bluuebunny/crossref_metadata_2025 huggingface dataset:
“Being Called Awake”: The Role Of Transformative Learning In The Lives Of Environmental Activists
Authors: Kovan Jessica T. , Dirkx John M.
Published: April 2003

Environmental and other nonprofit activists often confront what Parker Palmer referred to as a loss of heart, particularly where working conditions challenge the capacity of practitioners to sustain their commitment. The purpose of this qualitative study was to better understand the process of learning and self-renewal in the lives of experienced and committed environmental activists. Findings suggest that their lives are characterized by struggles that represent a profound form of learning, involving recognition and understanding of one’s work as a calling or vocation as well as exemplifying the kind of transformative learning reflected in Jung’s concept of individuation.
Support and Strain in Pregnant and Parenting Adolescents’ Sibling Relationships
Authors: Gee Christina B. , Nicholson Melba J. , Osborne Lori N. , Rhodes Jean E.
Published: April 2003

Social support and social strain in adolescent mothers’ sibling relationships were investigated. Participants were 536 (93% African American), primarily low-income, adolescents attending an alternative school for pregnant and parenting teens. More than half of the participants nominated at least one sibling as a source of support. Older sisters were nominated twice as often as any other sibling group. In addition, older sisters provided both the greatest variety and amount of support in comparison to the other sibling groups. Support from older sisters was not associated with adolescent mothers’ psychological adjustment. However, strain in relationships with older brothers and older sisters was associated with increased psychological distress.
Role Models and Psychosocial Outcomes Among African American Adolescents
Authors: Bryant Alison L. , Zimmerman Marc A.
Published: April 2003

The authors examined who 679 African American ninth-graders from urban environments look up to and how their role model choices relate to substance use, delinquency, academic engagement, and psychological well-being. Male adolescents without male role models and females identifying brothers as role models reported the most problem behavior. Adolescents with paternal male role models had the most positive school outcomes, no differences were found in psychological well-being among adolescents in terms of their male role models. The presence of female role models, in contrast, was associated with psychological well-being such that adolescents with maternal role models reported the least distress. Adolescents without female role models had the lowest grades and most negative school attitudes. These findings remained when parental support, family conflict, and father presence in the household were controlled, suggesting role model effects are separate from parenting effects. Our findings support and expand on the notion that having someone to look up to is critical for African American youths’ development.
Nonbehavioral Correlates of Juvenile Delinquency: Communications of Detained and Nondetained Young People About Social Limits
Authors: Grietens Hans , Rink Jacobus , Hellinckx Walter
Published: April 2003

Focusing on nonbehavioral correlates of juvenile delinquency, young people’s attitudinal reactions toward social limits were measured by means of the Standard Reaction Instrument (SRI). Responses of 85 detained young offenders were compared with those of 390 nondetained controls. Relationships between attitudinal reactions and scores on the Youth Self-Report’s delinquent behavior and aggressive behavior syndromes were examined. Significant differences between detained and nondetained young people were found with regard to knowledge of behavioral alternatives and behavioral intentions. Furthermore, in nondetained young people, significant relationships were found between transgressive intentions, self-oriented motivations, here-and-now oriented motivations, and scores on delinquent behavior and aggressive behavior. Young people reporting high rates of undersocialized behavior were more inclined to transgress social limits and more often attributed their intentions to self-oriented motivations and less often to here-and-now-oriented motivations. The results supported the self-presentation theory on juvenile delinquency.
Risk Behaviors Among Young Mexican American Gang-Associated Females: Sexual Relations, Partying, Substance Use, and Crime
Authors: Cepeda Alice , Valdez Avelardo
Published: April 2003

This research focuses on young Mexican American girls who are not formal gang members yet participate in street-based activities of male gangs and engage in risk behaviors. These females comprise a larger proportion associated with male gangs in inner-city neighborhoods than actual female gang members. Using a qualitative design, the article presents a typology of Mexican American females that reveals a hierarchy based on exposure to four risk-related activities: sexual relations, partying, substance use, and crime. Findings illustrate how outcomes associated with these activities vary according to the girl’s relationship to the male gang and status within the community. Also, regardless of their relationship to the gang, participation in these activities resulted in different degrees of negative outcomes. The study concludes that problems associated with these females must go beyond being viewed as individual problems but rather seen within the social, cultural, and economic conditions of their environment.
Modeling Mexican Americans’ Educational Expectations: Longitudinal Effects of Variables Across Adolescence
Authors: Trusty Jerry , Plata Maximino , Salazar Carmen F.
Published: April 2003

Using a national sample of Mexican Americans, the authors developed structural equation models of the effects of four eighth-grade latent variables on educational expectations assessed 6 years later. Models for Mexican American women and men did not differ from one another. The latent variable, parents’ influences, had a strong positive effect on educational expectations at late adolescence. Parents’ influences dominated the effects of the other latent independent variables, socioeconomic status, eighth-grade achievement test scores, and self-perceptions. The four eighth-grade latent variables explained 41% of the variability in educational expectations at late adolescence. The findings reveal consistencies and inconsistencies with previous research findings and models.
Cross-Generational Parenting Influences on Psychosocial Functioning of Adolescent Mothers in Substitute Care
Authors: Felix Erika D. , Kelly Abesie O. , Poindexter LaShaunda M. , Budd Karen S.
Published: April 2003

