Ensuing Activity Research Articles

Jura-Cretaceous synorogenic magmatism and relations to supercontinental rifting in the northwestern U.S. Cordillera

Changes in lithospheric composition and strength associated with rifting of the Rodinian supercontinent (ca. 780−485 Ma) served to localize Mesozoic tectonic activity in the McCall region of west-central Idaho, USA. Although discrimination diagrams support slab failure melting, ca. 150−121 Ma calcic magmatism in the Hazard Creek complex and chemically similar intrusive rocks of northeastern Oregon, USA (e.g., Cornucopia stock), is best explained by progressive loading of oceanic crust. Westward-directed thrusting across the Laurentian continental margin and adjacent island-arc terranes (Olds Ferry/Wallowa; Blue Mountains province) led to partial melting of metabasaltic source rocks at pressures and depths sufficient for garnet stability (>10 kbar, ∼35 km). Early pluton emplacement during right-oblique arc−continent collision overlapped in time with subduction zone reorganization, which involved a change in dip direction (westward to eastward) under the accreting Blue Mountains block. Ensuing magmatic activity predated and was concurrent with ca. 116 Ma thrust reactivation of the Wallowa/Olds Ferry boundary, which temporally overlapped with contractional deformation along the terrane−continent accretionary boundary. Later synorogenic magmatism was focused along the accretionary boundary, where rising anatectic melts were caught between the eastward-impinging/northward-migrating (obliquely colliding) terrane block and continental margin backstop (Rodinian rift architecture). Middle Cretaceous dextral transpression viewed in this manner precludes the need for an outboard “hit-and-run” collider (Insular superterrane) and thus, a post-accretion shear zone in western Idaho.

Merging the Analogue and the Digital: Combining Opposite Activities in a Mixed Media Game

While much of the games research field for the last two decades has focused on digital games, this article draws attention to the benefits of combining analogue and digital game components to cater for a serious but fun game experience. In this case, the game design provides a set of game rules for players, where the goal is to win by finding another player’s hidden treasure. But, the game also includes deceptive characters, initially unknown to the players, whose goal is to lure the players to reveal information, which will make a player lose the game. Hence, the players and the unknown characters are involved in opposite but intertwined activities. To describe the differing activities we use the activity system model found in Activity Theory. The theoretical conceptualisation, the game design and the play situation create what we term a <em>zone of experience</em> where young players can experience the consequences of sharing too much information. The game design mimics real world online interactions, but under safe off-line conditions. The zone of experience also creates the foundation for an ensuing activity that fits well within the concept of the zone of proximal development: A follow-up conversation under adult guidance of game experiences aimed at raising children’s online risk awareness.

A Three-Phase Study on Preflush Stage in Sandstone Acidizing: Experimental and Modeling Analysis of Evolved Carbon Dioxide in a Hydrocarbon and Aqueous Environment

