependent changes. It is unclear whether this plasticity is age dependent and whether the changes in behavioral period relate to changes in the SCN or the retina, 2 known circadian pacemakers in mammals. To determine whether these changes vary with age, Per1-luc transgenic mice (in which the luciferase gene is driven by the Period1 promoter) of different ages were exposed to short (10 h light: 10 h dark, T20) or long (14 h light: 14 h dark, T28) light cycles (T cycles). Recordings of running-wheel activity in constant darkness (DD) revealed that the intrinsic periods of T20 mice were significantly shorter than of T28 mice at all ages. Aftereffects following the shorter light cycle were significantly smaller in mice older than 3 months, corresponding with a decreased ability to entrain to T20. Age did not diminish entrainment or aftereffects in the 28-h light schedule. The behavioral period of pups born in DD depended on the T cycle experienced in utero, showing maternal transference of aftereffects. Recordings of Per1-luc activity from the isolated SCN in vitro revealed that the SCN of young mice expressed aftereffects, but the periods of behavior and SCN were negatively correlated. Enucleation in DD had no effect on behavioral aftereffects, indicating the eyes are not required for aftereffects expression. These data show that circadian aftereffects are an age-dependent form of plasticity mediated by stable changes in the SCN and, importantly, extra-SCN tissues.
Crepuscular Rhythms of EEG Sleep-Wake in a Hystricomorph Rodent, Octodon degus
Authors: Kas Martien J. H. , Edgar Dale M.
Published: May 2004

Sleep-wake circadian rhythms are well documented for nocturnal rodents, but little is known about sleep regulation in diurnal or crepuscular rodent species. This study examined the circadian sleep-wake rhythms in Octodon degus by means of electroencephalogram (EEG) analysis. Recordings were made from animals housed with or without running wheels in the cages. In a 24-h light-dark (LD) cycle (LD 12:12), sleep and wake patterns were highly fragmented under both conditions except for crepuscular timed episodes of waking. Without running wheels, sleep bout lengths averaged 3.7 ± 0.1 min, and total sleep time was 37.6 ± 3.7% per 24 h. Although the percentage of total wakefulness was similar during the light phase (63.4 ± 2.4%) and dark phase (61.5 ± 2.8%), measures of locomotor activity (LMA) and body temperature were generally greater during the day than during the night. Without running wheels, EEG slow wave activity (SWA) in nonrapid eye movement (NREM) sleep exhibited a circadian waveform that was elevated only during the light phase. SWA peaked at Zeitgeber Time 7 (ZT 7) (several hours after the dominant waking episode at ZT 23), then declined across the later half of the light phase and into the dark phase. Voluntary wheel running did not alter daily total sleep time, the duration of average sleep bouts, or maximum sleep bouts, but it increased the episode of waking, LMA, and body temperature at ZTs 11-12. Under these conditions, NREM sleep and SWA exhibited crepuscular patterns, with elevated SWA during the day and night. Although Octodon degus exhibited no strong preference for sleep during the light or dark phase, these data suggest that in this species homeostatic sleep responses (indicated by SWA) are gated by the dominant crepuscular episode(s) of waking and can be influenced by wheel running.
A Parallelism between Human Body Temperature and Performance Independent of the Endogenous Circadian Pacemaker
Authors: Monk Timothy H. , Carrier Julie
Published: May 2004

A battery of performance tests involving manual dexterity, serial search, and verbal reasoning was given about seven times per day to 2 healthy young male subjects (22 and 25 years of age) involved in separate forced desynchrony studies, each involving several months of temporal isolation. In these studies, the period lengths (denoted T) of the imposed day lengths (sleep/wake and light/dark cycles) were 25.8 and 26.0 h for the 2 subjects. For each subject, the endogenous circadian pacemaker (ECP) failed to entrain to a period of T and instead free ran at a period length denoted tau (24.2 and 24.5 h). By educing performance rhythms (and rectal temperature rhythms) separately at tau and at T (after three complete beating cycles for the first subject and two complete beating cycles for the second subject), the hypothesis could be tested as to whether performance and temperature were parallel, both when educed at tau (indicating ECP influence) and when educed at T (indicating sleep/wake cycle influences). The hypothesis was consistently confirmed at tau and mostly confirmed at T. For most variables, when educed at T, both performance speed and body temperature showed an inverted V-shaped function, with a peak about 9 to 12 h after waking.