Rest-activity rhythms characteristics and seasonal changes in seasonal affective disorder

ABSTRACT

Identifying objectively measurable seasonal changes in 24-h activity patterns (rest-activity rhythms or RARs) that occur in seasonal affective disorder (SAD) could help guide research and practice towards new monitoring tools or prevention targets. We quantified RARs from actigraphy data using non-parametric and extended cosine based approaches, then compared RARs between people with SAD and healthy controls in the summer (n = 70) and winter seasons (n = 84). We also characterized the within-person seasonal RAR changes that occurred in the SAD (n = 19) and control (n = 26) participants who contributed repeated measures. Only controls had significant winter increases in RAR fragmentation (intra-daily variability; in controls mean winter-summer changes (log scale) = 0.05, 0.21 standard deviation, p = 0.03). In SAD participants only, estimated evening settling times (down-mesor) were an average of 30 min earlier in the winter compared with the summer (1-h standard deviation, p = 0.045). These RAR characteristics correlated with greater fatigue (Spearman r = 0.36) but not depression symptom severity. Additional research is needed to ascertain why healthy controls, but not people with SAD, appear to have increased RAR fragmentation in the winter. People with SAD lacked this increase in RAR fragmentation, and instead had earlier evening setting in the winter. Prospective and intervention studies with greater temporal resolution are warranted to ascertain how these seasonal behavioral differences relate to fatigue pathophysiology in SAD. Future research is needed to determine whether extending the winter active period, even in relatively fragmented bouts, could help reduce the fatigue symptoms common in SAD.     

Resource limitation,predation risk and compensatory growth in a damselfly

Periods of poor nutrition during early development may have negative fitness consequences in subsequent periods of ontogeny. In insects, suppression of growth and developmental rate during the larval stage are likely to affect size and timing of maturity, which in turn may lead to reduced reproductive success or survivorship. In light of these costs, individuals may achieve compensatory growth via behavioural or physiological mechanisms following food limitation. In this study, we examined the effects of a temporary period of food restriction on subsequent growth and age and size at maturity in the larval damselfly Ischnura verticalis (Odonata: Coenagrionidae). We also asked whether this temporary period of reduced nutrition affected subsequent foraging behaviour under predation risk. I. verticalis larvae exposed to a temporary food shortage suffered from a reduced growth rate during this period relative to a control group that was fed ad libitum. However, increased growth rates later in development ensured that adult body size measurements (head and pronotum widths) did not differ between the treatments upon emergence. In contrast, adult dry mass did not catch up to that of the controls, indicating that the increased growth rates for size dimensions occur at the cost of similar gains in mass. Predators reduced foraging effort of larvae, but this reduction did not differ between control larvae and those previously exposed to poor nutrition.     

Variations in Red Snapper oocyte development and spawning in relation to environmental and habitat parameters

Environmental Biology of Fishes - The reproductive biology of Red Snapper, Lutjanus campechanus, is well understood, but there is little information on the impact of environmental, climatic, and...     

A comparison of survey and focal follow methods for estimating individual activity budgets of cetaceans

Activity budget data are essential for determining behavioral responses to physiological and ecological variables. Yet, few studies are available to investigate the robustness, accuracy, and biases of the methods used to estimate activity budgets for cetaceans. In this study, we compare activity budgets of 55 adult female bottlenose dolphins in Shark Bay, Australia derived from two methods: surveys (n = 6,903) and focal follows (n = 1,185, totaling 2,721 h of observation). Activity budgets estimated from survey data differed in all behavioral states compared to focal follow data. However, when controlling for temporal autocorrelation, only time spent socializing and time spent traveling remained disparate between the methods. To control for biases associated with assigning group‐level behavior to individuals, we also compared survey and focal follow activity budgets for lone females. Here we found differences between methods in time spent foraging and traveling regardless of whether we controlled for temporal autocorrelation, which suggests detection biases likely play a role in explaining differences in activity budget estimates between the two methodologies. Our results suggest that surveys are less representative of individual‐level activity budgets, and thus, when individual‐level knowledge about behavior is needed, focal follows are preferred.     

Probing adenylation: using a fluorescently labelled ATP probe to directly label and immunoprecipitate VopS substrates

The bacterial effector VopS from Vibrio parahaemolyticus modifies host Rho GTPases to prevent downstream signalling, which leads to cell rounding and eventually apoptosis. While previous studies have used [α-(32)P] ATP for studying this enzyme, we sought to develop a non-radioactive chemical probe of VopS function. To guide these studies, the kinetic parameters were determined for a variety of nucleotides and the results indicated that the C6 position of adenosine was amenable to modification. Since Fl-ATP is a commercially available ATP analogue that is fluorescently tagged at the C6 position, we tested it as a VopS substrate, and the results show that VopS uses Fl-ATP to label Cdc42 in vitro and in MCF7 whole cell extracts. The utility of this probe was further demonstrated by immunoprecipitating Fl-ATP labeled Cdc42 as well as several novel substrate proteins. The proteins, which were identified by LC-MS/MS, include the small GTPases Rac1 and Cdc42 as well as several proteins that are potential VopS substrates and may be important for V. parahaemolyticus pathology. In total, these studies identify Fl-ATP as a valuable chemical probe of protein AMPylation.