bluuebunny/crossref_metadata_2025 huggingface dataset:
Reclaiiming the Concept of Application: From Social to Technological Process and Back Again
Authors: Ottoson Judith M.
Published: March 2007

Application-to put a thing into practical contact with another-is treated variously in adult education as a central concept, vague understanding, or anathema. These mixed responses are tied to the practical roots of application and its tension with science and theory. Technical rationality coopted application to reduce this tension by putting value on outcomes and technology, not on the processes that surround them. By reclaiming application from positivism, new opportunity arises for adult educators to contribute to the applied turn in contemporary theory and practice. In this reconstruction, means connect not only to ends, but to intent; knowledge creation occurs throughout process, not just before it; control surrenders to feasibility and negotiation; individual action interacts with context; and disciplines release control of application to all learners. The complex, multi-dimensional process of application takes more than a good idea. It takes knowledge, skill, endurance, and artistry. To reclaim application is to reclaim the value of process.
Adult Students' Academic and Intellectual Development in College
Authors: Graham Steve , Donaldson Joe F.
Published: March 2007

The ACT College Outcomes Survey was used with a national sample of approximately 28,000 undergraduate students to evaluate the effects of the college environment on academic and intellectual development and to contrast the outcomes for adult learners with those of younger students. Adult and younger students were also compared regarding their involvement and participation in the college environment and a factor analysis was used to identify broad outcome themes deemed important by the adults. The findings show adults were much less involved than younger students in campus activities and much more involved in caring for their families. Despite this lower level of involvement in the college environment, adults reported slightly higher levels of growth than did younger students on most academic and intellectual items. The factor analysis of index scores resulted in five broad intellectual and academic themes including: broadening one's intellectual interests, critical thinking skills, enhancing study skills, career development, and understanding and applying science and technology.
Measuring Social Intimacy in Same-Sex and Opposite-Sex Contexts
Authors: Craig-Bray Laura , Adams Gerald R.
Published: March 2007

A validation study of the social intimacy semi-structured interview, devised by Orlofsky, Marcia and Lesser (1973), was completed to establish predictive validity with self-reported loneliness, psychosocial intimacy capacity, and social interactions in same-sex and opposite-sex contexts. Twenty-three males and 25 females completed the intimacy interview, a loneliness scale, an intimacy scale, and the Rochester Interaction Record. Subjects were categorized using the intimacy interview into isolated, stereotyped and intimate statuses. The evidence suggests both divergence and convergence regarding expectations associated with predictive validity. The interview assessment showed strongest convergence with self-report scales measuring loneliness and intimacy capacity and weakest convergence with social behavior experiences.
Toward an Understanding of Suicide Risks in Young Hispanic Females
Authors: Zayas Luis H.
Published: March 2007

Hispanic adolescents in the United States have been virtually neglected in the literature on youth suicide. Among Hispanic youth, adolescent females constitute a subgroup at risk for depression and suicidal behavior. The author reviews extant literature on adolescent suicide, and discusses such psychosocial and cultural factors as socioeconomic disadvantage, traditional gender-role socialization, acculturation, cultural identity, and intergenerational conflict within the context of suicide attempts among adolescent Hispanic females. It is proposed that the interactive effects of these factors may contribute to suicide attempts among low income, first and second-generation Hispanic adolescent females.
Coping with Stress: A Study of Male Adolescents' Coping Strategies as Related to Adjustment
Authors: Tolor Alexander , Fehon Dwain
Published: March 2007

In an effort to explore the possible relationship between coping strategies and adjustment levels in stressed high school students, 174 male students were first administered the High School Social Readjustment Scale to identify the high stress subjects. High stress individuals were then given a Coping Style Questionnaire and two adjustment measures: the Eysenck Personality Inventory and the Neuroticism Scale Questionnaire in order to establish typical strategies employed in dealing with stress for different adjustment levels. Problem-focused strategies, such as "Taking Positive Action" and "Seeking Information," were the most frequently reported strategies. Comparisons between better and more poorly adjusted students produced only modest relationships with a trend for the former to rely more on active strategies and the latter to rely more on dependent strategies of coping with stress.
Role Transitions and Role Identities during Adolescence: A Symbolic Interactionist View
Authors: Peterson Gary W.
Published: March 2007

The purpose of this paper was to use symbolic interactionist concepts to conceptualize selected issues from the scholarship on pubertal change, parent-youth relationships, peer associations, sexuality, part-time work, and school involvements during adolescence. Based on this examination, the possibility was raised that role involvements and the timing of specific role transitions for the young may influence the extent to which adolescence becomes a stormy or tranquil period. A final issue considered the possibility that identity formation is influenced by the extent to which adolescents are capable of mastering the developmental challenges of roles and role transitions.
Stressful Life Events and Psychiatric Symptoms in Black Adolescent Females
Authors: Brown Lannie J. Pryor , Powell Jack , Earls Felton
Published: March 2007

