bluuebunny/crossref_metadata_2025 huggingface dataset:
Internal-External Control, Learning, and Participation in Occupational Education
Authors: Peters John Marshall
Published: March 2007

The objectives were to determine the effect of internal-external control on retention of control-relevant versus noncontrol-relevant- information and to investigate differences among internal and external prison inmates in their participation in occupational edu cation programs. Results of a 2x3 factorially designed experiment supported the thesis that internal subjects retain more information than external subjects. However, that this difference depends on the perceived relevancy of such information to control was not supported by the data. A greater proportion of internal inmates participated in occupational education programs than did external inmates. It was concluded that a person can be described as possessing a generalized expectancy of control or lack of control over his environment, and that this characteristic can affect his willingness to learn information or engage in activities that could reasonably be expected to increase his chances of control over his environment, such as preparation for employability.
Analysis of Bildungsroman Literature as a Research Modality in Adult Education: an Inquiry
Authors: McKenzie Leon
Published: March 2007

The problem addressed concerns the analysis of a specific genre of literature for the purposes of acquiring new knowledge about adult development and learning. Broad interpretations of the meaning of research are contrasted with interpretations of re searchers in education to suggest the empiricist bias of researchers in education. Literary research in terms of character analysis is described and it is suggested that analysis of literature possesses the potential to be an authentic modality of research. A need for further study in the area of developing research principles for the analysis of literature is indicated.
Adult Education Participation and Occupational Achievement: a Regression Analysis
Authors: Cookson Peter S.
Published: March 2007

Most research of adult education participation has focused on the causal antecedent of such participation rather than the factors which, in turn, might be influenced by adult education participation. Utilizing conventional techniques of path analysis, this study is an examination of the possible effects the adult educa tion participation of Mexican-American small businessmen, together with their formal educational attainment and work experience, have on their attitudinal and behavioral patterns of individual modernity, adoption of modern business practices, and their occupational achievement (meaured in terms of net business income). The analysis is based on data collected by interviews with 60 shopkeepers in the three most populous Mexican-American neighborhoods in Chicago during the summer and autumn of 1975. Findings indicated adult education participation contributed directly to higher levels of individual modernity and adoption of modern business practices and, via this latter variable, indirectly to occupational achievement.
Organizational Barriers To the Administration of Correctional Education: an Analysis of a Correc Tional School District
Authors: Mac Neil Pauline
Published: March 2007

A case study of the correctional school district for New Jersey prisons identified a number of organizational barriers to the administration of educational programs in correctional institu tions. The location of the correctional school district within the state departmental structure, the nature of the relationship between the correctional school district and the correctional institu tion, and the effect of this relationship on the functioning of the correctional school district were examined.

The findings suggest that the major organizational barriers to the administration of educa tional programs in correctional institutions are: (1) the correctional institution's prioritization of containment and control over the care and treatment function; (2) the low status of correctional education within the correctional institution; (3) the low decision making autonomy of the cor rectional school district in areas of staff hiring and firing, program implementation and student participation; and (4) the overall marginality of the correctional education unit both within the Department of Education and the individual correctional institution.
Why Social Movements Matter: Adult Education Theory, Cognitive Praxis, and the Creation of Knowledge
Authors: Holford John
Published: March 2007

Although adult education has long been associated with social movements, the relevance of social movement theory has hardly been explored. This stems in part from limitations in the sociological theory of social movements. New paradigms are emerging which provide a basis for theorizing adult education in terms of cognitive processes in social movements. These have general implications for our understanding of adult education's role in society. This paper considers the notion that adult education is itself a "movement." The development of social movement theory is traced, and reasons for its limited impact on adult education theory are explored. A new approach to understanding social movements in terms of "cognitive praxis," is outlined and its implications for adult education discussed.
Our Youth-Our Secondary Schools
Authors: Georgiades William
Published: March 2007

American education has experienced a series of cyclical reform efforts which have been generally heralded by intense criticism, angry exposetype books, and a search for scapegoats. Most of these reforms overlook two factors outside the school which seriously impact the system: Changing social demographics and shifting student enrollment patterns. These social changes call for new approaches in the organization and administration of our schools with the full support of the family and community. Teacher preparation and schooling must focus on liberal education which, in turn, will produce students capable of learning how to learn along with the ability to evaluate life's activities with a growing sense of moral purpose.
Adolescent Coping Style as a Function of Perceived Family Climate
Authors: Shulman Shmuel , Seiffge-Krenke Inge , Samet Naomi
Published: March 2007

The study compares adolescent coping styles across different perceived family climates. Analyses indicated that the perception of family cohesion and organization, combined with respect for individual development, were related to a higher level of functional coping in the adolescent. A sense of lack of family support, or a sense of an over-controlling family climate, was related to a higher level of dysfunctional coping. Adolescent perception of family climate was found to be related to the nature of the task or situation the adolescent encounters. Findings are discussed in terms of the interface between adolescent development and perception of family processes.
Correlates of Computer Anxiety of Adolescent Students
Authors: Campbell N. Jo
Published: March 2007

