The chronobiology of the brushtail possum, Trichosurus vulpecula (Marsupialia:Phalangeridae): tests of internal and external control of timing

1999 ◽  
Vol 47 (6) ◽  
pp. 579 ◽  
Author(s):  
P. A. Herbert ◽  
R. D. Lewis
Keyword(s):  
Internal Control ◽  
Internal Clock ◽  
External Control ◽  
Constant Darkness ◽  
Brushtail Possum ◽  
Dark Phase ◽  
Trichosurus Vulpecula ◽  
Direct Response ◽  
Natural Behaviour ◽  
Free Running

The chronobiology of the brushtail possum (Trichosurus vulpecula) was investigated in a vivarium and in light-controlled cabinets to determine what controls the timing of natural patterns of activity and rest. It is proposed that the timing of natural behaviour of the possum is not regulated entirely by direct response to environmental factors, but that it may have an element of internal control. Unless perturbed by wind and/or rain, the onset of activity is precisely timed each day, beginning as light intensity declines following sunset. In tests of an internal clock hypothesis, possums in constant darkness exhibited free-running circadian rhythms of activity with periods initially slightly shorter than 24 h, spontaneously reducing to c.22 h 40 min after c. 40 days. The internal rhythm of the possum could be entrained by 24-h light/dark cycles with activity initiated at the onset of the dark phase. We propose that the timing of the onset of natural behaviour of the possum is controlled through the output of a circadian clock that may be modulated by direct responses to wind and rain.

Circadian and estrous cycle-dependent variations in blood pressure and heart rate in female rats

1994 ◽  
Vol 267 (5) ◽  
pp. R1250-R1256 ◽  
Author(s):  
H. Takezawa ◽  
H. Hayashi ◽  
H. Sano ◽  
H. Saito ◽  
S. Ebihara
Keyword(s):  
Heart Rate ◽  
Estrous Cycle ◽  
Female Rats ◽  
Constant Darkness ◽  
Dark Phase ◽  
Daily Rhythms ◽  
Abrupt Decrease ◽  
Internal Phase ◽  
Free Running ◽  
Cycle Dependent

To determine whether cardiovascular functions are controlled by the endogenous circadian system and whether they change with the estrous cycle in female rats, we measured mean arterial pressure (MAP), heart rate (HR), and spontaneous activity (ACT) of female rats using an implantable radiotelemetry device and a computerized data-collecting system. Under a 12:12-h light-dark (LD) cycle, these parameters exhibited daily rhythms that were entrained to the photic cycle. The patterns of the daily rhythms varied with estrous cycles, and variations were particularly marked in the proestrous stage. During the dark period of this stage, ACT levels were significantly higher, but HR was significantly lower than in other stages. Although the peak MAP occurred within 2 h after the onset of the dark phase in three of the estrous stages, it occurred around midnight in the proestrous stage. Such estrous cycle-dependent variations were eliminated by ovariectomy. The implantation of 17 beta-estradiol produced a gradual increase in MAP and an abrupt decrease in HR. During constant darkness, all three parameters were free running, maintaining the same internal phase relationships with each other as during LD cycles. These results indicate that daily variations in these parameters were controlled by the endogenous circadian oscillating system, that they vary with the estrous cycle in female rats, and that estrogen may be responsible for these estrous cycle-dependent variations.

A circadian rhythm of behavioural thermoregulation in a freshwater gastropod, Helisoma trivolis

1980 ◽  
Vol 58 (11) ◽  
pp. 2152-2155 ◽  
Author(s):  
Martin Kavaliers
Keyword(s):  
Circadian Rhythm ◽  
Constant Darkness ◽  
Dark Phase ◽  
Behavioural Thermoregulation ◽  
Dark Cycle ◽  
Preferred Temperature ◽  
Temperature Selection ◽  
Freshwater Gastropod ◽  
Free Running ◽  
Maximum Temperatures

The behaviour of the aquatic gastropod Helisoma trivolis was examined in a thermal gradient. Under a 12 h light: 12 h dark cycle gastropods displayed a diel rhythm of preferred temperature selection. Maximum temperatures (21–22 °C) were selected during the dark phase and minimum temperatures (17–18 °C) were selected during the light phase of the light–dark cycle. Under constant darkness temperature selection continued as an endogenous free-running circadian rhythm of behavioural thermoregulation.

Impact of the Locus of Causality and Internal Control on the Social Utility of Causal Explanations

2010 ◽  
Vol 69 (3) ◽  
pp. 173-179 ◽  
Author(s):  
Samantha Perrin ◽  
Benoît Testé
Keyword(s):  
Internal Control ◽  
Three Dimensions ◽  
Social Utility ◽  
External Control ◽  
Job Interview ◽  
Locus Of Causality ◽  
Causal Explanations ◽  
Professional Success ◽  
The Social ◽  
Different Types

Research into the norm of internality ( Beauvois & Dubois, 1988 ) has shown that the expression of internal causal explanations is socially valued in social judgment. However, the value attributed to different types of internal explanations (e.g., efforts vs. traits) is far from homogeneous. This study used the Weiner (1979 ) tridimensional model to clarify the factors explaining the social utility attached to internal versus external explanations. Three dimensions were manipulated: locus of causality, controllability, and stability. Participants (N = 180 students) read the explanations expressed by appliants during a job interview. They then described the applicants on the French version of the revised causal dimension scale and rated their future professional success. Results indicated that internal-controllable explanations were the most valued. In addition, perceived internal and external control of explanations were significant predictors of judgments.