This study examined the cross-generational influence of adolescent parenthood on psychosocial functioning with a random sample of adolescent mothers in state substitute care due to child abuse or neglect in their family of origin. Participants reported if their main parenting figure was an adolescent parent or not, their educational attainment, and their level of parenting stress. Participants whose main parenting figure was an adolescent parent reported significantly higher parenting stress and lower educational attainment than participants whose main parenting figure was not an adolescent parent. The two groups of adolescent mothers did not differ in their childbearing history or past substitute care experience. These findings highlight the need for research and interventions to address cross-generational influences on educational and parenting difficulties among teenage mothers in substitute care.
Religious Socialization: A Test of the Channeling Hypothesis of Parental Influence on Adolescent Faith Maturity
Authors: Martin Todd F. , White James M. , Perlman Daniel
Published: April 2003

Recent research on intergenerational faith transfer has argued that (a) parents have a direct effect on the adolescence acquisition of religiosity and (b) parental effects are mediated through congregation and peers. This study tests the channeling hypothesis, which argues that parental influences are mediated through both peer selection and congregation selection. It examines both direct and indirect effects that parental influence has on the religiosity of offspring. A national survey of 11,000 adolescents and adults in six Protestant denominations produced a subsample of 2,379 youth. Contrary to the channeling hypothesis, the research showed that peer influence and parental influence remained stable during the adolescent years. Parental influence did not dramatically increase or decrease with age. Some findings support the channeling hypothesis, particularly the mediating effect of parents through peer influences. The findings of this study are discussed in light of the contradictory findings from other studies.
Mapping Quantitative Trait Loci Affecting Circadian Photosensitivity in Retinally Degenerate Mice
Authors: Yoshimura Takashi , Yokota Yuki , Ishikawa Akira , Yasuo Shinobu , Hayashi Noriko , Suzuki Tohru , Okabayashi Naritoshi , Namikawa Takao , Ebihara Shizufumi
Published: April 2003

It is known that retinally degenerate C57BL/6J ( rd/rd) mice have unattenuated circadian photosensitivity. However, the authors have previously found that CBA/J ( rd/rd) mice that carry the same rd mutation have attenuated circadian photosensitivity compared to normal CBA/N (+/+) mice. In the present study, a quantitative trait locus (QTL) analysis using C57BL/6J ( rd/rd) and CBA/J ( rd/rd) mice was conducted in order to identify the genes affecting circadian photosensitivity of the rd mice. As a result, several putative QTLs on three separate chromosomes (8, 12, 17) were detected, which indicates that circadian photosensitivity in rd mice is altered by multiple genes. Identification of these genes may provide new insights into the understanding of regulation of circadian photoentrainment and sleep-wake disorders.
Photic Resetting of the Human Circadian Pacemaker in the Absence of Conscious Vision
Authors: Klerman E. B. , Shanahan T. L. , Brotman D. J. , Rimmer D. W. , Emens J. S. , Rizzo J. F. , Czeisler C. A.
Published: April 2003

Ocular light exposure patterns are the primary stimuli for entraining the human circadian system to the local 24-h day. Many totally blind persons cannot use these stimuli and, therefore, have circadian rhythms that are not entrained. However, a few otherwise totally blind persons retain the ability to suppress plasma melatonin concentrations after ocular light exposure, probably using a neural pathway that includes the site of the human circadian pacemaker, suggesting that light information is reaching this site. To test definitively whether ocular light exposure could affect the circadian pacemaker of some blind persons and whether melatonin suppression in response to bright light correlates with light-induced phase shifts of the circadian system, the authors performed experiments with 5 totally blind volunteers using a protocol known to induce phase shifts of the circadian pacemaker in sighted individuals. In the 2 blind individuals who maintained light-induced melatonin suppression, the circadian system was shifted by appropriately timed bright-light stimuli. These data demonstrate that light can affect the circadian pacemaker of some totally blind individuals— either by altering the phase of the circadian pacemaker or by affecting its amplitude. They are consistent with data from animal studies demonstrating that there are different neural pathways and retinal cells that relay photic information to the brain: one for conscious light perception and the other for non-image-forming functions.
Circadian Adaptation to Night-Shift Work by Judicious Light and Darkness Exposure
Authors: Boivin Diane B. , James Francine O.
Published: April 2003