The relationship between stressful life events andpsychiatric morbidity in a sample of over 1,300 Black adolescent females is reported in this article. The sample was part of a large-scale effort to evaluate primary health services for adolescents in ten United States cities. Black females were considered of special interest since divergent ideas exist regarding their vulnerability to psychiatric problems. On one hand, they are deemed to be at high risk because of their racial and disadvantaged socioeconomic status. A historical legacy exists, however, asserting that Black women acquired coping skills that have permitted them to adapt successfully to such adversities. The hypothesis of this study, that there would be a large group of Black adolescent females with highly stressful experiences and low symptom levels, was not supported by the data. A stronger-than-expected relationship between stress and several types of psychiatric disorders was found. The findings indicated that Black females were not insulated in any special way from the harmful influences of stressful events.
Correlates of Black Adolescent Males' Condom Use
Authors: Pleck Joseph H.
Published: March 2007

In data from the 1979 National Survey of Younger Men, Black adolescent males reported a somewhat lower rate of condom use than did White males at first intercourse. The race difference in condom use was evident only among those becoming sexually active at age 13 years or younger, and when the partner was a steady girlfriend. Black males showed a higher rate of condom use than did White males at most recent intercourse.
Assessing Life Stressors and Social Resources among Adolescents
Authors: Daniels Denise , Moos Rudolf H.
Published: March 2007

A growing body of evidence points to the importance of life stressors and social resources in adolescent functioning. This article describes the Life Stressors and Social Resources Inventory-Youth Form (LISRES-Y), which provides an integrated assessment of life stressors and social resources in eight domains: physical health, home/money, parent, sibling, extended family, school, friend, and boy/girlfriend. The indices were developed on data obtained from four groups of youth: depressed youth, youth with conduct disorder, youth with rheumatic disease, and healthy youth. As expected, depressed youth reported more acute and chronic stressors and fewer social resources than did healthy youth. In addition, the indices were predictably associated with individual differences in depressed mood, anxiety, behavior problems, and self-confidence. Negative life events, ongoing stressors in different domains, and stable social resources all contributed unique variance to the functioning criteria. The findings point to the value of an integrated measure of adolescent life context.
Attitudes toward Consequences of Pregnancy in Young Women Attending a Family Planning Clinic
Authors: Paikoff Roberta L.
Published: March 2007

This study was undertaken to examine the role of female adolescents' anticipation and evaluation of consequences of pregnancy in their sexual behavior and experience. Consequences were operationalized as the degree to which a young woman envisioned discrepant future trajectories due to pregnancy and childbirth in adolescence versus in later adult life. Causal knowledge and attitudes toward consequences of pregnancy as well as contraceptive and pregnancy history were assessed in 78 14-to 20-year-old females at a family platning clinic. Adolescents who had been pregnant anticipated fewer negative consequences of adolescent pregnancy and childbirth than those who were never pregnant. Those who intended to terminate a pregnancy anticipated more negative consequences of adolescent childbirth (but not pregnancy) than those who intended to contitnue a pregnancy. Consistency of contraceptive use was not related to anticipation of negative conisequences of pregnancy or childbirth.
Depressive Experiences of Nonreferred Adolescents and Young Adults
Authors: Moilanen Donna L.
Published: March 2007

The cognitive theory of depression proposed by Beck and the cognitive developmental theory proposed by Piaget provided the theoreticalframeworks for an exploratory and developmentally based investigation of the depressive experiences of nonreferred adolescents and young adults. Specifically, the students'experiences of depressive symptomatology and expressions of hopelessness were examined as a function of their stage of cognitive development (i.e., concrete operations vs. formal operational thought). Participating in the present study were 107 high school, community college, and university students. The students completed several self-report measures designed to assess their levels of depressive symptomatology, hopelessness, and cognitive development. Contrary to theoretical expectations, students classified as functioning within the concrete operational stage were found to report a greater frequency and severity of depressive symptomatology, as well as higher levels of hopelessness, than were those classified within the formal operational stage. The implications and limitations of the study are discussed.
A Microanalytic Method for Exploring Adolescent Emotional Expression
Authors: Safyer Andrew W. , Hauser Stuart T.
Published: March 2007

This article presents a newly constructed observational coding system which assesses emotional expression operationalized through voice cues and speech content. In order to explore its interrater reliability and validity, the coding system is applied to clinical interviews of two groups of young people: psychiatrically hospitalized adolescents and high school students. The subjects are participants in a longitudinal project examining ego development and familial interactions from early adolescence through the later adolescent years. Specific findings demonstrated the differential effects of psychiatric status and gender on emotional expression. Moreover, adolescents'emotion scores were significantly associated with a theoretically related, independent measure-ego development. These findings lend initial supportfor the validity of this coding method. Future directions of the study are also discussed.
The Anatomy of Emotions in Family Therapy with Adolescents
Authors: Liddle Howard A.
Published: March 2007

