Nocturnal Pattern Research Articles

Diel patterns of foraging aggression and antipredator behaviour in the trashline orb-weaving spider, Cyclosa turbinata

Diel rhythms of physiology and behaviour are present in virtually all taxa examined to date. However, few studies have rigorously assessed the adaptive value of physiological and behavioural rhythms in animals. We laid the groundwork for an assessment of the adaptive rhythm hypothesis by assaying diel rhythms of foraging and antipredator behaviour in the trashline orb-weaver Cyclosa turbinata (Araneae: Araneidae). When confronted with a predator stimulus in experimental arenas, C. turbinata showed thanatosis behaviour more frequently and for longer durations during the day. However, assays of antipredator response within webs revealed more complex diel patterns of avoidance behaviours and no pattern of avoidance behaviour duration. A preliminary assay of prey capture behaviour suggested that C. turbinata also shows nocturnal patterns of foraging aggression. A refined foraging experiment, in which we randomized prey stimulus frequency, found that time of day and spider ID strongly predicted the likelihood of showing prey capture behaviour. Only spider ID predicted latency to attack the prey stimulus despite low individual repeatability (r = 0.10). These results support our prediction that C. turbinata modulate foraging aggression over the diel cycle, but we found no evidence of a trade-off between foraging behaviour and predator vigilance. However, overall patterns of vigilance may be masked by diel changes in antipredator strategies that correspond to fluctuations in the relative abundances of predator types.

Behavioral Masking and cFos Responses to Light in Day- and Night-Active Grass Rats.

Light not only entrains the circadian system but also has acute effects on physiology and behavior, a phenomenon known as masking. Behavioral masking responses to bright light differ in diurnal and nocturnal species, such that light increases arousal in the former and decreases it in the latter. Comparisons made within a species that displays both diurnal and nocturnal patterns of behavior may provide insight into how masking differs between chronotypes and the association between mechanisms controlling masking and the circadian drive for activity. Nile grass rats (Arvicanthis niloticus) provide a useful model for studying such issues because when these animals are housed with running wheels, some run primarily during day, while others run at night. Here we compared behavioral masking responses to 2-h pulses of light and darkness given across a 12:12 light/dark cycle in day-active (DA) and night-active (NA) grass rats. Both wheel-running activity (WRA) and general activity (GA) were monitored. Light pulses at night tended to increase both WRA and GA overall in the DA grass rats, while in NA grass rats, light pulses significantly reduced WRA but had no effect on GA. Dark pulses during the day tended to decrease both WRA and GA in the DA grass rats, while in the NA grass rats, they tended to increase WRA in the early day but had no effect on GA overall. Next, we measured cFos expression within 2 brain areas potentially involved in masking, the intergeniculate leaflet (IGL) and the olivary pretectal area (OPT), of DA and NA grass rats either sacrificed on a control night or after a 1-h light pulse at ZT14. In DA grass rats, light at ZT14 induced cFos in the IGL and OPT, whereas in NA grass rats, cFos levels in both structures were high at ZT14 and were not altered by a 1-h light pulse. Overall, these results suggest that masking responses to light and darkness are dependent on the chronotype of the individual and that the responsiveness of the IGL and OPT to light may depend on or contribute to the behavioral response of these animals.

Effects of different colors of light on melatonin suppression and expression analysis of Aanat1 and melanopsin in the eye of a tropical damselfish

Ocular melatonin production exhibits a daily rhythm with a decrease during photophase and an increase during scotophase (nocturnal pattern) in teleost fish due to day–night changes in the activity of the rate-limiting melatonin synthesizing enzyme arylalkylamine N-acetyltransferase (AANAT). Acute light exposure during scotophase suppresses AANAT activity and melatonin production in the eyes, suggesting that external light signals are a principal regulator of ocular melatonin synthesis. To better understand the photic regulation of ocular melatonin synthesis in teleost fish, this study sought to characterize the effect of light on ocular melatonin synthesis in the sapphire devil Chrysiptera cyanea, which shows a nocturnal pattern and light-induced inhibition of ocular melatonin production during scotophase. Exposure to three different wavelengths of light (half-peak bandwidth=435–475nm with a peak of 455nm, 495–565nm with a peak of 530nm, and 607–647nm with a peak of 627nm for the blue, green, and red LEDs) for 2h during scotophase resulted in the blue wavelength significantly decreasing ocular melatonin content within 30min after light exposure. This result clearly indicates that the effective range of visible light on ocular melatonin suppression is distributed within the wavelengths of blue light and that a blue light-sensitive opsin is involved in ocular melatonin suppression in the fish. A PCR-based cloning method revealed the expression of melanopsin, a putative blue light-sensitive nonvisual opsin, in the eyes. Furthermore, in situ hybridization using the sapphire devil Aanat1 and melanopsin RNA probes showed mRNA expressions of both genes in the inner nuclear and ganglion cell layer of the fish retina. These results suggest that melanopsin is a possible candidate photoreceptor involved in ocular melatonin suppression by an external light signal in the sapphire devil.