In this combined field and laboratory investigation, the authors tested the efficacy of an intervention designed to promote circadian adaptation to night-shift work. Fifteen nurses working permanent night schedules ([.greaterequal] 8 shifts/ 15 days) were recruited from area hospitals. Following a vacation period of [.greaterequal] 10 days on a regular daytime schedule, workers were admitted to the laboratory for the assessment of circadian phase via a 36-h constant routine. They returned to work ~ 12 night shifts on their regular schedules under one of two conditions. Treatment group workers ( n = 10, mean age ± SD = 41.7 ± 8.8 years) received an intervention including 6 h of intermittent bright-light exposure in the workplace (~ 3243 lux) and shielding from bright morning outdoor light with tinted goggles (15% visual light transmission). Control group workers ( n = 9, mean age ± SD = 42.0 ± 7.2 years) were observed in their habitual work environments. On work days, participants maintained regular sleep/wake schedules including a single 8-h sleep/darkness episode beginning 2 h after the end of the night shift. A second 36-h constant routine was performed following the series of night shifts. In the presence of the intervention, circadian rhythms of core body temperature and salivary melatonin cycles were delayed by an average (± SEM) of –9.32 ± 1.06 h and –11.31 ± 1.13 h, respectively. These were significantly greater than the phase delays of –4.09 ± 1.94 h and –5.08 ± 2.32 h displayed by the control group ( p = 0.03 and p = 0.02, respectively). The phase angle between circadian markers and the shifted schedule was reestablished to its baseline position only in the treatment group of workers. These results support the efficacy of a practical intervention for promoting circadian adaptation to night-shift work under field conditions. They also underline the importance of controlling the overall pattern of exposure to light and darkness in circadian adaptation to shifted sleep/wake schedules.
Saturation of Enzyme Kinetics in Circadian Clock Models
Authors: Kurosawa Gen , Iwasa Yoh
Published: April 2003

From the mathematical study of simple models for circadian rhythm, the authors identified a clear effect of saturation in the enzyme kinetics on the promotion or suppression of a sustained oscillation. In the models, a clock gene ( pergene) is transcribed to produce mRNAs, which are translated to produce proteins in the cytosol, which are then transported to the nucleus and suppress the transcription of the gene. The negative feedback loop with a long time delay creates sustained oscillation. All the enzymatic reactions (e.g., degradation, translation, and modification) are assumed to be of Michaelis-Menten type. The reaction rate increases with the amount of substrate but saturates when it is very large. The authors prove mathematically that the saturation in any of the reactions included in the feedback loop (in-loop reaction steps) suppresses the oscillation, whereas the saturation of both degradation steps and the back transport of the protein to cytosol (branch reaction steps) makes the oscillation more likely to occur. In the experimental measurements of enzyme kinetics and in published circadian clock simulators, in-loop reaction steps have a small saturation index whereas branch reaction steps have a large saturation index.
Defined Cell Groups in the Rat Suprachiasmatic Nucleus Have Different Day/Night Rhythms of Single-Unit Activity In Vivo
Authors: Saeb-Parsy K. , Dyball R. E. J.
Published: April 2003

The electrical activity of the rat suprachiasmatic nucleus (SCN) was examined in anesthetized rats in vivo using single-unit electrophysiological techniques. The present data confirm the daily variation in the electrical activity of the SCN previously reported in vitro and in vivo using multiple-unit recording techniques. They further suggest that subpopulations of suprachiasmatic neurons with different neural connections have a different daily rhythm of activity. Neurons in the SCN region showed a significant rhythm of activity ( p = 0.034; Kruskall-Wallis analysis of variance [KW-ANOVA]). The greatest activity occurred during the second part of the light period (ZT 10-12), and the lowest activity occurred in the early part of the light period (ZT 0-2). The subgroup of cells in the suprachiasmatic region with output projections to the arcuate nucleus (ARC) and/or supraoptic nucleus (SON) regions also showed a significant rhythm ( p = 0.001; K-W ANOVA). Their activity appeared to show two peaks near the light-dark (ZT 10-12) and dark-light (ZT 22-24) transition periods with the lowest activity at ZT 16-18. This rhythm was significantly different ( p = 0.016) from that of neurons without an output projection to the ARC and/or SON. Retinorecipient suprachiasmatic neurons appeared to have a less robust daily rhythm in their activity. The change in the firing behavior of the cells was not reflected simply by changes in mean firing rate. Examination of the coefficient of variation of the interspike interval distribution of cells at different times of day revealed changes in the firing pattern of cells in the SCN region that did not have output projections ( p = 0.032; K-W ANOVA). The present results thus suggest that the SCN is composed of a heterogeneous population of neurons and that different rhythms of activity are expressed by neurons with different neural connections. There were changes in both firing pattern and firing rate.
Testosterone Suppresses Circadian Responsiveness to Social Cues in the Diurnal Rodent Octodon degus
Authors: Jechura Tammy J. , Walsh Jacquelynn M. , Lee Theresa M.
Published: April 2003

The diurnal, social rodent Octodon degus displays a robust sex difference in the ability to use social cues to facilitate reentrainment following a phase advance of the light cycle. Adult females housed with a female social cue donor reentrained 25% to 40% faster than did females reentraining alone. However, reentrainment rates of males were unaffected by exposure to female social cues during reentrainment. The authors hypothesized that males were less sensitive to the reentrainment-enhancing effects of social cues and that their higher threshold to the stimuli could be overcome if the social cues were either increased in strength or salience. Housing a male with two females significantly shortened the time to reentrain following a 9-h phase advance ( p = 0.002). Housing with a sister had no effect on reentrainment. Therefore, male degus are able to respond to social cues but require the stimulus to be stronger than that for females. The effect of testosterone was tested by comparing reentrainment rates of castrated males before and after testosterone replacement both with and without a female social cue donor. Castrated males responded to a single female social cue donor, reentraining 35% faster than when housed alone ( p = 0.006), whereas the time to reentrainment of intact males and males with testosterone capsule implants did not differ. Intact females were also implanted with testosterone and phase shifted with and without donors. Testosterone treatment eliminated the increase in reentrainment rates in the presence of social cues. The authors conclude that the rate of recovery from odor-enhanced phase shifts is modulated by activational effects of testosterone in male degus. Testosterone is also effective in suppressing social cue responsiveness in females, suggesting that testosterone’s effects on responsiveness are not sexually dimorphic. This hormonal effect likely occurs by altering sensory system functions or CNS response to sensory information.
Photoperiodic Adjustments in Immune Function Protect Siberian Hamsters from Lethal Endotoxemia
Authors: Prendergast Brian J. , Hotchkiss Andrew K. , Bilbo Staci D. , Kinsey Steven G. , Nelson Randy J.
Published: April 2003

