Human Core Temperature Responses during Exercise and Subsequent Recovery: An Important Interaction between Diurnal Variation and Measurement Site

Chronobiological investigations into core temperature during and after exercise can involve ambulatory measurements of intestinal temperature during actual competitions, esophageal temperature measurements in laboratory simulations, or rectal temperature, which can be measured in both the field and laboratory. These sites have yet to be compared during both morning and afternoon exercise and subsequent recovery. At 08∶00 and 17∶00 h, seven recreationally active males exercised at 70% peak oxygen uptake for 30 min and then recovered passively for 30 min. During the experiment, esophageal, rectal, intestinal, and skin temperatures, plus sweat loss, heart rate, and ratings of perceived exertion (RPE), were monitored. We found that the diurnal variation in intestinal temperature responses (0.45±0.32°C; mean±SD) was significantly larger compared with rectal (0.33±0.24°C) and, particularly, esophageal temperature responses (0.21±0.20°C; p= 0.019). This reflected a greater difference of 0.25–0.40°C between the esophagus and the other two sites in the afternoon, compared to inter‐site differences of only 0.13–0.16°C in the morning. Diurnal variation was small for skin temperature, heart rate, sweat loss, and RPE responses during exercise (p>0.05). Our data suggest that the relative differences between intestinal, rectal, and esophageal temperature during exercise and subsequent recovery depend on time of day to the extent that inferences from studies on experimental and applied chronobiology will be affected.     

Circadian Variation in Cardiac Autonomic Activity: Reactivity Measurements to Different Types of Stressors

The role of endogenous circadian rhythmicity in autonomic cardiac reactivity to different stressors was investigated. A constant routine protocol was used with repeated exposure to a dual task and a cold pressor test. The 29 subjects were randomly divided into two groups in order to manipulate prior wakefulness. Group 1 started at 09:00 h immediately after a monitored sleep period, whereas group 2 started 12 h later. Measures of interbeat intervals (IBI), respiratory sinus arrythmia (RSA, a measure of parasympathetic activity), pre-ejection period (PEP, a measure of sympathetic activity), as well as core body temperature (CBT) were recorded continuously. Multilevel regression analyses (across-subjects) revealed significant (mainly 24 h) sinusoidal circadian variation in the response to both stressors for IBI and RSA, but not for PEP. Individual 24 + 12 h cosine fits demonstrated a relatively large interindividual variation of the phases of the IBI and RSA rhythms, as compared to that of the CBT rhythm. Sinusoidal by group interactions were found for IBI and PEP, but not for RSA. These findings were interpreted as an indication for endogenous circadian and exogenous parasympathetic (vagal) modulation of cardiac reactivity, while sympathetic reactivity is relatively unaffected by the endogenous circadian drive and mainly influenced by exogenous factors.     

Seasonal Effect on Infants' Sleep Regulation: A Preliminary Study in a Mediterranean Climate

Infants' sleep-wake rhythms are influenced by multiple factors, including developmental and contextual aspects, as well as circadian cycles. Empirical studies that address the seasonal impact on infants' sleep are scarce. The present study examined aspects of sleep schedule and quality, comparing summer and winter months in a Mediterranean climate. This report is based on a convenience sample of 34 healthy 7-mo-olds, an age in which sleep is well consolidated and regulated compared with the first few months of life. Sleep was measured with actigraphy, in the home context. It was found that compared with winter, in the summer months, sleep onset occurred at a later hour, and more motor activity during sleep was detected. Although the overall sleep quality, as defined by sleep efficiency score, was similar in the two seasons, in the summer, more active sleep was observed. The authors discuss the finding in terms of circadian rhythms, developmental characteristics, as well as possible environmental factors and family routines, and call for more studies, in different climates and geographical zones, and in different developmental periods. (Author correspondence: cohen.dini@gmail.com or anats@edu.haifa.ac.il)     

Alterations of the Characteristics of the Circadian Rest‐Activity Rhythm of Cancer In‐Patients

The aim of the present study was to evaluate the characteristics of the circadian rest‐activity rhythm of cancer patients. Thirty‐one in‐patients, consisting of 19 males and 12 females, were randomly selected from the Regional Cancer Center, Pandit Jawaharlal Nehru Medical College, Raipur, India. The rest‐activity rhythm was studied non‐invasively by wrist actigraphy, and compared with 35 age‐matched apparently healthy subjects (22 males and 13 females). All subjects wore an Actiwatch (AW64, Mini Mitter Co. Inc., USA) for at least 4–7 consecutive days. Fifteen‐second epoch length was selected for gathering actigraphy data. In addition, several sleep parameters, such as time in bed, assumed sleep, actual sleep time, actual wake time, sleep efficiency, sleep latency, sleep bouts, wake bouts, and fragmentation index, were also recorded. Data were analyzed using several statistical techniques, such as cosinor rhythmometry, spectral analysis, ANOVA, Duncan's multiple‐range test, and t‐test. Dichotomy index (I<O) and autocorrelation coefficient (r24) were also computed. The results validated a statistically significant circadian rhythm in rest‐activity with a prominent period of 24 h for most cancer patients and control subjects. Results of this study further revealed that cancer patients do experience a drastic alteration in the circadian rest‐activity rhythm parameters. Both the dichotomy index and r24 declined in the group of cancer patients. The occurrence of the peak (acrophase, Ø) of the rest‐activity rhythm was earlier (p<0.001) in cancer patients than age‐ and gender‐matched control subjects. Results of sleep parameters revealed that cancer patients spent longer time in bed, had longer assumed and actual sleep durations, and a greater number of sleep and wake bouts compared to control subjects. Further, nap frequency, total nap duration, average nap, and total nap duration per 1 h awake span were statistically significantly higher in cancer patients than control subjects. In conclusion, the results of the present study document the disruption of the circadian rhythm in rest‐activity of cancer in‐patients, with a dampening of amplitude, lowering of mean level of activity, and phase advancement. These alterations of the circadian rhythm characteristics could be attributed to disease, irrespective of variability due to gender, sites of cancer, and timings of therapies. These results might help in designing patient‐specific chronotherapeutic protocols.     