Selected correlates of computer anxiety of 1075 male and female students in grades 5 and 12 were investigated using a short form of the Computer Anxiety Scale developed by Newman and Clure (1984). The results of separate multiple regression analyses for the two sexes indicated that five independent variables, perceived effect of computer ability on interpersonal relationships, fear of computer hardware, availability of a computer in the home, perceived relationship between math and computer abilities, and perception of computer ability as related to gender were significant predictors of computer anxiety for both males and females. Availability of a computer at school also entered the multiple regression equation as a significant predictor for females. Perceived effect of computer ability on interpersonal relationships was the best predictor of computer anxiety for both males and females. The results of two three-way analyses of variance indicated no significant sex and grade differences in adolescents' computer anxiety, but significant main effects of use of a computer at school and availability of a computer at home were identified in the analyses.
Chinese-American Adolescents' Reasoning about Cultural Conflicts
Authors: Yau Jenny , Smetana Judith G.
Published: March 2007

This study examined Chinese-American adolescents' reasoning and judgments about cultural issues that cause conflicts with parents. Subjects were 38 Chinese-American adolescents (18 in early adolescence and 20 in late adolescence) varying in acculturation, as assessed by the Y Ying Biculturality Scale. Adolescents responded to two stories involving conflicts between parents' conventional demands for obedience and adolescents' desires for personal jurisdiction. For each story, adolescents judged and justified acts in four conditions that varied the salience of conventional and personal concerns. The results showed that across conditions, responses to the two stories were predominately conventional, but over 50% of responses entailed a recognition of both personal and conventional concerns. Overall, early adolescents used more conventional and pragmatic justifications, whereas late adolescents used more psychological justifications. Adolescents'judgments and reasoning did not differ consistently according to acculturation. The impact of Chinese culture and implications of intraindividual conflict on Chinese-American adolescents'development are discussed.
The Method and Meaning of Emotional Expression and Experience during Adolescence
Authors: Flannery Daniel J. , Torquati Julia C. , Lindemeier LeAnn
Published: March 2007

This review provides an overview of research on emotional expression and emotional experience during adolescence, defined as the period between the ages of 10 and 21 years. Methodological issues related to research on affect in adolescence are reviewed. This is followed by a review of research in two major content areas: (a) biological influences on emotional expression and experience; and (b) emotion in the family. The section on biological influences includes the hormone-affect relationship and the effects of pubertal status and timing. Emotion in the family includes research on attachment, acceptance and warmth, and research on emotional expression and experience. The review concludes with a brief summary of consistentfindings and suggestionsforfuture research.
Gender Differences in Adolescents' Reactions to the Murder of Their Teacher
Authors: Dyregrov Atle , Kristoffersen Jakob Inge , Matthiesen Stig Berge , Mitchell Jeffrey T.
Published: March 2007

One month following the murder of their teacher, 63 adolescents responded to a questionnaire concerning different aspects of the event. Those adolescents who learned about the murderfrom siblings andfriends reported sufferingfrom more intrusive images and depressive thoughts than those adolescents who learned about the event from parents. Girls reported reacting more strongly and talking more with both theirfriends and their parents about the event than did boys. Differing explanations regarding the observed gender differences are suggested Correlations in the data indicate that those students who reported being the most depressed and anxious were those who talked with their friends about the event. Talking with one's parents was associated with less depressive thinking and less avoidance.
Identity Processes
Authors: Grotevant Harold D.
Published: March 2007

In this article, the Kerpelman, Pittnan, and Lamke (1997) microprocess perspective on identity development is discussed. Comments focus on the role of individual differences and cultural and historical contexts in the model, and questions are raised about the ways in which the model conceptualizes and handles developmental shifts in identity.
Exploration of Substance Use Among Lesbian, Gay, and Bisexual Youth
Authors: Rosario Margaret , Hunter Joyce , Gwadz Marya
Published: March 2007

The prevalence and correlates of substance use and abuse were explored among lesbian, gay male, and bisexual youth recruitedfrom gay-focused organizations in New York City. Lifetime substance use was prevalent andfrequent, as was quantity of use and substance abuse symptoms. Few significant gender or ethnic differences emerged, but the significant differences unexpectedly indicated that the female youth were at greater risk for substance abuse than the male youth. Number of substances ever used and substance abuse symptoms were associated with initiating alcohol and illicit drugs to cope with psychological issues. Howeve, number of substances ever used and substance abuse symptoms were not explained by social learning theory, social control theory, or self-derogation theory when relations were explored. Thefindings are interpretedfrom the perspective of sexual identity, specifically that gay, lesbian, and bisexual youth may use substances to cope with the societal stigma of homosexuality.
The Adolescent Risk-Taking Questionnaire
Authors: Gullone Eleonora , Moore Susan , Moss Simon , Boyd Candice
Published: March 2007