Nocturnal patterns of heart rate and the risk of mortality after acute myocardial infarction

The purposes of this study were to identify nocturnal patterns of heart rate (HR) in depressed and nondepressed patients after an acute myocardial infarction (MI) and to determine which patterns, if any, are associated with all-cause mortality or recurrent infarction. Functional data analysis and model-based clustering methods were used to identify nocturnal HR patterns in 245 depressed and 247 nondepressed patients with a recent MI. All-cause mortality and recurrent infarctions were ascertained over a median follow-up of 24 months. Three HR activity patterns were identified. In the first, HR gradually declined during the nighttime and increased the next morning. The second pattern was similar, but with a higher overall HR during the recording interval. The third showed almost no decrease in HR at night (ie, "nondipping"). All-cause mortality was higher among patients with pattern 3 than pattern 1 (P = .007), and the combined end point of recurrent MI or all-cause mortality was higher in pattern 3 than pattern 2 (P = .05). Patterns 2 and 3 were more common in the depressed than in the nondepressed patients. The nondipping nocturnal HR independently predicts all-cause mortality and recurrent MI. Future studies should examine the underlying causes of nondipping nocturnal HR and its association with depression and investigate the effects of treatment on survival.

Relationship between hypertension, obstructive sleep apnea and circadian pattern of urine sodium excretion

wave velocities (PWVs) and impedance cardiography (BioZ) to confirm systemic hemodynamics (cardiac stroke volume/output). Results: Ages were 62 and 25 years respectively, heights 158 and 154 cm, weights 71 and 47 kg, last office BP values 119/73 and 127/80 mmHg. Mean respective 24-hour values were: BP 111/59 and 111/68 mmHg with normal nocturnal dipping patterns, heart rates 69 and 86 beats/min, cardiac outputs 4.6 and 4.3 L/min, central systolic BPs 98 and 103 mmHg, and augmentation indexes 135 and 120% (all well within 95% confidence bands). All regional PWV values were at or below the mean and median for age-adjusted or systolic BP-adjusted values. Conclusions: These findings have potential clinical and scientific implications: chronic amiloride monotherapy maintains normal office and 24-hour BP homeostasis and systemic hemodynamics in GRA, with no evidence of accelerated age-related arterial stiffening. They further suggest that either (a) hyperaldosteronism per se does not cause enhanced vascular fibrosis in humans or (b) amiloride blocks a putative pro-fibrotic effect of Aldo by an unknown mechanism.

Invertebrate drift in the piedmont part of the Kedrovaya River (Primorsky Krai, Russia) in warm season

Diurnal dynamics of invertebrate drift in the Kedrovaya River (Primorsky Krai, Russia), which flows in the zone of influence of the monsoon climate, has been studied. It has been shown that drifting invertebrates tend to shift from a predominantly daytime drift pattern to a distinguished nocturnal drift pattern during the frost-free period. The ratio of the total number of nighttime migrants to the total number of daytime migrants increased with every subsequent month. It has been proposed that the degree of light contrast between day and night can be significant in the regulation of nocturnal drift intensity.

