Differential effects of empty and filled intervals on duration estimation by pigeons: tests of an attention-sharing explanation

Pigeons were trained in a within-subjects design to discriminate durations of an empty interval and a filled interval. Even when different stimuli were used to mark empty intervals and to signal filled intervals, pigeons judged empty intervals to be longer than equal-length filled intervals. This timing difference was not a result of pigeons timing marker duration on empty interval trials. Increasing marker duration did not produce an overestimation of the empty time intervals. It was suggested that this timing difference could be due to a reduction in attention to temporal processing on filled interval trials when visual stimuli are used. Consistent with this hypothesis, it was found that empty intervals were judged longer than filled intervals when testing occurred in a darkened test room, but not when the test room was illuminated. In addition, no timing difference was observed when different auditory stimuli were used as markers for empty intervals and as signals for filled intervals.     

Opposing effects of Wnt and MAPK on BMP/Smad signal duration

Signaling downstream of BMP receptors relies on activated nuclear Smad proteins. Recent studies, one of which is published in the November 30 issue of Cell, shed light on a mechanism that balances inputs from both activated MAPK and Wnt pathways to regulate the proteasomal degradation of Smad1 and thus modulate the extent of BMP signaling.     

The effects of heat-induced pain on the detectability,discriminability, and sensation magnitude of vibrotactile stimuli

The effects of heat-induced pain on absolute thresholds, sensation magnitudes and amplitude-difference thresholds were measured at 10 and 100 Hz. Consistent with previous results, heat-induced pain elevated the absolute thresholds by approximately 8.0 dB and lessened the magnitudes of tactile sensations during pain as compared to the non-painful condition. In contrast to these effects, the discriminability of change in the intensity of the vibrotactile stimuli was unaffected by the presence of pain indicating that the effect of pain on tactile sensations is more likely due to sensory rather than cognitive processes (i.e., attention) and that the mechanisms underlying tactile sensitivity as compared to discriminability are different.     

The effects of heat-induced pain on the detectability, discriminability, and sensation magnitude of vibrotactile stimuli

The effects of heat-induced pain on absolute thresholds, sensation magnitudes and amplitude-difference thresholds were measured at 10 and 100 Hz. Consistent with previous results, heat-induced pain elevated the absolute thresholds by approximately 8.0 dB and lessened the magnitudes of tactile sensations during pain as compared to the non-painful condition. In contrast to these effects, the discriminability of change in the intensity of the vibrotactile stimuli was unaffected by the presence of pain indicating that the effect of pain on tactile sensations is more likely due to sensory rather than cognitive processes (i.e., attention) and that the mechanisms underlying tactile sensitivity as compared to discriminability are different.     

Training delays reduce the choose-short effect with keylight, but not with food, duration samples in pigeons

Pigeons were trained to match 2- and 8-s food samples. The delay on training trials was either 0s (group 0sF), 5s (group 5sF), or varied between 2 and 8s (M=5s, group 5sV). Testing at a delay that exceeded the training delay by 15s in each group revealed a robust choose-short effect in each group. The same pigeons then reacquired a previously trained matching task involving 2- and 8-s keylight samples. Different comparison stimuli were used on food-sample and keylight-sample trials. The delay on training trials was the same on both food- and keylight-sample trials. Extended-delay testing revealed a robust choose-short effect in all three groups when the durations were conveyed by food presentations, but only group 0sF revealed a choose-short effect when the durations were conveyed by keylight presentations. Hence, training with a nonzero delay, whether fixed or variable, reduces the choose-short effect with keylight durations but not with food durations. It was concluded that at least some of the psychological processes mediating performance differ as a function of the event that conveys the duration.     

Radiation-induced mitotic delay: duration, dose and cell position dependence in the crypts of the small intestine in the mouse

The cells of the proliferative compartment in the crypt of the small intestine undergo a step by step differentiation and/or maturation from stem cells to the functional cells on the villi. The consequent hierarchical organization of the proliferative cell population can be related to the actual position of cells within the crypt. The stem cells are found near the bottom of the crypt with the more mature cells occurring at increasingly higher positions. The sensitivity of proliferative cells in the crypt of small intestine to radiation-induced mitotic delay was investigated at each position within the crypt. Using the stathmokinetic method (vincristine accumulation), the following were noted. The yield of mitotic figures 3 h immediately after irradiation showed a strong cell position dependence with the cells at the base of the crypt being most inhibited and those at the top of the proliferative compartment least affected. The mitotic yields were largely unaffected for the first 15 min suggesting that there is a transition point (Tp) for radiosensitivity which is located about 15 min before metaphase for all crypt cells. Cells located less than 15 min from metaphase are unaffected while those more than 15 min from metaphase are inhibited from further cell cycle progression. After this initial delay all proliferative cells were inhibited in their progression through G2 but some recovered more quickly than others. The ratio of the time of division delay (Td) in stem cells to that in cells at the top of the proliferative compartment was about 3:1. In absolute values Td after 1.0 Gy was about 1 h and 2.8 h, for cells at the top of the crypt and at the base, respectively. After 2.5 Gy the corresponding values were less than 3 h and between 5 and 6 h for the mid-crypt and crypt base respectively. There is thus a dependence on dose for the duration of the mitotic inhibition which for the cells at the top of the crypt is similar to the widely quoted average value 1 h per Gy, but the duration depends strongly on cell position. Thus not all proliferative cells respond in the same way. The duration is shorter the closer the proliferative cells are to their last cell division in the proliferative hierarchy in the crypt and longest for cells situated where the stem cells are to be expected.     