Compared to other life periods, adolescence is characterized by a heightened potential for risky behaviors. This study reports the systematic development and psychometric evaluation of a comprehensive Adolescent Risk-Taking Questionnaire (ARQ). It was developed using reports of 570 adolescents and was psychometrically evaluated with a sample of 925 adolescents between 11 and 18 years of age. Principal components analyses yielded a four-factor risk structure, and these factors were substantiated via a confirmatory factor analysis. One week test-retest and internal consistency indices were demonstrated to be sound. Age and gender differences were found to be consistent with reported trends in accident data. Older adolescents and boys reported lower risk perceptions and a higher frequency of risky behaviors than younger adolescents and girls, respectively, supporting the validity of the ARQ. Furthermore, consistent with past research, perceiving higher levels of risk typically related to lower levels of engaging in the respective behaviors.
Relations among Single Mothers’ Awareness of their Adolescents’ Stressors, Maternal Monitoring, Mother-Adolescent Communication, and Adolescent Adjustment
Authors: Hartos Jessica L. , Power Thomas G.
Published: March 2007

The goal of this study was to examine the relations among mothers’ awareness of their adolescents’ stressors, mother-adolescent communication, maternal monitoring, and adolescent adjustment in single-parent families. Measures of adolescent stress, communication, monitoring, and adolescents’ anxious/depressed and aggressive behaviors were completed by 82 adolescents and their single mothers. The findings indicated that single mothers were aware of about half of their adolescents’ stressors and not as aware of the importance to their adolescents. Adolescents in the group characterized by high stress/low agreement reported more problem behaviors. Moreover, monitoring mediated the relationship between awareness group membership and adolescent adjustment as high agreement groups reported more monitoring and fewer problem behaviors than did low agreement groups. Thus, during early adolescence when adolescent stress increases and family communication and monitoring change, monitoring by single mothers may increase awareness of adolescent stress, which in turn may buffer the negative effects of stress on adolescent adjustment.
Attachment Cognitions Predict Perceived and Enacted Social Support during Late Adolescence
Authors: Herzberg David S. , Hammen Constance , Burge Dorli , Daley Shannon E. , Davila Joanne , Lindberg Nangel
Published: March 2007

This study examined the relationship between attachment cognitions and social support in a community sample of late-adolescent women. Participants were 129 women recruited as seniors from three Los Angeles high schools to take part in a 5-year longitudinal study of adolescent development. As predicted, attachment cognitions representing greater security in close relationships were found to be associated with higher levels of perceived and enacted social support. The study also found that differences between subjects reporting secure and insecure attachment cognitions were primarily in the domain of enacted emotional support, as opposed to two other types of enacted support, information and material aid. These findings are consistent with a basic principle of attachment theory: that internalized representations of attachment relationships continue to influence interpersonal functioning during adolescent and adult development.
Circadian Participation in the Photoregulation of Testis Activity and Prolactin Secretion in the Mink, a Short-Day Breeder
Authors: Boissin-Agasse L. , Jacquet J.M. , Lacroix A. , Boissin J.
Published: March 2007

It has been demonstrated that an endogenous mechanism is involved in photoperiodic time measurement in the mink, a short-day-breeding mannal. A study of testicular activity (testicular volume, plasma testosterone concentration) and plasma prolactin level was carried out in sexually resting minks (the experiment began in November). Groups of minks were kept in the natural photoperiod or subjected to different resonance light-dark (LD) cycles (LD 4:8, LD 4:20, LD 4:32, LD 4:44); an additional group of animals was reared in an ahemeral photoperiod (LD 4:16). A rapid increase of testicular activity was observed in control animals or those kept in LD 4:20 (T 24) and LD 4:44 (T 48). In the other groups of animals, those kept in LD 4:8 (T 12), LD 4:32 (T 36), and LD 4:16 (T 20), testicular function remained at rest. Prolactin secretion was, in contrast, stimulated in the groups kept in LD 4:8 (T 12). LD 4:32 (T 36), and LD 4:16 (T 20), and remained low in the groups kept in LD 4:20 (T 24) and LD 4:44 (T 48). These results show that the effects of the different photoperiodic regimens do not depend on the duration of the photophase, but rather on the period of the LD cycles. The LD cycles that allow an increase of testicular function are those that are inhibitory to repro duction in birds and long-day-breeding mammals. To explain these results, it is suggested that in the mink exposure to light during the circadian photosensitive phase induces inhibition of testicular activity and stimulation of prolactin secretion. To explain the opposite effects of a single photoperiod on testicular function and secretion of prolactin, the hypothesis has been advanced that, in the mink, long days might simultaneously inhibit hypothalamic luteinizing- hormone-releasing hormone (LH-RH) activity and prolactin-inhibiting factor (PIF) activity.
Circannual Rhythms of Ground Squirrels: A Test of the Frequency Demultiplication Hypothesis
Authors: Carmichael Marie S. , Zucker Irving
Published: March 2007