Occurrence of invasive mammals in southern Nahuel Huapi National Park

Introduced mammals in Patagonia are believed to negatively influence native ecosystems. We surveyed invasive mammals using camera traps in Nahuel Huapi National Park, Argentina, from February to May 2012. We deployed 19 cameras for about 30 days each, for a total of 645 camera days. We obtained 352 independent detections of three invasive mammal species: 67% European hare (Lepus europaeus), 32% wild boar (Sus scrofa), and 1% red deer (Cervus elaphus); no native herbivorous or omnivorous mammals were detected. All species showed nocturnal activity patterns. Hare detections reflected generalist habitat use and wild boars showed preference for more humid areas. The increased detection near roads suggests hares and wild boars are being facilitated through human disturbance, which should be considered in management decisions.

Habitat selection by large herbivores in a southern African savanna: the relative roles of bottom‐up and top‐down forces

Animals must often balance food availability and predation risk when selecting habitat. Here, we examined habitat preferences of large mammalian herbivores in a long‐term fire experiment in the Kruger National Park, South Africa to assess the role of bottom‐up (e.g., forage quantity/quality) and top‐down (e.g., predation risk) processes in driving herbivore distributions. We focused on experimental plots (∼10 ha on average) that have been burned in the winter (August) since 1954 at 1‐ and 3‐yr intervals, or left unburned (n = 3 per burn type). Herbivore distributions (during both day and night) and plant community structure were surveyed on each plot during the growing seasons (November–March) of 2005–2006, 2006–2007, and 2007–2008. Overall, we sighted 4,187 individuals representing twelve species of mammalian herbivores. Impala (Aepyceros melampus), zebra (Equus quagga), and wildebeest (Connochaetes taurinus) comprised 37%, 28%, and 18% of all individuals observed, respectively. Several species such as African buffalo (Syncerus caffer), wildebeest, and giraffe (Giraffa camelopardalis) exhibited a significant trade‐off between food acquisition and minimizing predation risk by foraging in areas with lower density of woody vegetation. We also observed significant day vs. night dynamics in herbivore habitat selection. For example, zebra utilized annual or triennial burns during the day depending on which years the plots were burned, but they avoided triennial burns with dense woody vegetation in favor of more open annual burns at night when predators such as lions (Panthera leo) are more active. Similarly, the smaller, mixed‐feeding impala appeared to use riskier habitats with more diverse forage options during the day (triennial burns and unburned plots) but used less risky habitats at night (annual and triennial burns). Diurnal vs. nocturnal patterns are often overlooked in studies of habitat selection but are necessary for understanding the factors that shape distribution. The variation we observed in herbivore distribution patterns during this three‐year period indicates that different species exhibit different trade‐offs with respect to food and predation risk. Factors such as body size, nutritional requirements, prey escape tactics, and recent fire history likely mediated these interspecific differences.

A Long-Term Assessment of the Variability in Winter Use of Dense Conifer Cover by Female White-Tailed Deer

BackgoundLong-term studies allow capture of a wide breadth of environmental variability and a broader context within which to maximize our understanding of relationships to specific aspects of wildlife behavior. The goal of our study was to improve our understanding of the biological value of dense conifer cover to deer on winter range relative to snow depth and ambient temperature.Methodology/Principal FindingsWe examined variation among deer in their use of dense conifer cover during a 12-year study period as potentially influenced by winter severity and cover availability. Female deer were fitted with a mixture of very high frequency (VHF, n = 267) and Global Positioning System (GPS, n = 24) collars for monitoring use of specific cover types at the population and individual levels, respectively. We developed habitat composites for four study sites. We fit multinomial response models to VHF (daytime) data to describe population-level use patterns as a function of snow depth, ambient temperature, and cover availability. To develop alternative hypotheses regarding expected spatio-temporal patterns in the use of dense conifer cover, we considered two sets of competing sub-hypotheses. The first set addressed whether or not dense conifer cover was limiting on the four study sites. The second set considered four alternative sub-hypotheses regarding the potential influence of snow depth and ambient temperature on space use patterns. Deer use of dense conifer cover increased the most with increasing snow depth and most abruptly on the two sites where it was most available, suggestive of an energy conservation strategy. Deer use of dense cover decreased the most with decreasing temperatures on the sites where it was most available. At all four sites deer made greater daytime use (55 to >80% probability of use) of open vegetation types at the lowest daily minimum temperatures indicating the importance of thermal benefits afforded from increased exposure to solar radiation. Date-time plots of GPS data (24 hr) allowed us to explore individual diurnal and seasonal patterns of habitat use relative to changes in snow depth. There was significant among-animal variability in their propensity to be found in three density classes of conifer cover and other open types, but little difference between diurnal and nocturnal patterns of habitat use.Conclusions/SignificanceConsistent with our findings reported elsewhere that snow depth has a greater impact on deer survival than ambient temperature, herein our population-level results highlight the importance of dense conifer cover as snow shelter rather than thermal cover. Collectively, our findings suggest that maximizing availability of dense conifer cover in an energetically beneficial arrangement with quality feeding sites should be a prominent component of habitat management for deer.