Seasonal changes in day length enhance or suppress components of immune function in individuals of several mammalian species. Siberian hamsters ( Phodopus sungorus) exhibit multiple changes in neuroendocrine, reproductive, and immune function after exposure to short days. The manner in which these changes are integrated into the host response to pathogens is not well understood. The present experiments tested the hypothesis that short-day changes in immune function alter the pathogenesis of septic shock and survival after challenge with endotoxin. Male and female Siberian hamsters raised in long-day photoperiods were transferred as adults to short days or remained in their natal photoperiod. Six to 8 weeks later, hamsters were injected i.p. with 0, 1, 2.5, 10, 25, or 50 mg/kg bacterial lipopolysaccharide (LPS) (the biologically active constituent of endotoxin), and survival was monitored for 96 h. Short days significantly improved survival of male hamsters treated with 10 or 25 mg/kg LPS and improved survival in females treated with 50 mg/kg LPS. Transfer from long to short days shifted the LD50 in males by approximately 90%, from 5.3 to 9.9 mg/kg, and in females from 11.1 to 15.0 mg/kg ([#002B]35%). Long-day females were more resistant than were males to lethal endotoxemia. In vitro production of the proinflammatory cytokine TNFα in response to LPS stimulation was significantly lower in macrophages extracted from short-day relative to long-day hamsters, as were circulating concentrations of TNFα in vivo after i.p. administration of LPS, suggesting that diminished cytokine responses to LPS in short days may mitigate the lethality of endotoxemia. Adaptation to short days induces changes in immune parameters that affect survival in the face of immune challenges.
Inferior Retinal Light Exposure Is More Effective than Superior Retinal Exposure in Suppressing Melatonin in Humans
Authors: Glickman Gena , Hanifin John P. , Rollag Mark D. , Wang Jenny , Cooper Howard , Brainard George C.
Published: April 2003

Illumination of different areas of the human retina elicits differences in acute light-induced suppression of melatonin. The aim of this study was to compare changes in plasma melatonin levels when light exposures of equal illuminance and equal photon dose were administered to superior, inferior, and full retinal fields. Nine healthy subjects participated in the study. Plexiglass eye shields were modified to permit selective exposure of the superior and inferior halves of the retinas of each subject. The Humphrey Visual Field Analyzer was used both to confirm intact full visual fields and to quantify exposure of upper and lower visual fields. On study nights, eyes were dilated, and subjects were exposed to patternless white light for 90 min between 0200 and 0330 under five conditions: (1) full retinal exposure at 200 lux, (2) full retinal exposure at 100 lux, (3) inferior retinal exposure at 200 lux, (4) superior retinal exposure at 200 lux, and (5) a dark-exposed control. Plasma melatonin levels were determined by radioimmunoassay. ANOVA demonstrated a significant effect of exposure condition ( F = 5.91, p < 0.005). Post hoc Fisher PLSD tests showed significant ( p [#003C] 0.05) melatonin suppression of both full retinal exposures as well as the inferior retinal exposure; however, superior retinal exposure was significantly less effective in suppressing melatonin. Furthermore, suppression with superior retinal exposure was not significantly different from that of the dark control condition. The results indicate that the inferior retina contributes more to the light-induced suppression of melatonin than the superior retina at the photon dosages tested in this study. Findings suggest a greater sensitivity or denser distribution of photoreceptors in the inferior retina are involved in light detection for the retinohypothalamic tract of humans.
Life between Clocks: Daily Temporal Patterns of Human Chronotypes
Authors: Roenneberg Till , Wirz-Justice Anna , Merrow Martha
Published: April 2003

Human behavior shows large interindividual variation in temporal organization. Extreme “larks” wake up when extreme “owls” fall asleep. These chronotypes are attributed to differences in the circadian clock, and in animals, the genetic basis of similar phenotypic differences is well established. To better understand the genetic basis of temporal organization in humans, the authors developed a questionnaire to document individual sleep times, self-reported light exposure, and self-assessed chronotype, considering work and free days separately. This report summarizes the results of 500 questionnaires completed in a pilot study. Individual sleep times show large differences between work and free days, except for extreme early types. During the workweek, late chronotypes accumulate considerable sleep debt, for which they compensate on free days by lengthening their sleep by several hours. For all chronotypes, the amount of time spent outdoors in broad daylight significantly affects the timing of sleep: Increased self-reported light exposure advances sleep. The timing of self-selected sleep is multifactorial, including genetic disposition, sleep debt accumulated on workdays, and light exposure. Thus, accurate assessment of genetic chronotypes has to incorporate all of these parameters. The dependence of human chronotype on light, that is, on the amplitude of the light:dark signal, follows the known characteristics of circadian systems in all other experimental organisms. Our results predict that the timing of sleep has changed during industrialization and that a majority of humans are sleep deprived during the workweek. The implications are far ranging concerning learning, memory, vigilance, performance, and quality of life.
Distribution of PER Protein, Pigment-Dispersing Hormone, Prothoracicotropic Hormone, and Eclosion Hormone in the Cephalic Nervous System of Insects
Authors: Závodská Radka , Šauman Ivo , Sehnal František
Published: April 2003