The frequency demultiplication hypothesis (FDH) posits that circannual rhythms are generated from circadian cycles by frequency transformation to the lower-frequency rhythm. To test the FDH, we determined the periods of the circannual body mass and estrous cycles of golden-mantled ground squirrels with circadian locomotor activity rhythms entrained to 23-, 24-, or 25-hr days (T-cycles). Circannual period length did not differ among squirrels entrained to the different T-cycles; intergroup ranges were 298-314 days and 303-312 days, respectively, for body mass and estrus. These results are not consistent with the FDH and suggest instead that separate mechanisms generate circadian and circannual rhythms. In ground squirrels the circannual system influences circadian organization, but a reciprocal influence of circadian on circannual rhythms has yet to be demonstrated.
Circannual Variations in Plasma Luteinizing Hormone Levels in Castrated Male European Starlings (Sturnus vulgaris)
Authors: Dittami John , Gwinner Eberhard
Published: March 2007

Intact and castrated male European starlings were held for about 2 years in a constant 12-hr photoperiod and constant temperature conditions. At 1- to 2-month intervals, testicular width was measured by laparotomy, and blood samples were taken for analysis of plasma luteinizing hormone (LH). Most of the control birds went through at least one circannual cycle of testicular width and plasma LH concentration. In the castrates, a similar proportion of birds went through circannual LH cycles with periods indistinguishable from those of the controls. It is concluded that the testes and their hormones are not essential components of the mechanism that generates circannual gonadal cycles in male European starlings.
Two Circadian Rhythms in Pairs of Sparrows
Authors: Binkley Sue , Mosher Karen
Published: March 2007

Circadian rhythms of perch-hopping activity were recorded for over 200 days from pairs of house sparrows (Passer domesticus) kept in the same cage and treated with a light- dark cycle (LD 12:12), with constant light (LL), and with constant dark (DD). Most pairs entrained to the LD 12:12 cycle and exhibited free-running circadian rhythms in LL and DD. Two rhythms were visible in the records of 40% of the pairs in DD and in 50% of the pairs in LL. Otherwise, free-running pairs displayed a single circadian rhythm of perching activity.
The Visual Input Stage of the Mammalian Circadian Pacemaking System: II. The Effect of Light and Drugs on Retinal Function
Authors: Terman Michael , Remé Charlotte E. , Wirz-Justice Anna
Published: March 2007

Acute light pulses as well as long-term light exposure may not only modulate photoreceptive properties, but also induce reversible or irreversible damage to the retina, depending on exposure conditions. Illuminance levels in laboratory animal colonies and manipulations of lighting regimens in circadian rhythm research can threaten retinal structure and physiology, and may therefore modify zeitgeber input to the central circadian system. Given the opportunity to escape light at any time, the nocturnal rat self-selects a seasonally varying "naturalistic skeleton photoperiod" that protects the eyes from potential damage by nonphysiological light exposures. Both rod outer-segment disk shedding and behavioral circadian phase shifts are elicited by low levels of twilight stimulation. From this vantage point, we hypothesize that certain basic properties of circadian rhythms (e.g., Aschoff's rule and splitting) may reflect modulation of retinal physiology by light. Pharmacological manipulations with or without the addition of lighting strategies have been used to analyze the neurochemistry of circadian timekeeping. Drug modulation of light input at the level of the retina may add to or interact with direct drug modulation of the central circadian pacemaking system.
Circadian Inputs Influence the Performance of a Spiking, Movement-Sensitive Neuron in the Visual System of the Blowfly
Authors: Bult R. , Schuling F.H. , Mastebroek H.A.K.
Published: March 2007

Long-term extracellular recordings from a spiking, movement-sensitive giant neuron (H1) in the third optic ganglion of the blowfly Calliphora vicina (L.) revealed periodic endogenous sensitivity fluctuations. The sensitivity changes showed properties typical of an endogenous circadian rhythm. This was true for the responses in reaction to intensity changes of visual patterns as well as for the responses elicited by pattern movement. For these two types of stimuli, the circadian fluctuations were comparable, but the envelope in the case of responses to movement was more robust. A circadian fluctuation in responses to movement is, therefore, present at the level of single elementary movement detectors.