scholarly journals Location, Location, Location: The Role of Objective Neighborhood Characteristics for Perceptions of Control

Gerontology ◽  
2021 ◽  
pp. 1-10
Author(s):  
Johanna Drewelies ◽  
Peter Eibich ◽  
Sandra Düzel ◽  
Simone Kühn ◽  
Christian Krekel ◽  
...  
Keyword(s):  
Internal Control ◽  
Reference Model ◽  
Self Report ◽  
Control Beliefs ◽  
External Control ◽  
Neighborhood Characteristics ◽  
Linear Regression Models ◽  
Residential Areas ◽  
Age Related ◽  
Self Report Data

<b><i>Introduction:</i></b> Control beliefs can protect against age-related declines in functioning. It is unclear whether neighborhood characteristics shape how much control people perceive over their life. This article studies associations of neighborhood characteristics with control beliefs of residents of a diverse metropolitan area (Berlin, Germany). <b><i>Methods:</i></b> We combine self-report data about perceptions of control obtained from participants in the Berlin Aging Study II (<i>N</i> = 507, 60–87 years, 51% women) with multisource geo-referenced indicators of neighborhood characteristics using linear regression models. <b><i>Results:</i></b> Findings indicate that objective neighborhood characteristics (i.e., unemployment rate) are indeed tied to perceptions of control, in particular, how much control participants feel others have over their lives. Including neighborhood characteristics in part doubled the amount of explained variance compared with a reference model covarying for demographic characteristics only (from <i>R</i><sup>2</sup> = 0.017 to <i>R</i><sup>2</sup> = 0.030 for internal control beliefs; <i>R</i><sup>2</sup> = 0.056 to <i>R</i><sup>2</sup> = 0.102 for external control beliefs in chance; <i>R</i><sup>2</sup> = 0.006 to <i>R</i><sup>2</sup> = 0.030 for external control beliefs in powerful others). <b><i>Discussion/Conclusion:</i></b> Findings highlight the importance of access to neighborhood resources for control beliefs across old age and can inform interventions to build up neighborhood characteristics which might be especially helpful in residential areas with high unemployment.

Effectiveness of a Problem-Solving Training Program

1995 ◽  
Vol 76 (2) ◽  
pp. 507-514 ◽  
Author(s):  
Johan W. Wege ◽  
André T. Möller
Keyword(s):  
Problem Solving ◽  
Training Program ◽  
Undergraduate Students ◽  
Internal Control ◽  
Self Efficacy ◽  
Group Analysis ◽  
External Control ◽  
Problem Solving Skills ◽  
Control Orientation ◽  
Problem Solvers

The relationship between problem-solving efficiency, defined in terms of the quality of alternative soludons selected, and measures of behavioral competence (self-efficacy and locus of control) was investigated as well as the effectiveness of a problem-solving training program. Subjects were 29 undergraduate students assigned to an effective ( n = 16) and an ineffective ( n = 13) problem-solving group. Analysis indicated that the ineffective problem-solvers appraised their problem-solving skills more negatively and reported low self-efficacy expectations and an external control orientation. Problem-solving training led to improved general self-efficacy expectancies, greater confidence in problem-solving, a more internal control orientation, and improved problem-solving skills. These improvements were maintained at follow-up after two months.

scholarly journals Preovulatory follicle development and ovulation in the brushtail possum (Trichosurus vulpecula) monitored by repeated laparoscopy

Reproduction ◽  
1997 ◽  
Vol 110 (2) ◽  
pp. 361-370 ◽  
Author(s):  
J. L. Crawford ◽  
G. H. Shackell ◽  
E. G. Thompson ◽  
B. J. McLeod ◽  
P. R. Hurst
Keyword(s):  
Brushtail Possum ◽  
Follicle Development ◽  
Trichosurus Vulpecula ◽  
Preovulatory Follicle

Gonadal hormones organize and modulate the circadian system of the rat

1981 ◽  
Vol 241 (1) ◽  
pp. R62-R66 ◽  
Author(s):  
H. E. Albers
Keyword(s):  
Testosterone Propionate ◽  
Wheel Running ◽  
Activity Rhythm ◽  
Gonadal Hormones ◽  
Circadian System ◽  
Female Rats ◽  
Constant Darkness ◽  
Before And After ◽  
Free Running ◽  
Free Running Period

The circadian wheel-running rhythms of gonadectomized adult male, female, and perinatally androgenized female rats, maintained in constant darkness, were examined before and after implantation of Silastic capsules containing cholesterol (C) or estradiol-17 beta (E). The free-running period of the activity rhythm (tau) before capsule implantation tended to be shorter in animals exposed to perinatal androgen. Administration of C did not reliably alter tau in any group. E significantly shortened tau in 100% of females injected with oil on day 3 of life. In females, injected with 3.5 micrograms testosterone propionate on day 3, and males, E shortened or lengthened tau, with the direction and magnitude of this change in tau inversely related to the length of the individual's pretreatment tau. These data indicate that the presence of perinatal androgen does not eliminate the sensitivity of the circadian system of the rat to estrogen, since estrogen alters tau in a manner that depends on its pretreatment length.

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