Effect of amphetamine on the clock gene expression in rat striatum

Drug addicts have severe disruptions in many physiological and behavioral rhythms, such as the sleep/wake cycle. Interestingly, amphetamine, a psychostimulant, is able to alter many circadian patterns, which are independent of the master biological clock located in the suprachiasmatic nucleus. To increase our understanding of the circadian regulation of amphetamine on clock gene expression, rats received subcutaneous injections of d-amphetamine and the clock gene mRNA levels were analyzed using real-time PCR to obtain a daily profile. In the striatum, acute injection of d-amphetamine did not alter Period (Per)1, Per2 and Reverse erythroblastosis virus α (Rev-erbα) expressions. Chronic administration shifted the phase of Per1 and Per2 expressions from a nocturnal to diurnal pattern and advance shifted the peak of Rev-erbα in d-amphetamine-treated animals. In contrast, the rhythm of Brain and muscle Arnt-like protein-1 (Bmal1) was shifted from a diurnal to a nocturnal pattern by both acute and chronic treatments. These results demonstrated that chronic d-amphetamine treatment altered the expression of clock genes in the striatum. This might further influence the expression of related gene within the striatum and lead to behavioral and physiological changes which are associated to drug addiction.

Abstract TP209: Time Of Stroke Onset Is Not Associated With Risk Of Obstructive Sleep Apnea In Intracerebral Hemorrhage.

Objective: To test the hypothesis that risk status for obstructive sleep apnea (OSA) is associated with time of onset in intracerebral hemorrhage. Background: OSA can affect 30-70% of patients with ischemic strokes, intracerebral hemorrhage and transient ischemic attacks. In normal sleep, blood pressure and heart rate decrease due to increased parasympathetic activity. In OSA, increased sympathetic activity during sleep can lead to a absence of this blood pressure fall. This non-dipping nocturnal blood pressure pattern has been associated with a shift in the timing of sudden cardiac death, from 7am-noon in those without OSA to 12am-6am in those with OSA. Whether this diurnal shift exists in intracerebral hemorrhage cases at high risk for OSA has not been studied. Method: A nested case control study within the interviewed case cohort from the Ethnic/Racial Variations of Intracerebral Hemorrhage (ERICH) study was performed. OSA risk status was categorized as “high-risk” based on a positive score in 2 out of 3 categories on the Berlin questionnaire, which ascertains snoring, daytime fatigue, body mass index and hypertension. Timing of intracerebral hemorrhage was categorized as “Nocturnal” based on a known time of stroke onset from 22:00pm to 06:00am and “Awake” based on a known time of stroke onset from 06:01am to 21:59pm. Results: Time of stroke onset was known in 434 subjects. The Berlin questionnaire categorized 54.2% of cases as high-risk for OSA. In comparison with low-risk subjects, high-risk cases tended to be younger (59.1±13.7 vs. 61.8±15.7, p=0.05), male (48% vs 58%, p=0.03), have coronary disease (6% vs 11%, p=0.09), have diabetes (27% vs 18%, p=0.02), and have dyslipidemia (43% vs 30%, p=0.006). There were no ethnic differences in the prevalence of high risk for OSA (P=0.60). Nocturnal strokes were seen in 17% of high- and low-risk OSA cases. There was no statistically significant difference in OSA status and timing of stroke (p=0.98). Conclusions: OSA risk status was not associated with timing of hemorrhagic stroke. This finding suggests that a non-dipping nocturnal blood pressure pattern is not seen in intracerebral hemorrhage cases at high-risk for OSA.

