The relationship of resiliency to decision making and risk behaviors of cancer-surviving adolescents.

Adolescents with a history of cancer frequently engage in risk behaviors. The purpose of this correlational study was to explore factors that affect decision making and risk behaviors (smoking, alcohol use, and illicit drug use) of cancer-surviving adolescents. A sample of 52 teen survivors participated at two cancer centers. In addition to a medical record review and IQ testing, several psychosocial measures were administered in a semistructured interview with the teen survivor. Three antecedent factors (cognitive function, resiliency, and role modeling of risk behaviors by parents and peers) were examined in a hierarchical regression model to predict decision making. These same factors, with an additional mediating variable (decision making), were examined in a hierarchical logistic regression model to predict risk behaviors in teen survivors. In the decision-making model, adjusted for demographic covariates, resiliency was a marginally significant predictor of decision making. As non-resiliency increases, quality of decision making may decrease for teen survivors. In the model to predict risk behaviors, four factors (cognitive function, resiliency, role modeling, and decision making) were added to the basic model, controlling for the same covariates. Resiliency and decision making were highly significant predictors of one or more risk behaviors. Non-resilient teen survivors with poor-quality decision making are more likely to engage in risk behaviors of substance use and need intervention that is aimed at improving decision-making skills to reduce these behaviors.

Corticosterone and nocturnal torpor in the rufous hummingbird (Selasphorus rufus).

Three experiments were designed to investigate whether corticosterone (CORT), known to have a role in restoration of energy homeostasis, regulates nocturnal torpor, an energy conservation state used by some small mammals and birds to offset environmental challenges to energy balance. In two experiments, one during autumn migration and one during early spring molt, captive rufous hummingbirds (Selasphorus rufus) were fed control and dilute (85% strength) nectar on alternate days. In migratory birds, torpor occurred more frequently over all, and nectar dilution resulted in increased torpor duration and increased concentration of CORT in evening but not midday cloacal fluid (CF) samples. In molting birds, torpor occurred infrequently on both control and food dilution days, but, although there was a significant increase in evening CF CORT on food dilution days, torpor duration did not increase significantly in response and there was no correlation between torpor duration and CF CORT at either time of day. Daily CF CORT patterns showed an increase from midday to evening during migration, but the reverse pattern during the molt. In a third experiment, CORT administered in the nectar elevated the use of torpor and depressed food intake. The results of these three experiments support the hypothesis that CORT is involved in the regulation of torpor, but suggest that some feature of the CORT signal other than concentration per se may be required to fully explain seasonal changes in the relations among energy challenge, CORT, and nocturnal torpor in hummingbirds.

Noninvasive methods for measuring and manipulating corticosterone in hummingbirds.

The adrenocortical response to stress has been shown to be important in energy management of vertebrates. Although hummingbirds (Trochilidae) are useful models for studying energy balance, they are not amenable to traditional methods of studying hormones. In this study we report noninvasive methods for measuring and manipulating corticosterone (CORT), the principal stress glucocorticoid in birds. CORT was measured in cloacal fluid (CF) collected from unrestrained rufous hummingbirds (Selasphorus rufus). We demonstrate that CF CORT can be measured by radioimmunoassay without extraction. CF creatinine, when used as a reference measure for CF CORT, corrects for changes in hydration state. As in other birds, CORT in both plasma and CF rose in response to capture and handling stress and decreased after the termination of that stress, except that changes in CF concentration were delayed with respect to changes in plasma. When CORT, complexed with cyclodextrin to improve solubility, was added to artificial nectar, CF CORT concentrations changed in a predictable, dose-dependent fashion. Measuring CORT in CF is advantageous because it allows frequent and repeated sampling without itself provoking a detectable stress response and because baseline samples need not be obtained within the very short time between the onset of a stressor and the appearance of CORT in the plasma, as is true for blood sampling. Administration of exogenous CORT in the food offers a noninvasive, nonstressful, temporally sensitive method for experimentally manipulating hormone levels in an avian model that has already been used extensively for studies of energetics.