Investigations performed on adult insects revealed that putative components of the central pacemaker, the protein Period (PER) and the pigment-dispersing hormone (PDH), are immunocytochemically detectable in discrete sets of brain neurons throughout the class of Insecta, represented by a bristletail, mayfly, damselfly, 2 locust species, stonefly, 2 bug species, goldsmith beetle, caddisfly, honeybee, and 2 blowfly species. The PER-positive cells are localized in the frontal protocerebrum and in most species also in the optic lobes, which are their only location in damselfly and goldsmith beetle. Additional PER-positive cells occur in a few species either in the deuto- and tritocerebrum or in the suboesophageal ganglion. The PER staining was always confined to the cytoplasm. The PDH immunoreactivity consistently occurs in a cluster of perikarya located frontoventrally at the proximal edge of the medulla. The mayfly and both locust species possess additional PDH neurons in 2 posterior cell clusters at the proximal edge of the medulla, and mayfly, waterstrider, and 1 of the blowfly species in the central brain. PDH-positive fibers form a fanlike arrangement over the frontal side of the medulla. Two or just 1 bundle of PDH-positive fibers run from the optic lobe to the protocerebrum, with collaterals passing over to the contralateral optic lobe. Antisera to the prothoracicotropic (PTTH) and the eclosion (EH) hormones, which in some insects regulate the molting and ecdysis rhythms, respectively, typically react with a few neurons in the frontal protocerebrum. However, the PTTH-positive neurons of the mayfly and the damselfly and the EH-positive neurons of the caddisfly are located in the suboesophageal ganglion. No PTTH-like antigen was detected in locusts, and no EH-like antigens were detected in the damselfly, stonefly, locusts, and the honeybee. There are no signs of co-localization of the PER-, PDH-, PTTH-, and EH-like antigens in identical neurons.
Is Sleep per se a Zeitgeber in Humans?
Authors: Danilenko Konstantin V. , Cajochen Christian , Wirz-Justice Anna
Published: April 2003

It is not clear whether shifting of sleep per se, without a concomitant change in the light-dark cycle, can induce a phase shift of the human circadian pacemaker. Two 9-day protocols (crossover, counterbalanced order) were completed by 4 men and 6 women (20-34 years) after adherence to a 2330 to 0800 h sleep episode at home for 2 weeks. Following a modified baseline constant routine (CR) protocol on day 2, they remained under continuous near-darkness (< 0.2 lux, including sleep) for 6 days. Four isocaloric meals were equally distributed during scheduled wakefulness, and their timing was held constant. Subjects remained supine in bed from 2100 to 0800 h on all days; sleep was fixed from 2330 to 0800 h in the control condition and was gradually advanced 20 min per day during the sleep advance condition until a 2-h difference had been attained. On day 9, a 25 to 27 h CR protocol (~0.1 lux) was carried out. Phase markers were the evening decline time of the core body temperature (CBT) rhythm and salivary melatonin onset (3 pg/ml threshhold). In the fixed sleep condition, the phase drift over 7 days ranged from +1.62 to –2.56 h (for both CBT and melatonin rhythms, which drifted in parallel). The drifts were consistently advanced in the sleep advance schedule by +0.66 ± 0.23 (SEM) h for CBT ( p = 0.02) and by 0.27 ± 0.14 h for melatonin rhythms ( p = 0.09). However, this advance was small to medium according to effect size. Sleep per se may feed back onto the circadian pacemaker, but it appears to be a weak zeitgeber in humans.
Clock Gene Daily Profiles and Their Phase Relationship in the Rat Suprachiasmatic Nucleus Are Affected by Photoperiod
Authors: Sumová Alena , Jáč Martin , Sládek Martin , Šauman Ivo , Illnerová Helena
Published: April 2003