Independent effects of social position and parity on body mass index among Polish adult women

This study evaluated the strength of the independent effects of social position (expressed by educational level) and number of childbirths on body mass index (BMI) variation of Polish adult females. The material comprised 2045 pre-menopausal women aged 35-50, who were healthy and occupationally active inhabitants of the city of Wroc?aw, Lower Silesia, Poland. Two-way analysis of variance (ANOVA) revealed that both educational level (F = 34.7; p = 0.0001) and parity (F = 5.6; p = 0.001) exerted independent significant effects on BMI. The mean BMI of women who had attended basic vocational or trade school at the very most (27.0 kg/m2) was greater than that of women who had completed secondary school education or had graduated from university (25.3 kg/m2). However, it is worthy of note that there were no social differences in BMI values between childless women. Nevertheless, an increasing number of childbirths was essentially related to increasing female BMI in each social group, and this tendency was most marked among women of lower social position. Regardless of educational level, the highest prevalence of obesity (BMI exceeding 30 kg/m2) was found among females with at least three children (15.6%, and 26.4% of women from higher or lower social groups, respectively).     

Flight effects on plasma glucose, lactate, catecholamines and corticosterone in homing pigeons

Significant increase in the circulating levels of glucose, lactate, adrenaline (A) and noradrenaline (NA) was observed in homing pigeons after a flight of 48 km, lasting 60-80 min. There was, however, no change in plasma corticosterone concentrations. The increase in lactate has been attributed mainly to the activity of the white glycolytic fibres in the flight muscles. The increase in A and NA indicated increased sympathetic activity. It is suggested that the flight-induced increase in A stimulated the release of glucagon which could account for the increase in plasma glucose. The lack of any increase in plasma corticosterone implied that the birds were not under any serious stress during the flight and that these results represent the normal changes that may be expected in pigeons during a free flight of the specified distance and duration.     

Discrimination of cartoons and photographs in pigeons: effects of scrambling of elements

Four groups of pigeons were trained on four visual discrimination tasks using people photographs, pigeon photographs, cartoons of people, and cartoons of pigeons. After completion of the discrimination, the subjects were tested with new stimuli in the same stimulus categories but never used during the training, and scrambled stimuli in which elements of the original stimulus were spatially randomized. The subjects showed generalization to the new stimuli except for the people cartoons. When scrambled stimuli were presented, the subjects showed suppression of responding to the photographs but not to the people cartoon. These results suggest that the pigeons recognized both the elements and spatial arrangement of the photographs but ignored the spatial arrangement of the human cartoons.     

Object discrimination by pigeons: effects of object color and shape

Can nonhuman animals attend to visual stimuli as whole, coherent objects? We investigated this question by adapting for use with pigeons a task in which human participants must report whether two visual attributes belong to the same object (one-object trial) or to different objects (two-object trial). We trained pigeons to discriminate a pair of differently colored shapes that had two targets either on a single object or on two different objects. Each target equally often appeared on the one-object and two-object stimuli; therefore, a specific target location could not serve as a discriminative cue. The pigeons learned to report whether the two target dots were located on a single object or on two different objects; follow-up tests demonstrated that this ability was not entirely based on memorization of the dot patterns and locations. Additional tests disclosed predominate stimulus control by the color, but not by the shape of the two objects. These findings suggest that human psychophysical methods are readily applicable to the study of object discrimination by nonhuman animals.     