Emotions in adolescence can be consideredfrom a variety of viewpoints. Although it is not uncommon to address this topic within nonclinical and clinical populations, examination of emotions in adolescence from a treatment or intervention perspective is more unusual. This article discusses the emotions in adolescence literature from the vantage point of a particular, empirically-testedfamily-based intervention model, multidimensionalfamily therapy. Addressing the contemporary challenge to specify how research can influence practice, the article shows how research-based concepts guideformulation of therapeutic strategy, as well as a therapist's in-session behavior. Transcripts with commentaryfrom afamily therapy sessionfocus on a core emotion-relatedproblem with clinical and mtany nonclinical adolescents and their parents-chronic, stable, quick-to-escalate negative emotional exchanges between an adolescent and parent.
The Relationship of Perceived Family Dynamics to Adolescents' Principled Moral Reasoning
Authors: Bakken Linda , Romig Charles
Published: March 2007

There is limited research that addresses the importance offamily factors in the development of principled moral reasoning. To determine whether a relationship indeed existed between family adaptability and cohesion and principled moral reasoning, a sample of 131 middle adolescents was measured on moral reasoning level (using the Defining Issues Test) and levels of perceived family adaptability and cohesion (using Family Adaptability and Cohesion Evaluation Scales). No significant relationships were found between adaptability and the use of principled moral reasoning; however, family cohesion did correlate (but only with males) with percentages of principled moral reasoning. Satisfaction with levels offamily cohesion andfamily adaptability also was significantly related to moral development in males. In addition, there were interaction effects of cohesion and adaptability, suggesting that moderate levels of cohesion, in combination with either high or low levels of adaptability, were related to higher levels of principled moral reasoning.
Taking the Plunge
Authors: Moore Kristin A. , Glei Dana
Published: March 2007

Most research on adolescent development focuses on specific problem behaviors, whereas few studies examine the avoidance of multiple forms of risk taking or the determinants of positive development. This article develops two measures designed to address this lack: (a) a "Missteps Scale" in which multiple forms of risk taking are assessed through the adolescent years, and (b) a "Positive Well-Being Index" that includes multiple measures of positive development, ranging from satisfaction with life to community involvement. Demographic, family, school, and neighborhood characteristics were included in multivariate models estimated on the National Survey of Children. Results indicate that youth who experience fewerfamily disruptions, who are closerwith theirparents, whose parents are better educated, and who hadfewerbehavior problems in elementary school were at lower risk of a misstep and enjoyed greater well-being, net of other variables; whereas children in high-poverty neighborhoods experienced lower well-being and highermisstep hazards. Black youth scored higheron the well-being scale because of their greater religiosity and concernfor correcting social inequalities.
Understanding Intolerance and Multiculturalism
Authors: Camino Linda A.
Published: March 2007

The study of youth development urges a consideration of context, yet rarely are "intolerance" and "multiculturalism" posed as major research variables. This article offers a conceptualframework to identify the daily interpersonal and organizationalprocesses through which intolerance is directed at young people, affecting their exposure to ongoing developmental supports and opportunities. This article draws on data collected from the experiences of individuals attending workshops devoted to multiculturalism and diversity to present three typologies for understanding the processes inherent in subtle, yet powerful, forms of intolerance. These typologies are (a) forms of interpersonal intolerance, (b) fonns of responses to interpersonal intolerance, and (c) forms of organizational orientations to multiculturalism. In the conclusion, research implications of the proposed typologies are discussed in terms of "maps of' phenomena that researchers are likely to discove, and "maps for" thinking about the nature of these forms and the possible ways they might be addressed in future research.
Adolescent Social Networks
Authors: Ennett Susan T. , Bauman Karl E.
Published: March 2007

Peer relationships are considered to be a dominant feature of adolescence, but systematically formed social networks rarely have been studied. A social network analysis was used to describe adolescent friendship patterns and to compare them across schools and time. Ninth graders (n = 1030) atfive high schools identified their friends at Wave 1 and again one year later. The resulting sets offriendship links were subjected to social network analysis. The patterns of linkages identified adolescents as clique members, liaisons, and isolates. Clique membership was the modal social position pattern, but liaisons and isolates also were well represented. The proportions of adolescents representing each socialposition varied across schools. In all samples, cliques were homogeneous in gender, race, and mother's educational level, and cliques were largely stable over a one-year time period. The possibility that social network characteristics could explain a variety of adolescent differences is discussed
Adolescent Girls' Perceptions of Conversations with Mothers and Friends
Authors: Beaumont Sherry L.
Published: March 2007