The tonic activity of the neuron was also shown to be under circadian control. In constant darkness (DD) the fluctuation was circadian, whereas in constant light it was not. The subjective light-dark (LD) transitions in the tonic activity in DD closely followed the LD transitions in the holding cages initially; that is, there was low activity at night and high activity during the daytime. The sensitivity fluctuations in response to visual stimuli led the tonic spike activity fluctuations by several hours.
Nonphotic Phase Shifting in Hamster Clock Mutants
Authors: Mrosovsky N. , Salmon Peggy A. , Menaker Michael , Ralph Martin R.
Published: March 2007

Golden hamsters with the tau mutation were kept in the dark and induced to become active through confinement to a novel running wheel for 3 hr. The response of the mutants to this nonphotic phase-shifting stimulus differed from that of wild-type hamsters. The mutants showed larger phase shifts, and their phase response curves differed in shape, with an advance portion at about circadian time 24, a phase at which wild types show delays. The results establish that the tau mutation, in addition to its already known effects, alters the response of the circadian system to nonphotic events.
NMDA as Well as Non-NMDA Receptor Antagonists Can Prevent the Phase-Shifting Effects of Light on the Circadian System of the Golden Hamster
Authors: Colwell Christopher S. , Menaker Michael
Published: March 2007

The present experiments were designed to evaluate whether the intraventricular administration of excitatory amino acid (EAA) receptor antagonists would prevent light-induced phase shifts of the circadian rhythm of wheel-running activity in the hamster. Administration of the non- N-methyl-D-aspartate (non-NMDA) antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) blocked light-induced phase advances and delays. Similarly, administration of the competitive NMDA receptor antagonist, 3(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), prevented light-induced phase advances and delays. Neither drug by itself caused any consistent effect on the phase of the rhythm. These data provide further evidence that EAA receptors mediate the effects of light on the circadian system, and suggest that both NMDA and non-NMDA receptor types may be involved.
Behavior in Light-Dark Cycles of Drosophila Mutants That Are Arrhythmic, Blind, or Both
Authors: Wheeler David A. , Hamblen-Coyle Melanie J. , Dushay Mitchell S. , Hall Jeffrey C.
Published: March 2007

Certain of the rhythm mutations in Drosophila melanogaster lead to arrhythmic locomotor activity (and aperiodic eclosion) in constant conditions. In light-dark (LD) cycles, however, such mutants exhibit clear fluctuations between high levels of activity when the lights are on and much lower ones when they are off. Our data, in contrast to some previous conclusions, strongly suggest that period0 ( per0) adults are, in LD conditions, merely being "forced" into exhibiting periodic behavior. These experiments involved application of 8-, 12-, 16-, and 24-hr LD cycles, in which the arrhythmic mutant could have any of these periodicities imposed upon it, whereas wild-type flies tended to exhibit periods of about 24 hr in cycling conditions whose T values were >8 hr different from 24. In phase-shift experiments, it was found that Drosophila expressing genotypes associated with rhythmicity achieved a 5-hr advance over a 2-day period following an advanced lights-on; per0 adults altered the phase of their locomotor peaks more rapidly. Against a background of the fact that eyeless or blind flies exhibit normal entrainment, it was hypothesized that double-mutant flies— carrying such visual mutations and per0 as well—should not synchronize to LD cycles, if the forced rhythms seen in the latter single-mutant type are mediated solely by light input through the external photoreceptors. Since an appreciable proportion of the double mutants did synchronize (to LD 12:12), it is thus suggested that the visual cues involved in forcing rhythmicity could be input through the same extraocular photoreceptors that, in general, subserve the fly's rhythm system.
Winter Adaptations of Male Deer Mice (Peromyscus maniculatus ) and Prairie Voles (Microtus ochrogaster) That Vary in Reproductive Responsiveness to Photoperiod
Authors: Moffatt Christopher A. , DeVries A. Courtney , Nelson Randy J.
Published: March 2007

Individuals of many nontropical rodent species restrict breeding to the spring and summer. Seasonal reproductive quiescence putatively reflects the energetic incompatibility of breeding and thermoregulatory activities. However, so-called "out-of-season" breeding occurs in virtually all rodent populations examined, suggesting that the incompatibility can be resolved. Both reproductive inhibition and development of energy-saving adaptations are mediated by environmental photoperiod, but some individuals do not inhibit reproduction in short days. In order to assess the costs and benefits of winter breeding, the present study examined the extent to which male prairie voles ( Microtus ochrogaster) and deer mice ( Peromyscus maniculatus) that maintained summer reproductive function in winter-simulated daylengths also maintained summer thermoregulatory adaptations. Circadian locomotor activity patterns, basal metabolic rate, capacity for nonshivering thermogenesis, nest building, body mass, and daily food consumption were compared among short-day (LD 8:16) regressed males, short-day (LD 8:16) nonregressed males, and long-day (LD 16:8) males. Short-day nonregressed deer mice resembled long-day conspecifics in terms of body mass and nest-building activities; however, the locomotor activity pattern of short-day nonregressed deer mice was similar to that of their short-day regressed conspecifics. Short-day nonregressed prairie voles had body masses similar to those of long-day conspecifics. Regardless of their reproductive response to photoperiod, short-day prairie voles reduced their daily food consumption and wheel-running activity, compared to long-day voles. These results suggest that winter breeding has energetic costs, most likely resulting from maintaining a "summer-like" body mass relative to that of reproductively regressed animals. These costs may be ameliorated to some extent by the reduction in locomotor activity and nest-building behavior emitted by short-day animals, regardless of reproductive response to short days. Thus, the occurrence of winter breeding may be the result of sufficient numbers of reproductively photoperiod-nonresponsive morphs in the population and sufficiently mild ambient conditions to permit survival of these larger animals.
Calmodulin Inhibitors Produce Phase Shifts of Circadian Rhythms In Vivo and In Vitro
Authors: Shibata Shigenobu , Moore Robert Y.
Published: March 2007