Lymphocyte proliferation responses after exercise in men: fitness, intensity, and duration effects

This study investigated the effects of intensity and duration of exercise on lymphocyte proliferation as a measure of immunologic function in men of defined fitness. Three fitness groups--low [maximal O2 uptake (VO2max) = 44.9 +/- 1.5 ml O2.kg-1.min-1 and sedentary], moderate (VO2max = 55.2 +/- 1.6 ml O2.kg-1.min-1 and recreationally active), and high (VO2max = 63.3 +/- 1.8 ml O2.kg-1.min-1 and endurance trained)--and a mixed control group (VO2max = 52.4 +/- 2.3 ml O2.kg-1.min-1) participated in the study. Subjects completed four randomly ordered cycle ergometer rides: ride 1, 30 min at 65% VO2max; ride 2, 60 min at 30% VO2max; ride 3, 60 min at 75% VO2max; and ride 4, 120 min at 65% VO2max. Blood samples were obtained at various times before and after the exercise sessions. Lymphocyte responses to the T cell mitogen concanavalin A were determined at each sample time through the incorporation of radiolabeled thymidine [( 3H]TdR). Despite differences in resting levels of [3H]TdR uptake, a consistent depression in mitogenesis was present 2 h after an exercise bout in all fitness groups. The magnitude of the reduction in T cell mitogenesis was not affected by an increase in exercise duration. A trend toward greater reduction was present in the highly fit group when exercise intensity was increased. The reduction in lymphocyte proliferation to the concanavalin A mitogen after exercise was a short-term phenomenon with recovery to resting (preexercise) values 24 h after cessation of the work bout. These data suggest that single sessions of submaximal exercise transiently reduce lymphocyte function in men and that this effect occurs irrespective of subject fitness level.     

Modelling and simulation of signal transductions in an apoptosis pathway by using timed Petri nets

This paper first presents basic Petri net components representing molecular interactions and mechanisms of signalling pathways, and introduces a method to construct a Petri net model of a signalling pathway with these components. Then a simulation method of determining the delay time of transitions, by using timed Petri nets — i.e. the time taken in firing of each transition — is proposed based on some simple principles that the number of tokens flowed into a place is equivalent to the number of tokens flowed out. Finally, the availability of proposed method is confirmed by observing signalling transductions in biological pathways through simulation experiments of the apoptosis signalling pathways as an example.     

Independent effects of sleep duration and body mass index on the risk of a work-related injury: evidence from the US National Health Interview Survey (2004-2010)

Fatigue has been linked to adverse safety outcomes, and poor quality or decreased sleep has been associated with obesity (higher body mass index, BMI). Additionally, higher BMI is related to an increased risk for injury; however, it is unclear whether BMI modifies the effect of short sleep or has an independent effect on work-related injury risk. To answer this question, the authors examined the risk of a work-related injury as a function of total daily sleep time and BMI using the US National Health Interview Survey (NHIS). The NHIS is an in-person household survey using a multistage, stratified, clustered sample design representing the US civilian population. Data were pooled for the 7-yr survey period from 2004 to 2010 for 101 891 "employed" adult subjects (51.7%; 41.1?±?yrs of age [mean?±?SEM]) with data on both sleep and BMI. Weighted annualized work-related injury rates were estimated across a priori defined categories of BMI: healthy weight (BMI: <25), overweight (BMI: 25-29.99), and obese (BMI: ≥30) and also categories of usual daily sleep duration: <6, 6-6.99, 7-7.99, 8-8.99, and ≥9 h. To account for the complex sampling design, including stratification, clustering, and unequal weighting, weighted multiple logistic regression was used to estimate the risk of a work-related injury. The initial model examined the interaction among daily sleep duration and BMI, controlling for weekly working hours, age, sex, race/ethnicity, education, type of pay, industry, and occupation. No significant interaction was found between usual daily sleep duration and BMI (p =?.72); thus, the interaction term of the final logistic model included these two variables as independent predictors of injury, along with the aforementioned covariates. Statistically significant covariates (p ≤?.05) included age, sex, weekly work hours, occupation, and if the worker was paid hourly. The lowest categories of usual sleep duration (<6 and 6-6.9 h) showed significantly (p ≤?.05) elevated injury risks than the referent category (7-8 h sleep), whereas sleeping >7-8 h did not significantly elevate risk. The adjusted injury risk odds ratio (OR) for a worker with a usual daily sleep of <6 h was 1.86 (95% confidence interval [CI]: 1.37-2.52), and for 6-6.9 h it was 1.46 (95% CI: 1.18-1.80). With regards to BMI, the adjusted injury risk OR comparing workers who were obese (BMI: ≥30) to healthy weight workers (BMI: <25) was 1.34 (95% CI: 1.09-1.66), whereas the risk in comparing overweight workers (BMI: 25-29.99) to healthy weight risk was elevated, but not statistically significant (OR = 1.08; 95% CI: .88-1.33). These results from a large representative sample of US workers suggest increase in work-related injury risk for reduced sleep regardless of worker's body mass. However, being an overweight worker also increases work-injury risk regardless of usual daily sleep duration. The independent additive risk of these factors on work-related injury suggests a substantial, but at least partially preventable, risk.     