Information age testing: making rigorous exams fun to write and easy to grade.

This essay discusses methods by which an exam writer can achieve three objectives: 1) producing questions that test a student's understanding, defined as the ability to apply knowledge in a novel context; 2) writing questions that require minimal grading time; and 3) keeping current and excited about the field, which is critical for transmitting personal enthusiasm to students. Included are descriptions of practical, time-saving methods for processing and filing examination material; ways to use readily available databases for quickly generating rigorous, interesting questions, with examples of questions generated in this way; suggestions for structuring questions so that they are easily graded; and general advice for preparing students to take this kind of examination.

Photic entrainment of circannual rhythms in golden-mantled ground squirrels: role of the pineal gland.

Entrainment of circannual rhythms of body mass and reproduction was monitored for 3 years in female golden-mantled ground squirrels maintained in a simulated natural photoperiod. Both pinealectomized and pineal-intact squirrels generated circannual rhythms of body mass and estrus, but only the intact animals entrained these rhythms to a period of 365 days. In the second and third years after treatment, the period of the body mass rhythm was significantly shorter than 365 days for pinealectomized squirrels, and variance in tau among these animals was significantly greater than for intact squirrels. A similar pattern was evident in the rhythm of reproduction, which was phase-disrupted in pinealectomized squirrels but entrained in intacts. Seasonal changes in duration of nocturnal melatonin secretion by the pineal appear to be necessary to produce phase-delays required to entrain the circannual clock to a period of 12 months.

Estradiol phase shifts circannual body mass rhythms of male ground squirrels.

Gonadectomized male golden-mantled ground squirrels (Spermophilus lateralis) were implanted with estradiol benzoate (EB)-filled or empty capsules. Body mass was monitored before, during, and for at least 1 yr after hormone treatment. EB treatment during the mass-gain phase of the annual cycle significantly decelerated increases in body mass; the period of the circannual rhythm (CAR) of body mass was 54 days longer in EB- than blank-treated squirrels. Hormone treatment during the mass-loss phase accelerated mass loss; although this effect only approached statistical significance, some phase markers of the CAR were significantly advanced in subsequent cycles. We conclude that, as in females, estradiol affects the waveform of the CAR of males differently at different phases of the circannual cycle. Sexual differentiation does not eliminate responsiveness of CARs of squirrels to estradiol; sex differences, if any, are subtle rather than absolute and, in this respect, differ from circadian rhythms.

Time-dependent thresholds for torpor initiation in the rufous hummingbird (Selasphorus rufus).

Three models for torpor initiation were tested in rufous hummingbirds (Selasphorus rufus) during moult, when these birds appear to avoid the use of torpor. In model 1, the level of energy reserves at which torpor is initiated (the "threshold") remains constant throughout the night. In model 2, the threshold declines throughout the night, at a constant rate equivalent to the rate at which energy reserves are depleted during torpor. In model 3, the threshold declines at a rate equivalent to the rate of energy reserve depletion during torpor for most of the night, but at a higher rate (corresponding to the rate of energy expenditure during normothermia) during the final 2 h of the night, when these birds are usually normothermic. Model 1 predicts the most frequent and longest bouts of torpor, whereas model 3 predicts the fewest and shortest bouts. To determine the thresholds for each of 12 birds, food supply was manipulated to induce entry into torpor at different times on successive nights. Threshold slopes matched the predictions of model 3 most closely. Calculations comparing observed incidence of torpor with the predictions of model 1 show that the actual, time-dependent threshold for torpor initiation resulted in a 72% reduction in the number of torpor bouts compared with the number of torpor bouts that should have been initiated by a constant threshold. The advantage of a time-dependent threshold is that, although torpor is initiated when needed to prevent energy reserves from falling below a critical level, the amount of time spent in torpor can be minimized.(ABSTRACT TRUNCATED AT 250 WORDS)