SummaryLimited studies have been conducted in understanding the mechanics of preflush stages in sandstone-acidizing processes. Among those conducted in this area, all efforts have been directed toward singular aqueous-phase scenarios. Encountering 100% water saturation (Sw) in the near-wellbore region is seldom the case because hydrocarbons at residual or higher saturations can exist. Carbonate-mineral dissolution, being the primary objective of the preflush stage, results in carbon dioxide (CO2) evolution. This can lead to a multiphase presence depending on the conditions in the porous medium, and this factor has been unaccounted for in previous studies under the assumption that all the evolved CO2 is dissolved in the surrounding solutions. The performance of a preflush stage changes in the presence of multiphase environments in the porous media.A detailed study is presented on the effects of evolved CO2 caused by carbonate-mineral dissolution, and its ensuing activity during the preflush stages in matrix acidizing of sandstone reservoirs. Four Carbon Tan Sandstone cores were used toward the purpose of this study, of which two were fully water saturated and the remaining two were brought to initial water saturation (Swi) and residual oil saturation to waterfloods (Sorw) before conducting preflush-stage experiments. The preflush-stage fluid, 15 wt% hydrochloric acid (HCl), was injected in the concerning cores while maintaining initial pore pressures of 1,200 psi and constant temperatures of 150°F.A three-phase-flow numerical-simulation model coupled with chemical-reaction and structure-property modeling features is used to validate the conducted preflush-stage coreflood experiments. Initially, the cores are scanned using computed tomography (CT) to accurately characterize the initial porosity distributions across the cores. The carbonate minerals present in the cores, namely calcite and dolomite, are quantified experimentally using X-ray diffraction (XRD). These measured porosity distributions and mineral concentrations are populated across the core-representative models. The coreflood effluents' calcium chloride and magnesium chloride, which are acid/carbonate-mineral-reaction products, as well as spent-HCl concentrations were measured. The pressure drop across the cores was logged during the tests. These parameters from all the conducted coreflood tests were used for history matching using the numerical model. The calibrated numerical model was then used to understand the physics involved in this complex subsurface process.In fully water-saturated cores, a major fraction of unreacted carbonate minerals still existed even after 40 pore volumes (PV) of preflush acid injection. Heterogeneity is induced as carbonate-mineral dissolution progresses within the core, creating paths of least resistance, leading to the preferential flow of the incoming fresh acid. This leads to regions of carbonate minerals being untouched during the preflush stimulation stage. A power-law trend, P = aQb, is observed between the stabilized pressure drops at each sequential acid-injection rate vs. the injection rates, where P is the pressure drop across the core, Q is the sequential flow rate, and a and b are constants, with b < 1. An ideal maximum injection rate can be deduced to optimize the preflush stage toward efficient carbonate-mineral dissolution in the damaged zone. An average of 25% recovery of the oil in place (OIP) was seen from preflush experiments conducted on cores with Sorw. In cores with Swi, the oil saturation was reduced during the preflush stage to a similar value as in the cores with Sorw. The oil-phase-viscosity reduction caused by CO2 dissolution in oil and the increase in saturation and permeability to the oil phase resulting from oil swelling by CO2 are inferred as the main mechanisms for any additional oil production beyond residual conditions during the preflush stage. The potential of evolved CO2, a byproduct of the sandstone-acidizing preflush stage, toward its contribution in swelling the surrounding oil, lowering its viscosity, and thus mobilizing the trapped oil has been depicted in this study.

Experimental observations of a rupture induced underwater sound source.

A rupture induced underwater sound source (RIUSS) is being developed as an alternative to other impulsive sound sources commonly utilized in underwater acoustics experiments and surveys. The device is comprised of a graphite rupture disk mounted over an evacuated chamber. After the disk breaks, an inrush of water creates a high amplitude acoustic pulse. A field test was conducted to measure the acoustic output as a function of depth for a given source configuration, and high speed underwater video was simultaneously captured with an acoustic recording system to correlate the features of the acoustic output to the ensuing bubble activity.

Man's Pursuit of Meaning: Unexpected Termination Bolsters One's Autonomous Motivation in an Irrelevant Ensuing Activity.

Meaningfulness has been suggested as one of the fundamental psychological needs, as one would actively pursue meaning in both his/her work life and personal life. Previous studies consistently showed that a lack of meaning in work would reduce one’s autonomous motivation in the current job, which is the motivation to engage in self-determined activities driven by one’s own interests or personal beliefs. However, researchers overlooked the fact that in work settings, it is not uncommon that people work on multiple tasks in a row. As a result, the cross-task effect of work meaningfulness remains understudied. Based on the meaning maintenance model (MMM) and the suggested fluid compensation strategy, we predicted that the disappearance of the meaning of work may induce a compensatory response and thus enhance one’s autonomous motivation in an irrelevant ensuing activity. To test this hypothesis, we invited participants to work on an encyclopedic knowledge quiz in Session 1 and a StopWatch (SW) task in Session 2. A between-subject design was adopted. While participants in the control group successfully completed their tasks in Session 1, those in the experimental group encountered unexpected program quits by the end of the quiz, and their previous efforts suddenly became futile and meaningless. Electroencephalography was recorded during the experiment to measure reward positivity (RewP). In Session 2, a more pronounced RewP in the win–lose difference wave was observed in the experimental group in contrast to the control group, suggesting that the disappearance of the meaning of work enhanced one’s autonomous motivation in an irrelevant activity that follows. Therefore, results of this study provided preliminary electrophysiological evidence for one’s pursuit of meaning and the compensation effect induced by the disappearance of the meaning of work.