Early adolescent and middle adolescent girls (N = 56) had discussions with their mothers or close friends. They then listened to sections of their taped conversations and rated themselves and their partners on scales of anxiety, dominance, involvement, andfriendliness. Objective listeners also rated the same conversations. Results indicated that conversations withfniends were rated by girls and outside listeners as more involved and friendly than were conversations with mothers. Girls and their fiends were rated as equally anxious and friendly by both groups of raters, but girls were rated as more anxious and less friendly than their mothers. Early adolescents' conversations with mothers andfriends were rated as equallyfriendly, but middle adolescents'conversations with friends were rated as more friendly than conversations with mothers.
The Relations between Perceived Parental Reciprocity, Perceived Parental Approval, and Adolescent Substance Use
Authors: McMaster Loren E. , Wintre Maxine Gallander
Published: March 2007

The present study examined the additive and interactive associations of 2 parenting variables, Perceived Parental Reciprocity (as measured using the Perception of Parental Reciprocity Scale, POPRS) and Perceived Parental Approval (PPA) of adolescent substance use, with adolescent substance use initiation and escalation. Urban high school students (N = 433) were categorized into abstainers, experimenters, and regular users of alcohol, tobacco, and cannabis. The confirmatory hypotheses thatfrequency ofsubstance use would be associated (a) positively with PPA and (b) negatively with POPRS were supportedfor all 3 substances. The association with POPRS, however, depended on the stage of substance use and the substance in question. The third hypothesis of an interactive association of POPRS and PPA with frequency of substance use was found only for tobacco; however, the direction of the interaction was the reverse of that expected. Implications of thesefindings andfuture directionsfor research are discussed.
A Cross-National Study of Adolescent Peer Concordance on Issues of the Future
Authors: Seltzer Vivian Center , Waterman Richard P.
Published: March 2007

Adolescents in 4 nations were surveyed about theirperceptions regarding adulthood and perceptions they assumed peers to hold. Central tenets of Dynamic Functional Interaction were tested. This theory of adolescent psychological development argues that adolescents try to see themselves in concordance with age-mates to reduce uncertainties associated with transition to adulthood. Approximately 3,500 individuals participated in the cross-national study that explored the association of nationality, age, and gender with level of perceived concordance. Findings disclosed presence of universals as well as national effects. Significant levels of concordance in each nation, at all ages, and in both genders indicated commonalities in the developmental process irrespective of nationality. Scottish youths perceived themselves in concordance with peers almost 50% more often than did U.S. youths. The concordance pattern with respect to age was different markedly in the Philippines. Overall, age and nation had a strongerassociation with concordance than did gender.
Differences in Ethnic Identity in Native American Adolescents as a Function of School Context
Authors: Lysne Mark , Levy Gary D.
Published: March 2007

Examined were differences in ethnic identity in 101 Native American male andfemale 9th and 12th graders. Native American adolescents attending a high school with a predominantly Native American student body demonstrated significantly greater ethnic identity exploration and commitment than Native American adolescents from high schools with a predominantly White student body. The 12th grade Native American adolescentsfrom a high school with a predominantly Native American student body had greater ethnic identity commitment than 9th grade Native American adolescents from the same school. Also, 12th grade Native American adolescents from a high school with a predominantly Native American student body had greater ethnic identity commitment than 9th and 12th grade Native American adolescents from a high school with a predominantly White student body. Exploration and commitnent appear to be important aspects of ethnic identity to Native American adolescents. Results highlight the importance of school and community-based contexts on ethnic identity development in Native American adolescents.
Adolescent School Experiencesand Dropout, Adolescent Pregnancy, and Young Adult Deviant Behavior
Authors: Kasen Stephanie , Cohen Patricia , Brook Judith S.
Published: March 2007

Predictive effects of school experiences were studied over a 7-year interval in a random community sample of 452 adolescents, 12 through 18 years of age. Outcomes examined included dropping out of school, adolescent pregnancy, engaging in criminal activities, criminal conviction, antisocial personality disorder, and alcohol abuse. Logistic regression showed academic achievement, academic aspirations, and leaming-focused school settings to be related to a decline in deviant outcomes independent of the effects of disadvantaged socioeconomic background, low intelligence, childhood conduct problems, and having deviant friends during adolescence. Associations between school conflict and later deviancy were mediated by deviant peer relationships in adolescence and other school characteristics. Prior research reporting continuity of childhood conduct problems and the influence of adolescent affiliations with deviant peers on negative outcomes was supported. Implicationsfor using the school context in riskfactor research and the practical applications of such research for intervention are discussed.
Developmental, Ethnic, and Gender Differences in Ethnic Identity among Adolescents
Authors: Rotheram-Borus Mary Jane , Lightfoot Marguerita , Moraes Anna , Dopkins Steve , LaCour Jean
Published: March 2007