Prey from the eyes of predators: Color discriminability of aposematic and mimetic butterflies from an avian visual perspective

Predation exerts strong selection on mimetic butterfly wing color patterns, which also serve other functions such as sexual selection. Therefore, specific selection pressures may affect the sexes and signal components differentially. We tested three predictions about the evolution of mimetic resemblance by comparing wing coloration of aposematic butterflies and their Batesian mimics: (a) females gain greater mimetic advantage than males and therefore are better mimics, (b) due to intersexual genetic correlations, sexually monomorphic mimics are better mimics than female‐limited mimics, and (c) mimetic resemblance is better on the dorsal wing surface that is visible to predators in flight. Using a physiological model of avian color vision, we quantified mimetic resemblance from predators’ perspective, which showed that female butterflies were better mimics than males. Mimetic resemblance in female‐limited mimics was comparable to that in sexually monomorphic mimics, suggesting that intersexual genetic correlations did not constrain adaptive response to selection for female‐limited mimicry. Mimetic resemblance on the ventral wing surface was better than that on the dorsal wing surface, implying stronger natural and sexual selection on ventral and dorsal surfaces, respectively. These results suggest that mimetic resemblance in butterfly mimicry rings has evolved under various selective pressures acting in a sex‐ and wing surface‐specific manner.     

Exercise and blood lymphocyte subset responses: intensity, duration, and subject fitness effects

This study examined the effect of exercise intensity and duration on the percent blood lymphocytes in men of low [LF; maximal O2 uptake (VO2max) less than 50 ml.kg-1.min-1 and sedentary], moderate (MF; VO2max = 50-60 ml.kg-1.min-1 and recreationally active), and high (HF; VO2max greater than 60 ml.kg-1.min-1 and recent training history) fitness. Thirty healthy adult men (aged 20-31 yr) participated in four randomly ordered cycle ergometer rides: ride 1 (65% VO2max, 30 min), ride 2 (30% VO2max, 60 min), ride 3 (75% VO2max, 60 min), and ride 4 (65% VO2max, 120 min). Blood samples were drawn at various times before and after the exercise sessions. Lymphocyte subsets were determined by flow cytometry using monoclonal antibodies for total T (CD3+), T-helper (CD4+), and T-suppressor (CD8+) lymphocytes and for a subset of cells expressing a natural killer (NK) cell antigen (Leu7+). Plasma catecholamines were assayed to determine exercise stress. There were sharp reductions (P less than 0.01) in the percentage of pan-T and T-helper lymphocytes immediately after exercise across all fitness levels; the magnitude of this reduction was greatest after the highest intensity (ride 3) or longest duration (ride 4) work. In contrast, the absolute number of T and T-helper cells tended to increase after exercise and significantly so in the HF subjects (P less than 0.005). There was no significant effect of exercise or subject fitness category on the percentage of T-suppressor lymphocytes, although the absolute numbers of this subset increased significantly after exercise in LF subjects. Marked increases (P less than 0.01) in the percentage of NK cells occurred immediately after exercise at all intensities and durations tested; numerical increases in total NK cells were significant in all fitness groups after the highest intensity work (ride 3; P less than 0.005). Irrespective of whether the changes were expressed as percentage or total numbers, recovery to base line occurred at 30 min after exercise. The results suggest that the exercise effect on blood lymphocyte subset percentages in men is transient and occurs across all fitness levels. Concomitant changes in plasma catecholamine concentrations are only weakly associated with these lymphocyte subset percentage responses to exercise. Furthermore, this study shows that the exercise-induced changes in lymphocyte percentages do not consistently reflect changes in the absolute numbers of cells.     

Posthyperpolarization rebound: Gradualness of intensity and duration effects

Rebound was recorded in the latent pacemaker neuron ofLimnaea stagnalis as an off-response to incoming pulses of constant duration (50 msec) and different strengths (0.17–16.1 nA) or of different duration (10 msec-360 sec) and constant strength (5 nA). To pulses of short duration and weak strength this response consists of a single depolarization wave. With an increase in these parameters the wave gradually grows and is followed by a hyperpolarization wave. At an intensity of 10–12 nA or duration of about 200 msec the rebound response becomes spike-shaped, but the spike is completely formed only at 15.2 nA or 4–5 sec. The last stage of its formation is characterized by "constriction" of the depolarization component. A further increase in pulse intensity of the same duration does not change the rebound response. On the other hand, with a further increase in pulse duration in the corresponding series of experiments fresh spikes were continually added to the first, and depending on the choice of durations, this process could be followed step by step. At a duration of about 190 sec the rebound response reached saturation when it consisted of 8 spikes with a total response duration of about 5 sec. These results are used as the basis for a hypothesis of the possible organization of excitation of the somatic membrane of mollusk pacemaker neurons. Some aspects of the possible mechanism of rebound formation are discussed.Institute of Physiology and Pathology of the Cardiovascular System, Kaunas Medical Institute, Kaunas, Lithuania. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 451–459, September–October, 1973.