Rhythmicity of the rat suprachiasmatic nucleus (SCN), a site of the circadian pacemaker, is affected by daylength; that is, by the photoperiod. Whereas various markers of rhythmicity have been followed, so far there have been no studies on the effect of the photoperiod on the expression of the clock genes in the rat SCN. To fill the gap and to better understand the photoperiodic modulation of the SCN state, rats were maintained either under a long photoperiod with 16 h of light and 8 h of darkness per day (LD16:8) or under a short LD8:16 photoperiod, and daily profiles of Per1, Cry1, Bmal1 and Clock mRNA in darkness were assessed by in situ hybridization method. The photoperiod affected phase, waveform, and amplitude of the rhythmic gene expression as well as phase relationship between their profiles. Under the long period, the interval of elevated Per1 mRNA lasted for a longer and that of elevated Bmal1 mRNA for a shorter time than under the short photoperiod. Under both photoperiods, the morning and the daytime Per1 and Cry1 mRNA rise as well as the morning Bmal1 mRNA decline were closely linked to the morning light onset. Amplitude of Per1, Cry1, and Bmal1 mRNA rhythms was larger under the short than under the long photoperiod. Also, under the short photoperiod, the daily Clock mRNA profile exhibited a significant rhythm. Altogether, the data indicate that the whole complex molecular clockwork in the rat SCN is photoperiod dependent and hence may differ according to the season of the year.
Aging Alters Circadian and Light-Induced Expression of Clock Genes in Golden Hamsters
Authors: Kolker Daniel E. , Fukuyama Hiroo , Huang David S. , Takahashi Joseph S. , Horton Teresa H. , Turek Fred W.
Published: April 2003

Aging alters numerous aspects of circadian biology, including the amplitude of rhythms generated by the suprachiasmatic nuclei (SCN) of the hypothalamus, the site of the central circadian pacemaker in mammals, and the response of the pacemaker to environmental stimuli such as light. Although previous studies have described molecular correlates of these behavioral changes, to date only 1 study in rats has attempted to determine if there are age-related changes in the expression of genes that comprise the circadian clock itself. We used in situ hybridization to examine the effects of age on the circadian pattern of expression of a subset of the genes that comprise the molecular machinery of the circadian clock in golden hamsters. Here we report that age alters the 24-h expression profile of Clock and its binding partner Bmal1 in the hamster SCN. There is no effect of age on the 24-h profile of either Per1 or Per2 when hamsters are housed in constant darkness. We also found that light pulses, which induce smaller phase shifts in old animals than in young, lead to decreased induction of Per1, but not of Per2, in the SCN of old hamsters.
DNA Arrays: Applications and Implications for Circadian Biology
Authors: Sato Trey K. , Panda Satchidananda , Kay Steve A. , Hogenesch John B.
Published: April 2003

DNA arrays can be powerful tools to investigate transcriptional regulation of biological systems in a highly parallel and genome-wide manner. Their use has furthered the investigation of basic cell and developmental biology and is now being applied toward the understanding and diagnosis of human disease. DNA arrays are of particular use in the study of circadian biology because the clock is, at its heart, a transcriptional/translational feedback loop. Here, we review the underlying technology behind DNA arrays, discuss general applications, and focus on the use of the arrays in the study of circadian biology in plants, flies, and mice.
Light-Induced Phase Shifts in Mice Lacking mPER1 or mPER2
Authors: Bae Kiho , Weaver David R.
Published: April 2003

Three homologs of the Drosophila Period gene have been identified in mammals. In mice, these three genes ( mPer1, mPer2, and mPer3) have distinct roles in the circadian clockwork. While products of mPer1 and mPer2 play important roles in the maintenance of circadian rhythmicity, mPer3 gene products are dispensable for rhythmicity. Several studies also implicate mPER1 and mPER2 in transduction of photic information to the core circadian clockwork. The phase-shifting effects of light were examined in mPER1-deficient and mPER2-deficient mice using T cycle paradigms, in which mice received 1 h of light per day at an interval of T hours. To assess phase delays, repeated exposure to 1 h of light per day at T = 24 was used. To assess phase advances, exposure to 1-h light pulses at T = 22-h intervals was used. The degeneration of rhythmicity in the mutant mice prevented assessment of a response in most cases. Nevertheless, clear examples of phase delays and phase advances were observed in both mPer1 and mPer2 mutant mice. These results are not consistent with the hypothesis that mPER1 and mPER2 play necessary and nonoverlapping roles in mediating the effects of light on the circadian clock.
In Vitro Evaluation of 3T3 and MDBK Cells Attachment and Proliferation on Collagen and Fibronectin Immobilized Nonwoven Polylactide Matrices
Authors: Ayhan Hakan , Ayhan Fatma
Published: April 2003

Fibroblast-like, 3T3 (Mouse Swiss Albino) and epithelial-like MDBK (Madine Darby Bovine Kidney) cells were selected as model cell lines and the adhesion of these cells on nonwoven poly DL-lactide (PDLLA) matrices were investigated. PDLLA was synthesized by ring-opening polymerization of DL-lactide. Nonwoven PDLLA matrices were prepared by an extrusion/winding process. Surface modification of these matrices was achieved by glow-discharge treatment, which was followed by glutaraldehyde incorporation. Biologically modification was performed by immobilization of collagen and/or fibronectin for cell attachment and proliferation. Adhesion values of fibroblast-like and epithelial-like cells after incubation for 2 h was 90 and 85% of initial cells, respectively. The 3T3 cells grown on PDLLA, after 11 days of incubation, was 9 105 cells while the control group was 1.2 106 cells. MDBK cells grown on the same polymeric matrices were determined to be 1.5 106 cells and 1.8 106cells for the control group. These results indicate that biodegradable nonwoven PDLLA matrices can be used for adhesion and proliferation of primary cell cultures and that implants of polymer-cells composites can be used in wound healing. An important advantage of these matrices is that a second surgical operation is not necessary to remove the implant due to the biodegradation of polymer in tissue.
Effect of the Polylysine Based Polymeric Polypeptides on the Growth and Chemotaxis of Tetrahymena Pyriformis
Authors: Szabö Rita , Mezö Gábor , Hudecz Ferenc , Köhidai Lászlö
Published: April 2003