Regulation of secretory activity in the albumen gland of the pulmonate snail Lymnaea stagnalis (L.)

The secretory activity of the albumen gland of the freshwater snail Lymnaea stagnalis was studied morphometrically (both at the light- and at the electron-microscope level) and biochemically under the following experimental conditions: (1) glandular tissue was implanted into acceptor snails and the glandular activity of the implants was compared to that of the glands of the donors and acceptors; (2) glandular activity was measured at various periods after oviposition; and (3) the activity was measured during a 24 h cycle (diurnal activity). The results indicate that cellular release of secretion material is regulated by a nervous mechanism, whereas synthetic activity is under hormonal control.     

Acid Phosphatase as a Selective Marker for a Class of Small Sensory Ganglion Cells in Several Mammals: Spinal Cord Distribution,Histochemical Properties,and Relation to Fluoride-Resistant Acid Phosphatase (FRAP) of Rodents

Fluoride-resistant acid phosphatase (FRAP) activity as characterized in rat and mouse was studied in sensory ganglion and spinal cord of several mammals, using both the Gomori lead-ion capture and azo-dye coupling methods. FRAP was specifically localized to small- and medium-diameter primary afferent neurons and inner substantia gelatinosa of all nonrodent animals studied, including rabbit, cat, dog, monkey, cow, and human. In rabbit, sciatic nerve transection resulted in depletion of enzymatic activity in ipsilateral spinal cord dorsal horn in a pattern corresponding to the distribution of central terminals of the nerve. Further analysis of the substrate specificity and pH dependence of FRAP was carried out primarily in rat sensory ganglion and spinal cord; the enzyme was found to hydrolyze a wide variety of phosphomonoesters in a relatively nonselective manner at both pH 5 and pH 7, including 5′-nucleotides, phosphorylated amino acids, and several exogenous compounds.

The visualization of FRAP-like activity in several nonrodent species is discussed with reference to previous work indicating its presence only in mouse and rat. Technical factors are considered that limit the applicability of the lead-ion histochemical method in demonstration of FRAP and in efforts at functional characterization of the enzyme, especially in light of its ability to hydrolyze a broad spectrum of substrates over a wide pH range. Alternative interpretations of the expression of acid phosphatase activity in a select class of small sensory ganglion cells are suggested, including several possible nonsynaptic roles of FRAP in the peripheral nervous system.     

Set-Related Activity in the Premotor Cortex of Rhesus Monkeys: Effect of Triggering Cues and Relatively Long Delay Intervals

“Set-related activity” has been defined as a significant alteration in neuronal discharge rate during an “instructed delay period,” a period when a previously instructed movement is being withheld. It has been argued that set-related activity in the primate premotor cortex, or at least a significant proportion of it, reflects motor preparation. In most previous investigations, however, in which visual stimuli have triggered the movement and simultaneously indicated its target, set-related activity might reflect either the anticipation of or attention to the trigger stimulus. The present report shows that set-related activity is robust and can be directionally selective when trigger stimuli do not indicate the target and when a trigger stimulus is absent. Another feature of previous studies has been the relatively brief intervals between the instruction and trigger stimuli (typically 3 sec or less). In the present study, we were able to observe the activity of a small number of cells during longer delay periods. Set-related activity persists, although it becomes less consistent, for as much as 7.5 sec after an instruction stimulus. These results support the hypothesis that set-related activity reflects the preparation for specific limb movements.     

Addressing STEM Concepts through a Food Safety Activity

The activity described in this article engages students in learning about proper meat storage procedures by using the Internet. They apply their knowledge practically through creation of a pamphlet to be displayed in their kitchen at home and a follow-up report on their parents’ kitchen procedures; they may also participate in a classic food storage experiment. This activity is well suited for elementary school children in the second through fourth grades and promotes all basic STEM (science, technology, engineering, and math) concepts. Kitchen activities require all these concepts for successful and safe outcomes. The examination of food storage devices references engineering, and technology is used for the research and pamphlet creation. The section on bacteria introduces life sciences, and physical sciences come into play through the discussion of heat inducing change in the meats. Math skills are integral to the reference table containing temperatures and times.     

Economic activity in the South-Asian population in Britain: the impact of ethnicity,religion, and class

This paper expands the existing literature on ethnicity and economic activity in Britain by studying the impact of religion and class. It argues that while the class location of the different South-Asian groups is important in determining their labour market outcomes, it does not operate independently from ethnicity; rather it is highly influenced by ethnicity in the process of determining the labour market participation of these groups. We use data obtained from the 2001 UK Census on Indian, Pakistani, and Bangladeshi men and women aged between twenty and twenty nine. Our findings confirm that class structure of the South-Asian groups is highly ethnicized, in that the ethno-religious background and class are interwoven to the extent that the separation between them is not easy, if not impossible.