The effect of calmodulin inibitors on the circadian rhythm of locomotor activity and on the rhythm of suprachiasmatic nuclear (SCN) neuron firing rate recorded in vitro from hypothalamic slices was examined. Trifluoperazine produces changes in a dose-dependent manner in the phase of the activity rhythm, with phase advances throughout most of the subjective day extending into the subjec tive night. These phase changes in the activity rhythm occur rapidly and without induction of locomotor activity at the time of treatment. Similarly, trifluoperazine and the naphthalenesulfonamide W-7 produce changes in phase delays in the subjective night extending into early subjective day. The effects are greater with respect to amplitude when measured acutely after treatment than in the next cycle, and both the acute and next-day effects are greater than those observed in vivo, indicating that data from in vitro studies need to be interpreted with caution. These observations indicate that calmodulin inhibitors affect rhythms directly in vivo by altering SCN neuron pacemaker function, as this reflects involvement of calcium-calmodulin binding with activation of a calmodulin-dependent kinase, either to alter intracellular cAMP levels or to alter gene expression directly to modulate the phase of the SCN clock.
Differential Photoperiodic Control of Seasonal Variations in Pulsatile Luteinizing Hormone Release in Long-Day (Ferret) and Short-Day (Mink) Mammals
Authors: Jallageas Monique , Boissin Jean , Mas Nicole
Published: March 2007

The aim of this study was to elucidate the pituitary adjustments implicated in photoperiodic control of reproduction in two mammalian species, the ferret and the mink. In the ferret, which displays renewed testicular activity when the days lengthen, we observed a stimulation of the pulsatile liberation of luteinizing hormone (LH) reflecting the pulsatile activity of the gonadotropin-releasing hormone (GnRH) system when daylight was equal to or in excess of LD 8:16. This photoperiod coincides precisely with the phase of photosensitivity known to be essential for gonadal stimulation in this species. In the mink, which displays renewed testicular activity when the days shorten, pituitary stimulation was activated when daylight was reduced to LD 11:13, and gonadal stimulation occurred only when daylight was further reduced to LD 10:14. In addition to requiring different photoperiodic stimuli to trigger the seasonal reproductive process, the two species display variations in the "timing" of pituitary control of renewed gonadal activity.
Phase-Amplitude Resetting of the Human Circadian Pacemaker via Bright Light: A Further Analysis
Authors: Jewett Megan E. , Kronauer Richard E. , Czeisler Charles A.
Published: March 2007

We present here an analysis of strong, weak, and critical bright-light resetting trials in humans, and report not only phase but also amplitude data for the first time. For this analysis, an appropriate iterative smoothing procedure for phase transition curves is introduced, in which the data are sequenced so as to minimize the perpendicular distance from the data to the smoothed fit. From these smoothed data, we create polar phase-amplitude resetting maps (PARMs) in order to fully illustrate the effects of the resetting stimuli on both circadian amplitude and phase, and thereby to determine whether these resetting results can be decribed by a phase-only model or whether a phase-amplitude model is required. Our results indicate that a single 5-hr episode of bright light induces weak type 1 resetting of the human circadian pacemaker. Two cycles of exposure to the same stimulus on consecutive days induce critical resetting, in which significant amplitude reduction may be observed. A three-cycle stimulus induces strong type 0 resetting with different effects on circadian amplitude, depending on the initial phase of the stimulus application. When a three-cycle stimulus is centered near the nadir of the temperature cycle, large phase shifts are achieved via amplitude suppression. However, when this stimulus is centered away from the temperature nadir, smaller phase shifts are achieved in which both small increases and small decreases in circadian amplitude are observed. These data indicate that the human circadian pacemaker is not a simple, phase-only oscillator. Instead, a full description of human circadian resetting responses to light requires analysis of both phase and amplitude data—a finding that is consistent with a phase-amplitude model of the circadian resetting mechanism.
Circadian Rhythm of Body Temperature in an Ectotherm (Iguana iguana
Authors: Tosini Gianluca , Menaker Michael
Published: March 2007