Students' ratings of five components of ethnic identity were examined: their ethnic self-label, reference group, ethnically related attitudes (ethnic pride, separatistfeeling, stereotyping of ethnic groups), values, and social expectations. Each component was examined among 32S African American, Latino, Filipino, and Anglo adolescents at an integrated, ethnically balanced high school. The independence of the dimensions of ethnic identity were indicated by modest and nonsignificant correlations among the components of ethnic identity, as well as a three-factor solution among the measures of ethnic identity. The correlations among the components of ethnic identity and the factor structure were similar among students in the upper grades (l1th and 12th) and in the lower grades (9th and IOth). Ethnic pride increased with grade level and was lowestfor Anglo and Asian students. Girls were more similar to the norns of their ethnic gPoup than were boys. The importance of multifactorand contextuallyassessed indices ofe fhnic identity is discussed.
The Validity of Measures of Socioeconomic Status of Adolescents
Authors: Ensminger Margaret E. , Forrest Christopher B. , Riley Anne W. , Kang Myungsa , Green Bert F. , Starfield Barbara , Ryan Sheryl A.
Published: March 2007

This study examines the validity of measures of socioeconomic status (SES) as reported by adolescents. Adolescents completed a self-administered questionnaire that included eight measures of SES. Mothers also reported on selected measures of SES. Supporting criterion validity, adolescents and mothers had relatively high agreement on the SES measures. Older adolescents, those less involved in risk behaviors, and those who do better in school gave more accurate SES reports and/or were less likely to have missing SES data. Those in households without fathers were less likely to know fathers’ information. Income was not asked of the adolescents. However, most adolescent-reported SES questions varied systematically and in the expected direction with mothers’income report. In terms of construct validity, the SES measures related to adolescent health measures in the predicted way—that is, those with higher SES were more likely to report better physical and emotional health.
Infant Attachment Security as a Discriminant Predictor of Career Development in Late Adolescence
Authors: Roisman Glenn I. , Bahadur Mudita A. , Oster Harriet
Published: March 2007

This longitudinal study examined the predictive value of infant attachment security at 1 year for career development attitudes and educational aspirations at 18 years. Participants were drawn from an archived longitudinal study and assessed with Waters’ Attachment Q-set through secondary analysis of infancy records. Career development attitudes at 18 years were rated from participant interviews. In addition, parental derogation and idealization at 18 years were assessed to examine the importance of concurrent parent-child relationship factors for career development. Regression analyses revealed that infant attachment explained variance in career development attitudes at 18 years, with secure orientations related to better career development outcomes. Parental idealization and derogation at 18 each explained unique variance in career development indices. As expected, correlational analyses revealed that infant attachment security was unrelated to participants’ educational aspirations at 18 years.
Student Council, Volunteering, Basketball, or Marching Band
Authors: Eccles Jacquelynne S. , Barber Bonnie L.
Published: March 2007

We examined the potential benefits and risks associated with participation in five types of activities: prosocial (church and volunteer activities), team sports, school involvement, performing arts, and academic clubs. Our sample included 1,259 mostly European American adolescents (approximately equal numbers of males and females). First, we explore the link between involvement in these activities and our indicators of positive and negative development. Involvement in prosocial activities was linked to positive educational trajectories and low rates of involvement in risky behaviors. In contrast, participation in team sports was linked to positive educational trajectories and to high rates of involvement in one risky behavior, drinking alcohol. Then, we explore two possible mediators of these associations: peer associations and activity-based identity formation. The evidence supported our hypothesis that group differences in peer associations and activity-based identities help explain activity group differences.
Insect Photoperiodism: Diversity of Results in Night-Break Experiments, Including Nonresponsiveness to Light
Authors: Skopik Steven D. , Takeda Makio , Cain William J. , Patel N.G.
Published: March 2007

Three night-break experiment protocols were utilized in an attempt to help clarify the role of the circadian system in photoperiodic time measurement in the European corn borer, Ostrinia nubilalis. Larvae raised in a light-dark (LD) cycle consisting of 12 hr of light alternating with 12 hr of darkness (LD 12:12), at a constant temperature of 30°C, enter a state of arrested growth and development known as diapause (Takeda and Skopik, 1985). In the present research (Experiment 1), the induction of diapause was prevented by 1-hr light pulses that systematically scanned the dark phase of LD 12:12. Thus, the importance of 12 hr of uninterrupted darkness for maximal induction of diapause is stressed. The same experimental protocol applied to larvae already in diapause (Experiment 2), however, resulted in a bimodal curve of diapause termination. Although this result is consistent with the proposition that a nonperiodic hourglass timer underlies this event (Skopik and Takeda, 1986), it does not rule out the circadian system.