Coding, designing and networking: fostering learning through social connections

Trends in digital technologies and new social practices are calling for innovative models of learning in education. A recent development in the learning sciences, which conceptualises learning activity as networked learning, can offer deeper insight into how digital learning spaces influence the ensuing activity of learners. The networked approach coupled with social semiotics is applied in the analysis of Peep – a computer-based platform with social networking features that supports an undergraduate design course. This article illustrates how the networked learning approach and social semiotics reveal elements of the platform that enable design learning and foster social connections amongst students and lecturers. The article also examines the distribution of students’ activity and changes in their patterns of interaction over time. Published : 3 April 2018 Citation : Research in Learning Technology 2018, 26 : 2006 - http://dx.doi.org/10.25304/rlt.v26.2006

26. Rhythmic activity of leg muscles during standing in healthy subjects

Traditionally, the stretch and possibly polysynaptic reflexes are considered the mainstay of antigravity leg muscles. We found evidence of a different mechanism. In a group of young normal subjects, surface EMG was recorded from tibialis anterior, soleus, vastus medialis and biceps femoris muscles in quiet upright stance without and with balance perturbation. In quiet stance, a modest amount of activity could be recorded from the soleus and the biceps femoris only, and none from tibialis anterior and vastus medialis. Such activity was organized in bursts whose duration ranged 50–100 ms, and frequency of 8–12/s. Simultaneous recording of the centre of pressure via stabilometric platform, showed that when a forward shift occurred, frequency and amplitude of the soleus bursts increased, but all activity ceased in a backward shift. When balance was perturbed by a backward tilt, the very first ensuing activity was a brief response by the soleus (weak stretch reflex) followed by several bursts of the tibialis anterior. Little if any activity was recorded from the thigh muscles. We conclude that action of antigravity muscles of the leg seemed more linked to modulation of a rhythmic preordinated activity rather than to a simple reflex response.

Online social contagion modeling through the dynamics of Integrate-and-Fire neurons

We introduce a novel model capturing the dynamics of the online social contagion. We adopt a neuroscience perspective and consider the online social networks analogous to networks of Integrate-and-Fire neurons. The dynamics of the model is driven by three sources of positive or negative influence: The individuals’ self-generated bias, the interpersonal online interactions, and the external environment stimulus. The model explains the online activity growth and the activity propagation patterns in relation to the interaction network, the endogenous and exogenous influence, and the individuals’ activation mechanism. Through simulation experiments and validation against empirical data from Twitter, we demonstrate that the model captures the relationship between the dynamically changing internal and external influence and the ensuing online activity. As such, it can accurately reproduce collective activity patterns arising from the online users’ response to various kinds of stimuli. The model can be generalized to handle a wide class of contagion phenomena.

Identifying recycled ash in basaltic eruptions.

Deposits of mid-intensity basaltic explosive eruptions are characterized by the coexistence of different types of juvenile clasts, which show a large variability of external properties and texture, reflecting alternatively the effects of primary processes related to magma storage or ascent, or of syn-eruptive modifications occurred during or immediately after their ejection. If fragments fall back within the crater area before being re-ejected during the ensuing activity, they are subject to thermally- and chemically-induced alterations. These ‘recycled' clasts can be considered as cognate lithic for the eruption/explosion they derive. Their exact identification has consequences for a correct interpretation of eruption dynamics, with important implications for hazard assessment. On ash erupted during selected basaltic eruptions (at Stromboli, Etna, Vesuvius, Gaua-Vanuatu), we have identified a set of characteristics that can be associated with the occurrence of intra-crater recycling processes, based also on the comparison with results of reheating experiments performed on primary juvenile material, at variable temperature and under different redox conditions.

Intervention Breakdowns as Occasions for Articulating Mobile Health Information Infrastructures

AbstractThis study investigates a mobile health project launched in Malawi and considers its sustainability in light of activities that occur in the pilot stage. It has been said that most projects of this nature fail during piloting hence it is pertinent to review the activities in this early stage. The study follows a grounded theory inspired research approach and is focused on the day to day breakdowns that occur in the pilot, what they reveal, and how the resolutions relate to the project's goals. It is found that when breakdowns occur, an articulation process to sustain the intervention becomes visible. Breakdowns can reveal tensions in the technical design and organisational context thereby offering opportunities for action in order that an intervention is sustained. The ensuing activity, for analytical purposes, is termed articulation work, and its variety and limitations are explained. In this study we discover two categories of articulation work, technological and human. Further to this, we argue that these two categories of articulation work can be further analysed into different dimensions, based on the levels of organizational involvement required to resolve them: (i) localised; (ii) multiple levels within a single organization; (iii) and multiple levels inter‐organizational.