Ectothermic animals regulate their body temperatures primarily by behavioral adjustment in relation to the thermal characteristics of the environment. Several studies have shown that some vertebrate ectotherms may show a daily pattern of body temperature selection when given a choice of environmental temperature. The pattern of body temperature selection free-runs when the animals are kept in constant darkness, demonstrating the existence of circadian regulation. To test whether there might also be a low amplitude circadian rhythm of body temperature itself, we examined the pattern of body temperature and locomotor activity of the lizard Iguana iguana held in a constant environmental temperature. Both variables were recorded for 3 days in a light:dark cycle and then for 10 days in constant dim light (0.1 lux). Under these conditions the body temperature of the lizard oscillates with a circadian period as does the locomotor behavior. These results demonstrate for the first time that ectothermic animals may display physiologically generated circadian rhythms of body temperature similar to those recorded in endotherms. In some animals the circadian rhythms of body temperature and locomotor activity showed different free-running periods, demonstrating that the body temperature rhythm was not caused by locomotor activity and suggesting internal desyncronization of the two rhythms.
The Use of a Reversible Transcription Inhibitor, DRB, to Investigate the Involvement of Specific Proteins in the Ocular Circadian System of Aplysia
Authors: Koumenis Constantinos , Tran Quang , Eskin Arnold
Published: March 2007

Previously, the effects of 2-h treatments with the reversible transcription inhibitor 5,6-dichloro-1-β-D-ribobenzimidazole (DRB) on the phase of the circadian rhythm in the eye of Aplysia californica were studied. Here we report a study of the effects of DRB on protein synthesis and a more detailed investigation of the effects of DRB on the phase of the circadian rhythm. Treatments of DRB for 30 min reduced the rate of transcription to about 30% of control values, and this inhibition reversed completely within 2 h after the end of the treatment. A phase-response curve was obtained for 30-min treatments of DRB. Shorter (30 min) treatments with DRB produced phase shifts comparable to those produced by treatments with DRB for 2 h. The phase-response curve obtained using 30-min treatments of DRB was similar to one obtained using 2-h treatments with respect to the phase at which DRB exerts its maximum effect on the rhythm (around circadian time [CT] 6). However, some aspects of the two phase-response curves were different. The effect of DRB on the phase of the rhythm appeared rapidly after removal of DRB treatments given during CT 22-6, but the effects of DRB on the phase of the rhythm appeared more slowly (∼10 h) after the treatments given during CT 6-12. Because the effects of DRB on the phase of the overt rhythm appear to be rapid at a particular phase, it is very likely that DRB affects the phase of the rhythm by altering the synthesis of proteins during or shortly after the treatment. Thus we searched for proteins whose synthesis was altered by DRB. Incorporation of labeled amino acids into 2 proteins was found to be altered during the DRB treatment, whereas 15 proteins were affected after the DRB treatment. Among the proteins affected during or shortly after the DRB treatment were four previously identified proteins affected by other treatments that can shift the phase of the eye circadian rhythm. These four proteins are worthy of further study as possible candidates for components of the circadian oscillator.
Chemical and Behavioral Stimulation from Females Accelerates Recrudescence in Male Syrian Hamsters Exposed to Short Days
Authors: Honrado Gerry I. , Fleming Alison S.
Published: March 2007

Interaction with female hamsters maintained under long photoperiods (LP) accelerates behavioral recrudescence in short photoperiod (SP) males. In this experiment, the authors investigated the effects of various types of female sociosexual cues on different measures of reproductive recrudescence in the male. Five groups of SP males were exposed to different female cues for 3 weeks (Weeks 12 to 15). At Week 16, males were allowed to interact with estrus females; behavioral, physiological, and fecundity measures were monitored. The results show that all measures responded in a pseudo-dose-dependent manner to the different female cues presented. SP males not exposed to any female cues and those exposed to distal visual, auditory, and volatile pheromonal cues from estrus females did not copulate, deposit sperm, or impregnate estrus females presented to them at Week 16. SP males allowed direct access to the bedding of estrus females showed marked improvements on these same reproductive measures by Week 16. However, SP males that interacted with LP females between Weeks 12 and 15 showed the greatest level of reproductive function at Week 16. These results show that the type of female sociosexual stimulation is important in accelerating reproductive recrudescence; whereas interaction with LP females may be important in accelerating behavioral recrudescence, both interaction with and exposure to the bedding of LP females may be important in accelerating physiological and reproductive success measures.
Restoration of Circadian Rhythmicity by Transplants of SCN "Micropunches"
Authors: LeSauter Joseph , Lehman Michael N. , Silver Rae
Published: March 2007