Like LD 12:12, a thermoperiod in constant darkness (12 hr at 4°C alternating with 12 hr at 25°C) also induces diapause. Scanning such a thermoperiod with 1-hr light pulses, however, resulted in only a small effect (reduction of diapause) when light fell in the early to middle part of the warm phase (Experiment 3). Thus, the time-measuring system, under these exper imental conditions, showed only a weak response to light. This unexpected result is discussed with respect to Experiment 1 and two general models that have been proposed to account for photoperiodic time measurement in insects.
The Influence of Prior Wakefulness on REM Sleep
Authors: Knowles John B. , MacLean Alistair W. , Vetere Charles , Young Patricia , Salem Laura , Surridge-David Michela , Coulter Margot
Published: March 2007

Data from studies of naps and of shifted sleep were used to determine the relationship between two measures of rapid eye movement (REM) sleep (percentage of REM in the first 2 hr of sleep and REM latency) and prior wakefulness. For each sample, we calculated the difference between the observed value and that predicted by a cosine function that estimated the circadian rhythm of REM sleep propensity. The difference values were found to correlate reliably with hours and log hours of prior wakefulness. We conclude that while REM sleep is regulated in part by an endogenous circadian oscillator, it is also influenced by the duration of prior wakefulness.
Different Responses of the Circadian System to GABA-Active Drugs in Two Strains of Mice
Authors: Ebihara Shizufumi , Goto Maki , Oshima Itsuki
Published: March 2007

Recent work in our laboratory has shown that sodium pentobarbital injections can induce phase-dependent phase shifts of the circadian rhythm of locomotor activity with the maximum advance at circadian time (CT) 8 and the maximum delay at CT0 in SK/Nga mice but no phase shifts in C57BL/6 mice. In the present study, the possibility that the differences in the effects of pentobarbital on the circadian rhythm may be due to different contributions of the GABA-ergic system to circadian organization in the two strains was tested by compar ing the responses of SK mice with those of C57BL mice to muscimol (2 mg/kg), a GABA receptor agonist, and triazolam (25 mg/kg), which is thought to act by potentiating the action of GABA. The hypothesis that pentobarbital-induced phase shifts of SK mice are mediated by the GABA receptor system was also tested by observing whether the phase-shifting effects of pentobarbital were blocked by bicuculline (0.5 mg/kg), a selective antagonist of GABA, in jected 3 min prior to pentobarbital (30 mg/kg). The results indicated that muscimol induced phase advances at CT8 and phase delays at CT0, and triazolam induced phase advances at CT8 in SK mice. No phase shifts were induced by any treatment in C57BL mice. These results suggest that the role of GABA-ergic systems in circadian organization may be different in SK and C57BL mice. In addition, bicuculline could block the phase-shifting effects of pentobar bital in SK mice, suggesting that the GABA receptor system may mediate phase-shifting effects of pentobarbital in SK mice.
The Mammalian Circadian System: Models and Physiology
Authors: Rusak Benjamin
Published: March 2007

Mammalian circadian rhythms have been studied in great detail using primarily two different methods. One method is usually referred to as the formal analysis of rhythms. Its goal is to describe the properties of both rhythms and their underlying mechanisms, and it aims at the development of adequate mathematical models of the circadian system. The other method is the physiological analysis of the mechanisms that generate and entrain rhythms. Its goal is the identification of the anatomical components of the circadian system and the elu cidation at a cellular and molecular level of how these components work.

This paper reviews how the formal analysis of circadian systems, primarily in rodents, set the agenda for physiological studies, and the degree to which this agenda has been fulfilled. It then discusses how physiological analyses of the system have helped to redefine issues such as the nature and identity of the pacemaker, the nature of the entrainment process, the roles of photic and nonphotic cues, and the role of feedback in the circadian system. The continued commerce between these two approaches has led to a sophisticated appreciation of the com plexities and subtleties of circadian organization in mammals. The further integration of for mal and physiological analyses remains a challenging goal for the future.
Photoperiod and Thermoregulation in Vertebrates: Body Temperature Rhythms and Thermogenic Acclimation
Authors: Heldmaier Gerhard , Steinlechner Stephan , Ruf Thomas , Wiesinger Herbert , Klingenspor Martin
Published: March 2007

Evidence has recently begun to accumulate that photoperiodic responses of mam mals and birds may affect the control of energy balance and thermoregulation. Exposure to short photoperiod can lower the set point for body temperature regulation in birds and mam mals, as well as the voluntarily selected body temperature in ectothermic lizards. This de crease is accompanied by a reorganization of circadian or ultradian rhythms of body temper ature, particularly an increase in periods spent at rest with minimum body temperatures. Short photoperiod is also used as an environmental cue for induction of seasonal torpor or facilita tion of hibernation. During winter, cold tolerance of small mammals is improved by an in crease of nonshivering thermogenesis in brown fat. Thermogenic capacity of brown fat (res piratory enzymes, mitochondria, uncoupling protein) is enhanced in response to short pho toperiod. This response is mediated via an increase in the activity of sympathetic innervation in brown fat. Moreover, an exposure to short photoperiod prior to low temperatures may act in preparing brown fat for facilitated thermogenesis during acclimation to cold. This shows that photoperiodic control not only affects energy balance indirectly via the control of repro duction or body mass, but may directly interact with central control of thermoregulation and may influence the process of acclimatization.
The Influence of Time of Day on the Foraging Behavior of the Honeybee, Apis mellifera
Authors: Moore Darrell , Siegfried Dana , Wilson Richard , Rankin Mary Ann
Published: March 2007