Reduced drift activity of two benthic invertebrate species is mediated by infochemicals of benthic fish

Regulating mobility by actively entering the drift under imminent predation risk is an avoidance strategy employed by aquatic macroinvertebrate species that is widely accepted within the scientific community. This response was most evident with respect to diurnal predators that feed in the water column, such as many salmonids. We investigated the role of the nocturnal benthivorous gudgeon [Gobio gobio (L.)] on the drift activity of two macroinvertebrate species known to display this behaviour: Baetis rhodani (PICTET) and Gammarus pulex (L.). Laboratory drift experiments using gudgeon kairomones were conducted with the results determining significant altered activity in the presence of gudgeon kairomones for both macroinvertebrate species. B. rhodani showed reduced drift activity in the kairomone treatment compared to the kairomone-free control, with a distinct nocturnal pattern being observed for both. G. pulex shifted from a similar day/night movement pattern to a nocturnal movement pattern with decreased activity during the day. Reduce activity during the day, whilst maintaining normal activity at night would not reduce the probability of encountering a nocturnal predator under natural conditions and therefore appears to not be a meaningful anti-predator response. To assess the relevance of these findings under natural conditions, we compared the experimental results with drift measurements from field observations. These show a significant reduction in drift activity for G. pulex and slight tendencies for reduced night-time drift for B. rhodani, under seasonal variations. We conclude that the behaviour in response to the physical contact or the hydrodynamic stimuli of nocturnal predators is the most likely explanation for the differences between the results from our laboratory experiment and the field observation. We further discuss that the observed migration patterns might have different species specific consequences for density stabilisation on a population level.

Daily activity patterns of brown bear (Ursus arctos) of the Sikhote-Alin mountain range (Primorskiy Krai, Russia)

Daily activity patterns of brown bears were monitored using radiotelemetry from 1993 to 2006, in the Sikhote-Alin Biosphere Reserve and adjacent areas. Outside of the denning period, bears were active for approximately 52% of the 24-hour period. Males were more active (64% of total time) than females (51%). Brown bears in the Sikhote-Alin are diurnal and crepuscular, but switch to a nocturnal pattern in areas of high anthropogenic influence. During the summer months, daily activity patterns were influenced by precipitation, cloud cover, and air temperature.

Same Temporal Niche, Opposite Rhythmicity: Two Closely Related Bioluminescent Insects With Opposite Bioluminesce Propensity Rhythms

Arachnocampa species, commonly called glowworms, are flies whose larvae use light to attract prey. Here we compare rhythmicity in two of the nine described species: the Tasmanian species, Arachnocampa tasmaniensis, which inhabits caves and wet forest, and the eastern Australian mainland species, A. flava, primarily found in subtropical rainforest. Both species show the same nocturnal glowing pattern in external (epigean) environments and the same inhibition of bioluminescence by light and both species show circadian regulation of bioluminescence. We find that the underlying circadian bioluminescence propensity rhythm (BPR) of the two species peaks at opposite phases of the day:night cycle. Larvae of A. flava, placed in constant darkness in the laboratory, bioluminesce during the subjective scotophase, typical of nocturnal animals, whereas A. tasmaniensis shows the opposite tendency, bioluminescing most intensely during the subjective photophase. In A. tasmaniensis, which are exposed to natural day:night cycles, light exposure during the day overrides the high bioluminescence propensity through negative masking and leads to a release of bioluminescence after dusk when the BPR is on the wane. A consequence is that A. tasmaniensis is able to start glowing at any phase of the light:dark cycle as soon as masking by light is released, whereas A. flava is locked into nocturnal bioluminescence. We suggest that the paradoxical BPR of A. tasmaniensis is an adaptation for living in the cave environment. Observations of bioluminescence in colonies of A. tasmaniensis located in the transition from a cave mouth to the dark zone show that glowing is inhibited by light exposure but a peak bioluminescence follows immediately after “dusk” at their location. The substantial difference in the circadian regulation of bioluminescence between the two species probably reflects adaptation to the cave (hypogean) habitat in A. tasmaniensis and the forest (epigean) habitat in A. flava. (Author correspondence: d.merritt@uq.edu.au)

Circadian variability and nocturnal dipping pattern in blood pressure in young normotensive subjects