Polylysine based branched polypeptides represents a group of biocompatible polymers that could be utilized as macromolecular carriers for drugs, epitopes or reporter molecules. Ten polymers with different character (amino acid composition and charge properties) were prepared: polypeptides with single amino acid in the branches (poly[Lys(Xi)]), X = His, Pro or Glu; and polymers possessing oligo[DL-alanine] side chains only (poly[Lys(DL-Alam) (AK) or with an additional amino acid residue poly[Lys(Xi-DL-Alam)] (XAK), where X = Ser (SAK), Thr (TAK), Glu (EAK), acetyl-Glu (Ac-EAK) or succinyl-Glu (Succ-EAK). were investigated. The concentration of these compounds influence the chemotaxis and survival of eukaryotic unicellular model organism, Tetrahymena pyriformis GL. Two types of experiments were performed. First the polymer induced chemoattractant/chemorepellent response of Tetrahymena cells were tested, then chemotactic selection experiments were performed. The chemotactic responses elicited by the polymers were dependent not only on chemical properties (composition, charge and the length of the side chain) of the compounds, but also on their concentration. Based on these results, the polymers were grouped as full-chemoattractant expressing this behavior in the full concentration range investigated (HiK), full-chemorepellent (EiK and Ac-EAK) and partial chemoattractant/chemorepellent with concentration dependent activity (PiK, EAK and Succ-EAK).
Influenza in the Intensive Care Unit
Authors: Oliveira Eduardo C. , Lee Burton , Colice Gene L.
Published: April 2003

Influenza remains an important epidemic viral infection. Thousands of deaths occur and billions of dollars are spent each year with influenza-related illnesses. Morbidity and mortality are largely attributed to respiratory complications that may require intensive care unit (ICU) admission. Medical and neonatal ICUs, transplant units, chroniccare wards, and nursing homes are at increased risk for nosocomial outbreaks of influenza, which are characterized by abrupt onset and rapid spread. In this article, the authors review the current concepts, recent advances, and management strategies in influenza-associated pneumonia. Pertinent issues to the critical care practitioner are discussed in detail.
Hemodynamic Consequences of Heart-Lung Interactions
Authors: Steingrub Jay S. , Tidswell Mark , Higgins Thomas L.
Published: April 2003

The management of critically ill patients requires a fundamental understanding of cardiopulmonary interactions associated with mechanical ventilation. The hemodynamic changes due to ventilation are a result of changes in lung volume and intrathoracic pressure (ITP) and can occur during spontaneous or positive pressure ventilation despite constant tidal volumes. Pulmonary vascular resistance (PVR) and mechanical heart-lung interactions play prominent roles in determining the hemodynamic response to mechanical ventilation. Lung inflation alters PVR and right ventricular wall tension and, at high lung volume, mechanically limits cardiac volumes. The authors will consider the mechanisms of the effects of ITP on the pulmonary arterial and venous branches. These effects will aid in understanding the complex interactions between ventilation and right and left ventricular pressures and volumes, as well as the influence of lung inflation pressure on ventricular interdependence.
Vena Caval Filters: A Review for Intensive Care Specialists
Authors: Streiff Michael B.
Published: April 2003

Venous thromboembolism (VTE) is a common complication among patients in the intensive care unit. While anticoagulation remains standard therapy, vena caval filters are an important alternative when anticoagulation is contraindicated. To determine the safety and efficacy of vena caval filters in the treatment of VTE, a comprehensive review of the English-language medical literature was performed. Except for one randomized controlled trial, the literature supporting the use of vena caval filters consists almost exclusively of case series, which in many instances are limited by incomplete and short follow-up. While case series suggest that filters function effectively in the prevention of pulmonary embolism (2%-4% symptomatic pulmonary embolism [PE], fatal PE < 2%), recent higher quality studies indicate that filters may not provide significant additional protection to that provided by anticoagulation alone. Furthermore, filters are associated with a 2- fold increase in the incidence of recurrent DVT. Until randomized comparative studies are available, the safety and efficacy of all the available devices should be considered to be roughly equivalent. Since filters do not inhibit continued clot formation, all filter patients should receive anticoagulation for durations appropriate for their thrombotic disorder. Although extended anticoagulation may prevent thrombotic complications associated with filter placement, this strategy has yet to be experimentally tested. While many additional indications for vena caval filter use have been proposed (VTE in cancer patients, PE prophylaxis in trauma patients, etc), well-designed clinical trials demonstrating their efficacy in these situations are lacking. Further development of temporary/retrievable filters, which offer the potential to avoid the long-term complications of permanent filters, should be a research priority. Until additional data are available, vena caval filters should generally be restricted to patients with VTE who cannot receive anticoagulation.
Adsorption of Bovine Serum Albumin onto Surface-Modified Polyhydroxyethyl Methacrylate Beads
Authors: Pulat Mehlika , Memiş Elif , Gümüşderelioğlu Menemşe
Published: April 2003