The honeybee time sense, or Zeitgedächtnis, is highly adaptive, allowing bees to synchronize their foraging behavior with the peak time of daily floral nectar rhythms. Each foraging group within the honeybee colony shows a high degree of fidelity to one species of flower. Across the day, the temporal accuracy of foraging visits to experimental feeding times varies considerably, being nearly exact for morning-trained foraging groups but becoming less so for foraging groups trained later in the day. The evidence gained in this study suggests that the diel change in accuracy exhibited by foraging groups, which persists after the removal of many potential environmental time cues, is an endogenously driven behavior pattern. Fur thermore, it appears that individual bees are continuously and accurately aware of the time of day, but are programmed to forage with greater anticipation to late-day food sources. Therefore, two separate processes contributing to the honeybee time sense are implicated. The first varies with time of day and determines the amount of anticipatory activity directed toward the food source. The second process is invariant across the day and is involved with the individual forager's continuous, accurate awareness of time.
Localization of the Circadian Pacemakers of Hemideina thoracica (Orthoptera; Stenopelmatidae)
Authors: Waddell Barbara , Lewis Robert D. , Engelmann Wolfgang
Published: March 2007

The location of the circadian pacemakers of the orthopteran Hemideina thoracica (White) has been investigated through observation of the effects of surgical removal of brain tissues (principally optic lobes and tracts) on free-running and entrained locomotor rhythms. Bilobectomy and severance of optic tracts invariably resulted in arrhythmicity, whereas rhythmicity was sustained following unilateral lobectomy, generally with increases in the free-running period (FRP) and decreases in both the active-phase lengths and activity-to-rest ratios of the rhythm. Bilobectomized subjects could be entrained by temperature cycles, but exhibited no transients or residual rhythmicity, indicating that temperature brought about a direct response or masking effect. These results support the hypothesis that the circadian locomotor pacemakers of Hemideina are located within each optic lobe, and that there are no extraoptic centers for the control of the timing of locomotor activity. Although confirmation of the pacemaker role of the optic lobes requires transplantation of the tissues, the conclusion may be drawn by inference from other studies (e.g., Leucophaea maderae—Page , 1983; Gryllus bimacu latus—Tomioka and Chiba, 1986). Light entrainment continued after surgical blinding and blackening of the compound eyes and ocelli, supporting the view that direct illumination of neural tissue through the cuticle may be one possible pathway for light entrainment.
Circannual Rhythms of Gonadal Maturation in Female Rainbow Trout (Oncorhynchus mykiss)
Authors: Duston James , Bromage Niall
Published: March 2007

Individually identified, 2-year-old female rainbow trout were maintained for up to 51 months on a constant schedule of 6 hr light and 18 hr darkness (LD 6:18), constant temperature (8.5-9.0°C), and constant feeding rate. The fish exhibited free-running circannual rhythms of gonadal maturation and ovulation, which were self-sustaining for up to three cycles. The periodicity of the rhythm showed variation between fish and in successive cycles for the same fish, ranging from approximately 11 to 15 months.
Suprachiasmatic Nucleus and Photic Entrainment of Circannual Rhythms in Ground Squirrels
Authors: Lee Theresa M. , Zucker Irving
Published: March 2007

The efficacy of photoperiod as a zeitgeber for entrainment of circannual body weight and estrous rhythms was tested in female golden-mantled ground squirrels maintained for 3 or more years in either a simulated natural photoperiod (SNP) or a fixed LD 14:10 photoperiod (FP). The role of the retinohypothalamic tract—suprachiasmatic nucleus (RHT-SCN) projection in photic entrainment was assessed in animals that sustained destruction of the SCN (SCNx ). Circannual rhythms were lengthened by the SNP as compared to the FP. Mean periods (τ's) for neurologically intact animals in the third year of testing were 49.6 ± 0.3 weeks and 43.1 ± 1.2 weeks ( p < 0.001) for the SNP and FP groups, respectively; furthermore, 56% and 7% of animals in these groups had τ's not significantly different from 365 days ( p < 0.005), and within-group variability was lower for SNP than for FP squirrels ( p < 0.01). SCNx squirrels differed from animals with the SCN intact (SCNc), as evidenced by higher within-group variability ( p < 0.001); only 29% of SCNx squirrels had τ's not different from 365 days ( p < 0.03 compared to the SCNc group). The coupling between estrous and body weight rhythms that was evident in SCN-intact SNP and FP squirrels was disrupted in SCNx animals. The RHT-SCN pathway is implicated in entrainment and in maintenance of normal phase relations among the several circannual rhythms. In a second experiment, female squirrels were maintained for 2.5 years in an accelerated SNP that compressed two normal annual photocycles into each calendar year. Of 12 squirrels, 3 had τ's that did not differ significantly from 6 months; 6 had τ's equivalent to 12 months; and 3 had τ's significantly different from both 6 months and 12 months. The data suggest that photoperiod is a major zeitgeber for entrainment of golden-mantled ground squirrels' circannual rhythms.
Phase Resetting of the Neurospora crassa Circadian Oscillator: Effects of Inositol Depletion on Sensitivity to Light
Authors: Lakin-Thomas Patricia L.
Published: March 2007