Blood pressure variability (BPV) is one of the recognized risk factors for different types of cardiovascular diseases (CVDs). Several physiological, behavioral and ethnic factors are known to modulate blood pressure (BP). Such studies on the population of southeast India are altogether absent. It is worthwhile, therefore, to examine the circadian variability in systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) and nocturnal dipping pattern in BP in apparently healthy human subjects as a function of gender. Sixty females and 40 males voluntarily participated in the study. All subjects wore an Ambulatory Blood Pressure Monitor (ABPM, TM 2430) for two to four consecutive days. SBP, DBP and HR was measured every 15 and 30 minutes between 07:00–22:00 and 22:00–07:00 hrs, respectively. In addition, double product (DP) and mean arterial pressure (MAP) were also computed. Data were analyzed using A&D, Cosinor and Spectre software. Prevalence of extreme dipper, dipper and non-dipper was 13%, 63% and 24%, respectively. A statistically significant circadian rhythm was validated in all studied variables, irrespective of gender and dipping pattern in BP. However, the rhythm detection ratio was low among non-dippers. Chi-square test revealed a statistically significant association of the frequency of prominent periods of SBP and MAP with nocturnal dipping categories. Further, significant differences for the circadian Mesors of SBP, DBP, HR, DP and MAP and acrophase of DBP and MAP were noticed between males and females. Dipping pattern produced a significant effect on the rhythm characteristics of all the studied variables. On the basis of our findings we can conclude that variability in BP may be associated with factor gender to some extent, whereas nocturnal dipping in BP is independent of gender. Interestingly in the present study about 24% subjects are non-dippers, which may be an indication of higher risk of CVDs among individuals belonging to younger generation of this region. However, further extensive study is desirable to strengthen the above conjecture.

Temporal organization of activity in the brown bear (Ursus arctos): roles of circadian rhythms, light, and food entrainment

Seasonal cycles of reproduction, migration, and hibernation are often synchronized to changes in daylength (photoperiod). Ecological and evolutionary pressures have resulted in physiological specializations enabling animals to occupy a particular temporal niche within the diel cycle leading to characteristic activity patterns. In this study, we characterized the annual locomotor activity of captive brown bears (Ursus arctos). Locomotor activity was observed in 18 bears of varying ages and sexes during the active (Mar-Oct) and hibernating (Nov-Feb) seasons. All bears exhibited either crepuscular or diurnal activity patterns. Estimates of activity duration (α) and synchronization to the daily light:dark cycle (phase angles) indirectly measured photoresponsiveness. α increased as daylength increased but diverged near the autumnal equinox. Phase angles varied widely between active and hibernating seasons and exhibited a clear annual rhythm. To directly test the role of photoperiod, bears were exposed to controlled photoperiod alterations. Bears failed to alter their daily activity patterns (entrain) to experimental photoperiods during the active season. In contrast, photic entrainment was evident during hibernation when the daily photocycle was shifted and when bears were exposed to a skeleton (11:1:11:1) photoperiod. To test whether entrainment to nonphotic cues superseded photic entrainment during the active season, bears were exposed to a reversed feeding regimen (dark-fed) under a natural photocycle. Activity shifted entirely to a nocturnal pattern. Thus daily activity in brown bears is highly modifiable by photoperiod and food availability in a stereotypic seasonal fashion.

Abstract 288: Nocturnal Blood Pressure Elevation or Abnormal Circadian Pattern. Which is Better Associated with Cardiovascular Risk?

Background and aim: A blunted decrease in nighttime BP with respect to daytime values (the non-dipping pattern) and an absolute increase in nocturnal BP have both been related to a worse cardiovascular prognosis. However, these are not independent variables and little is know about which is better related with cardiovascular risk. The aim of the study was to compare clinical data in untreated hypertensives classified on the basis of both absolute nocturnal BP and the dipping pattern. Methods: We included 37096 untreated patients from the Spanish ABPM Registry. They were classified in 4 different groups: Group 1: 15743 (42%) with mean nocturnal systolic BP (NSBP) < 120 mmHg and nocturnal systolic dip (NSD) ≥ 10%; Group 2: 6166 (17%) patients with NSBP < 120 mmHg and NSD < 10%; Group 3: 4847 (13%) patients with NSBP ≥ 120 mmHg and NSD ≥ 10%; and Group 4: 10340 (28%) patients with NSBP ≥ 120 mmHg and NSD < 10%. Groups were compared by ANOVA, Kruskal-Wallis or Chi square statistics (p for trend), with specific comparisons between groups 2 and 3 (Bonferroni corrected t-test, Mann Whitney or Chi square statistics). Results: Compared to patients with elevated NSBP but normal NSD, those with abnormal NSD but normal NSBP were more frequently women, diabetics, had reduced eGFR and had more frequently previous history of cardiovascular complications. The worse cardiovascular risk profile was seen in those patients with both elevated NSBP and abnormal NSD (table). Conclusion: In untreated hypertensive patients an abnormal dipping pattern is more closely related with diabetes and overt cardiovascular and renal disease than nocturnal BP elevation without circadian pattern alterations .