The adsorption of bovine serum albumin (BSA) onto poly(2-hydroxyethyl methacrylate) (PHEMA) beads modified by using the pair of hexamethylene diisocyonate–suberic acidbis-N-hydroxy succinimide has been studied as a function of protein concentration and adsorption time. The adsorption studies were carried out in phosphate buffer solution (PBS) at pH = 7.4. The isotherm data have been analysed using the Langmuir model and the adsorption parameters Q0 and b were calculated. It is determined that the adsorbed amount of BSA increases by the increase of the adsorption time and BSA concentration until a certain value. PHEMA beads were characterized by using FTIR spectra and SEM analysis. The adsorption of BSA onto PHEMA beads were clearly observed from SEM micrographs. The swelling tests of the beads were performed at 37°C in PBS.
Effects of Enzymatic Treatments on the Biomechanical Properties of Screws Made of Bone
Authors: Actis A. B. , Obwegeser J. A. , Bertolotto P.
Published: April 2003

Nowadays, bone tissue employed to manufacture screws used as osteosynthesis material is obtained from organ donors. But in different medical fields there is an increasing need to use xenogenic grafts and implants, which still imply risks of transmission of some diseases and antigenicity.

Two different autoclaving programs (A1, A2) and an alternative to reduce the antigenicity of screws made of xenogenic bone based on enzymatic treatment are analyzed from a biomechanical point of view.

128 screws made of bovine femur bone were employed. Some of them were partially demineralized with 0.6 N HCl, enzymatically digested with collagenase (specific) and pepsin (nonspecific) and then autoclaved. The specimens were subjected to tension, shear and screw torque tests and histologically evaluated.

Compared to A1, A2 sterilization method (134°C but higher vacuum and longer time) considerably reduced the mechanical strength of specimens. The enzymatic digestion, expected to reduce antigenicity, did not affect the screw superficial structure and would not modify the bone biomechanical properties per se, but maybe because of the association with autoclaving and partial demineralization.
Oral Insulin – a Perspective
Authors: Raj N. K. Kavitha , Sharma Chandra P.
Published: April 2003

Diabetes mellitus is generally controlled quite well with the administration of oral medications or by the use of insulin injections. The current practice is the use of one or more doses, intermediate or long acting insulin per day. Oral insulin is a promising yet experimental method providing tight glycemic control for patients with diabetes. A biologically adhesive delivery systems offer important advantage over conventional drug delivery systems. The engineered polymer microspheres made of erodable polymer display strong adhesive interactions with gastrointestinal mucus and cellular lining can traverse both the mucosal epithelium and the follicle associated epithelium covering the lymphoidtissue of Peyer’s patches. Alginate, a natural polymer recovered from seaweed is being developed as a nanoparticle for the delivery of insulin without being destroyed in the stomach. Alginate is infact finding application in biotechnology industry as thickening agent, a gelling agent and a colloid stabilizer. Alginate has in addition, several other properties that have enabledit to be usedas a matrix for entrapment and for the delivery of a variety of proteins such as insulin andcells. These properties include: a relatively inert aqueous environment within the matrix; a mildroom temperature encapsulation process free of organic solvents; a high gel porosity which allows for high diffusion rates of macromolecules; the ability to control this porosity with simple coating procedures and dissolution and biodegradation of the system under normal physiological conditions.
The Effects of Impact Fees on the Price of Housing and Land: a Literature Review
Authors: Evans-Cowley Jennifer S. , Lawhon Larry L.
Published: April 2003

Since the 1970s, development impact fees have emerged as a way to pass the cost of new infrastructure to the development community. Although development impact fees intend to transfer the burden of infrastructure provision to the developer, it is widely believed that the homebuyer ultimately absorbs the cost through inflated housing and land prices. This article examines the planning practice implications of development impact fees on housing and land prices. The review of the literature suggests that impact fees contribute to housing price infation in communities where there are no reasonable housing substitutes and that tax burden and infrastructure enhancements are capitalized into the price of home and land.
Intractability in Environmental Disputes: Exploring a Complex Construct
Authors: Campbell Marcia Caton
Published: April 2003

Planners are finding it increasingly helpful to use conflict resolution techniques to manage conditions of uncertainty and conflict endemic to environmental and land use planning, and public policy making. Some disputes in these areas, however, are by their very nature unusually resistant to resolution, rendering them especially difficult for planners to manage without significant mediation training and skill. By exploring the literature on dispute intractability, this article maps for planners characteristics of intractable environmental, land use, and public policy disputes and discusses the usefulness of the transformative mediation approach for managing intractable disputes. Empirical research on dispute intractability, now in its nascent stages, could be productively applied by planners in making conflict assessments and applying dispute resolution techniques in planning practice.
Rethinking Empowerment Theory Using a Feminist Lens: The Importance of Process
Authors: Carr E. Summerson
Published: April 2003

This article highlights the importance of social, historical, and political context when theorizing empowerment and “maps” empowerment as a cyclical, rather than a linear, process. Synthesizing important perspectives in feminist thought and empowerment theory, it proposes understandings of positionality, conscientization, and social transformation that are meant to inform empowerment-oriented, feminist social work practice.