The input pathway between the blue-light photoreceptor and the circadian oscillator of Neurospora crassa has not yet been identified. To test the hypothesis that an inositol phospholipid signaling system might be involved in blue-light signal transduction, phase resetting by light was assayed in the inositol-requiring inl strain under conditions of inositol depletion. Phase-resetting curves and dose-response curves indicated that cultures maintained on low inositol (25 μM) were several orders of magnitude more sensitive to light than those maintained on high inositol (250 μM). This difference in light sensitivity was a property of inositol auxotrophy and was not seen in the wild type or in an inositol-independent inl + revertant. Phase resetting by temperature was not affected by inositol depletion, indicating that the effect on light resetting is specific to the light input pathway and is not the result of a change in the amplitude of the oscillator itself. The results indicate an indirect role for inositol metabolites in the light input pathway—one that is not likely to involve direct participation of an inositol phospholipid signal transduction mechanism.
Photoperiodic Time Measurement and a Graded Response in a Cockroach
Authors: Wassmer Gary T. , Page Terry L.
Published: March 2007

Almost exclusively, photoperiodic insects respond to a given photoperiod in one of two ways: a "long-day" response or a "short-day" response. Intermediate responses occur only at a very restricted range of photoperiods (often less than 30 min) and are generally population phenomena rather than intermediate responses of individuals. In contrast, individuals of the wood roach, Parcoblatta pennsylvanica, show intermediate responses over a broad range of photoperiods.

We examined the effect of constant light, constant darkness, and photoperiods ranging from 10 to 18 hr of light per 24 hr on growth rate as measured by weight gain, and found a robust photoperiodic response. Nymphs raised in photoperiods with light periods (photophases) from 0 to 12 hr gained little weight, whereas those in LD 18:6 were almost 15 times heavier. This is the first report of a photoperiodic response curve for a cockroach. Interestingly, there was a linear relationship between the duration of the photophase and weight gain over a broad range of photoperiods (LD 12:12 to LD 18:6; r2 = 0.99). Statistical analysis showed that the intermediate responses were attributable to individuals' growing at an intermediate rate. Another interesting observation was that all larval stages appeared to be capable of perceiving and responding to photoperiodic signals. The results of further experiments using non-24-hr photoperiods were consistent with the existence of a circadian component in the photoperiodic time measurement in this species.
Deriving a "Phase Response Curve" from Adjustment to Simulated Time Zone Transitions
Authors: Minors D.S. , Waterhouse J.M.
Published: March 2007

Thirty-eight subjects in groups of two to four have been subjected to simulated time zone transitions of 8 hr eastward, 8 hr westward, or 12 hr; all experiments have taken place in a temporal isolation unit, in which the light intensity during the waking periods was 250-300 lux. Circadian rhythms of rectal temperature have been used as a marker of the process of adjustment, the data being analyzed before (raw) and after "purification." Conventional results have been obtained, but when the data have been treated appropriately, they have produced a relationship between shift of the sleep-activity cycle and shift of the temperature rhythms that shows many characteristics of a phase response curve. Even though the factor or factors causing such adjustment are unknown, the results confirm that changes of a consonant set of "weak" zeitgebers is sufficient for entrainment to a new time zone to occur.
The Circadian Rhythm of Thermoregulation in Japanese Quail: III. Effects of Melatonin Administration
Authors: Underwood Herbert , Edmonds Kent
Published: March 2007

Recent studies indicate that the circadian pacemakers in the eyes of Japanese quail are coupled to the rest of the circadian system by both neural and hormonal outputs. The effects of exogenous melatonin administration on cir cadian body temperature and activity rhythms of quail were tested to determine whether melatonin could be the hormonal link involved. Continuous melatonin administration caused arrhythmicity or period changes in the body temperature and activity rhythms of pinealectomized and sham-pinealectomized birds held in constant darkness and also significantly decreased the amplitude of the body temperature rhythms of normal birds held on light:dark 12:12. Further, mela tonin entrained the body temperature and activity rhythms of normal birds when administered daily via the drinking water. The results show that melatonin can affect the circadian system of quail and support the hypothesis that melatonin is importantly involved in linking pacemakers in the eyes to the rest of the circadian system.