Labile Hypertension: Characteristics of a Referred Cohort

From 88 subjects with labile high blood pressure (LHBP), we collected blood pressure variability (BPV) and assessed relationships with age, medications, and nocturnal pattern via ambulatory blood pressure monitoring. The average age of the subjects was 64 ± 13 years and they were on 1.5 ± 1.3 antihypertensives. BPV did not differ diurnally and was not influenced by medication. Aging associates with increasing daytime systolic but not diastolic BPV, with increasing nighttime systolic BP, and decreasing diastolic BP diurnally. Subjects had widened pulse pressure and abnormal diurnal pattern with age. Further studies are needed to stratify an individual's risk associated with LHBP.

Diel movements of out-migrating Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss) smolts in the Sacramento/San Joaquin watershed

We used ultrasonic telemetry to describe the movement patterns of late-fall run Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (O. mykiss) smolts during their entire emigration down California’s Sacramento River, through the San Francisco Bay Estuary and into the Pacific Ocean. Yearling hatchery smolts were tagged via intracoelomic surgical implantation with coded ultrasonic tags. They were then released at four upriver locations in the Sacramento River during the winters of 2007 through 2010. Late-fall run Chinook salmon smolts exhibited a nocturnal pattern of migration after release in the upper river. This is likely because individuals remain within a confined area during the day, while they become active at night and migrate downstream. The ratio between night and day detections of Chinook salmon smolts decreased with distance traveled downriver. There was a significant preference for nocturnal migration in every reach of the river except the Estuary. In contrast, steelhead smolts, which reside upriver longer following release, exhibited a less pronounced diel pattern during their entire migration. In the middle river, Delta, and Estuary, steelhead exhibited a significant preference for daytime travel. In the ocean Chinook salmon preferred to travel at night, yet steelhead were detected on the monitors equally during the night and day. These data show that closely related Oncorhynchus species, with the same ontogenetic pattern of out-migrating as yearlings, vary in migration tactic.

Nocturnal Peak in Atrial Tachyarrhythmia Occurrence as a Function of Arrhythmia Burden

We examined circadian periodicity of atrial tachyarrhythmias (AT/AF) in a large group of patients with implantable devices, which allow continuous collection of the event data over prolonged periods of time. A total of 16,130 AT/AF events were recorded in 236 patients (age: 63 ± 12 years, 27% female, 90% had a history of cardiovascular disease, 33% ischemic, LVEF: 49 ± 18%) over a period of 12 months. To exclude interactions with therapy, the patterns of arrhythmia occurrence were examined for all events and for those episodes that were preceded by at least 1, 6, and 24 hours of sinus rhythm. To prevent biasing toward patients with more frequent episodes, the patterns of AT/AF onset were analyzed both in absolute and patient-normalized (i.e., divided by the total number of events in each patient) units per hour per patient and then summarized for the entire group. In patients with <4 AT/AF events, the onset times were randomly distributed over 24-hour period. However, as the number of AT/AF events increased, a nocturnal pattern of occurrence (determined by the occurrence of a trough around noon) gradually emerged and became highly statistically significant (P < 10(-4) ). The magnitude of nocturnal peak of AT/AF events was well explained by a single-exponential function (R(2) = 0.97, P < 10(-2) ). Patients with more frequent atrial tachyarrhythmias are more likely to develop AT/AF at night. Knowledge of patient-specific circadian patterns of arrhythmia occurrence can be useful for personalized management of individuals with significant arrhythmia burden.