Although it is widely accepted that the suprachiasmatic nuclei (SCN) of the hypothalamus serve as biological pacemakers regulating circadian rhythmicity, a number of studies suggest that some circadian rhythms may be controlled by extra-SCN structures. Transplantation of fetal anterior hypothalamic tissue containing the SCN restores circadian locomotor rhythms in SCN-lesioned hosts. Such transplants, however, contain substantial extra-SCN hypothalamic tissue. In the present study, the authors examined the recovery of circadian locomotor rhythms in animals implanted with small grafts harvested by taking "micropunches" from vibratome-sectioned brain slices. Micropunches were taken from three areas of the hypothalamus known to receive retinal input: the SCN, the subparaventricular zone, and the supraoptic nucleus. The results indicate that transplants restricted to the SCN region are necessary and sufficient for restoration of circadian locomotor activity rhythms and that micropunches of tissues from other sources are ineffective.
Disruption of Endocrine Rhythms in Sleeping Sickness With Preserved Relationship Between Hormonal Pulsatility and the REM-NREM Sleep Cycles
Authors: Brandenberger G. , Buguet A. , Spiegel K. , Stanghellini A. , Muanga G. , Bogui P. , Dumas M.
Published: March 2007

In human African trypanosomiasis (sleeping sickness), sleep and wake episodes are sporadically distributed throughout the day and the night. To determine whether these sleep disturbances affect the 24-h hormone profiles and the normal relationships between hormone pulsatility and sleep stages, poly-graphic sleep recordings and concomitant hormone profiles were obtained in 6 African patients with sleeping sickness and in 5 healthy African subjects selected from Abidjan on the Ivory Coast. Polysomnographic recordings were continuous, and blood was taken every 10 min throughout the 24-h period. Plasma was analyzed for cortisol, prolactin, and plasma renin activity (PRA). The 24-h rhythm of cortisol, considered to be an endogenous circadian rhythm, was attenuated in all of the patients except one. However, as in normal subjects, slow wave sleep (SWS) remained associated with the declining phases of the cortisol secretory episodes. Prolactin and PRA profiles, which are strongly influenced by the sleep-wake cycle, did not manifest the nocturnal increase normally associated with the sleep period; instead, they reflected a sporadic distribution of the sleep and wake episodes throughout the 24-h period. In patients with sleeping sickness as in normal subjects, rapid eye movement (REM) sleep began during the descending phases of prolactin pulses. In both groups, PRA reflected the sleep stage distribution with non REM (NREM) sleep occurring during the ascending phases and REM sleep during the descending phases of the PRA oscillations. However, in sleeping sickness patients, the marked sleep fragmentation often did not allow sufficient time for PRA to increase significantly, as is normally the case in subjects with regular NREM-REM sleep cycles. These results demonstrate that, together with the disruption of the sleep-wake cycle, there are profound differences in the temporal organization of the 24-h hormone profiles in humans with African trypanosomiasis. However, the relationship between hormonal pulses and specific sleep stages persists, indicating the existence of a robust link between hormonal release and the internal sleep structure.
Stress-Induced Changes in Circadian Rhythms of Body Temperature and Activity in Rats Are not Caused by Pacemaker Changes
Authors: Meerlo P. , van den Hoofdakker R.H. , Koolhaas J.M. , Daan S.
Published: March 2007

Previous work has shown that social stress in rats (i.e., defeat by an aggressive male conspecific) causes a variety of behavioral and physiological changes including alterations in the daily rhythms of body temperature and activity. To study the role of the circadian pacemaker in these stress-induced changes, three experiments were performed, successively addressing pacemaker period, phase, and sensitivity to light. In all experiments, rats were subjected to social stress by placing them in the home cage of a dominant conspecific for 1 h. This was done on 2 consecutive days, between the second and fifth hours of the activity phase. Experimental animals were attacked by the resident and lost the fight as indicated by submissive behavior. Control animals were placed in an unfamiliar but clean and empty cage for 1 h. In Experiment 1, the effects of social stress on the period of the free-running activity rhythm were studied. Rats were individually housed under constant dim red light. Activity was measured with infrared detectors. Social defeat caused a reduction of activity for a number of days, but the period of the free-running rhythm was not affected. In Experiment 2, the authors studied whether social defeat induced acute phase shifts. Body temperature and activity were measured by means of radiotelemetry with in traperitoneally implanted transmitters. After the social interactions, experimen tal animals were kept under constant dim red light. Social stress caused a profound reduction in the amplitude of the body temperature and activity rhythm, but no significant phase shifts occurred. In Experiment 3, the authors studied whether social defeat affected the circadian pacemaker's sensitivity to light given that the size of light-induced phase shifts is thought to reflect pacemaker amplitude. Again, body temperature and activity were measured by means of telemetry. After double social defeat, animals were kept under continu ous dim red light. One day after the second conflict, animals were subjected to a single 1-h light pulse (300 lux) at circadian time 14. The light pulse induced a phase delay of the body temperature rhythm, but there were no significant differences between the stress and control groups. The data indicate that stress- induced changes in activity and temperature rhythm, as well as behavioral and physiological changes found in earlier experiments, are not caused by changes in the circadian pacemaker. More generally, the data support the notion that overt rhythms are not always a reliable indication of pacemaker function.