Glyceraldehyde-3-phosphate dehydrogenase is largely unresponsive to low regulatory levels of hydrogen peroxide in Saccharomyces cerevisiae

BackgroundThe reversible oxidation of protein SH groups has been considered to be the basis of redox regulation by which changes in hydrogen peroxide (H2O2) concentrations may control protein function. Several proteins become S-glutathionylated following exposure to H2O2 in a variety of cellular systems. In yeast, when using a high initial H2O2 dose, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was identified as the major target of S-glutathionylation which leads to reversible inactivation of the enzyme. GAPDH inactivation by H2O2 functions to reroute carbohydrate flux to produce NADPH. Here we report the effect of low regulatory H2O2 doses on GAPDH activity and expression in Saccharomyces cerevisiae.ResultsA calibrated and controlled method of H2O2 delivery - the steady-state titration - in which cells are exposed to constant, low, and known H2O2 concentrations, was used in this study. This technique, contrary to the common bolus addition, allows determining which H2O2 concentrations trigger specific biological responses. This work shows that both in exponential- and stationary-phase cells, low regulatory H2O2 concentrations induce a large upregulation of catalase, a fingerprint of the cellular oxidative stress response, but GAPDH oxidation and the ensuing activity decrease are only observed at death-inducing high H2O2 doses. GAPDH activity is constant upon incubation with sub-lethal H2O2 doses, but in stationary-phase cells there is a differential response in the expression of the three GAPDH isoenzymes: Tdh1p is strongly upregulated while Tdh2p/Tdh3p are slightly downregulated.ConclusionsIn yeast GAPDH activity is largely unresponsive to low to moderate H2O2 doses. This points to a scenario where (a) cellular redoxins efficiently cope with levels of GAPDH oxidation induced by a vast range of sub-lethal H2O2 concentrations, (b) inactivation of GAPDH cannot be considered a sensitive biomarker of H2O2-induced oxidation in vivo. Since GAPDH inactivation only occurs at cell death-inducing high H2O2 doses, GAPDH-dependent rerouting of carbohydrate flux is probably important merely in pathophysiological situations. This work highlights the importance of studying H2O2-induced oxidative stress using concentrations closer to the physiological for determining the importance of protein oxidation phenomena in the regulation of cellular metabolism.

A data sequence acquired at Mt. Etna during the 2002–2003 eruption highlights the potential of continuous gravity observations as a tool to monitor and study active volcanoes

Abstract A 2.5-month long gravity sequence, encompassing the starting period of the 2002–2003 Etna eruption and coming from a summit station only 1 km away from the new fractures, is presented and discussed. The sequence comprises four hours-long anomalies that have a great chance to reflect mass redistributions linked to the ensuing activity. In particular, the start of the eruptive activity on the northeastern flank was marked by a gravity decrease as strong as about 400 μGal, which reverted soon afterwards. This strong decrease/increase anomaly is interpreted as the opening, by tectonic forces, of a fracture system along the Northeastern Rift of Mt. Etna, followed by an intrusion of magma from the central conduit to the new fractures. They were used by the intruding magma as a path to the eruptive vents at lower elevations. Afterwards, on three occasions, in November and December 2002, 6–12 h-lasting gravity decreases, with amplitude ranging between 10 and 30 μGal, were observed simultaneously with increases in the amplitude of the volcanic tremor from four seismic stations. A correlation analysis, between the gravity signal and the overall spectral amplitude of each tremor sequence is performed over the 7 November–9 December period. A marked anti-correlation is found over each contemporaneous gravity decrease/tremor increase, while, over the rest of the investigated period, the correlation is negligible. Accordingly, a joint source is inferred to have acted during the occurrence of the three common anomalies. On the grounds of some volcanological observations spanning the period covered by our analysis, we propose the temporary accumulation of a gas cloud at some level within the plumbing system of the volcano to have acted as a joint source. The present work is a further evidence of the potential of continuous gravity observations as a tool to monitor and study active volcanoes and encourages their employment in spite of the difficulty of running spring gravimeters in a continuous fashion under the adverse conditions normally encountered on the summit zone of an active volcano.

Group I but not Group II NPV induces antiviral effects in mammalian cells

Nucleopolyhedrovirus (NPV) is divided into Group I and Group II based on the phylogenetic analysis. It has been reported that Group I NPVs such as Autographa californica multiple NPV (AcMNPV) can transduce mammalian cells, while Group II NPVs such as Helicoverpa armigera single NPV (HaSNPV) cannot. Here we report that AcMNPV was capable of stimulating antiviral activity in human hepatoma cells (SMMC-7721) manifested by inhibition of Vesicular Stomatitis virus (VSV) replication. In contrast, the HaSNPV and the Spodoptera exigua multiple NPV (SeMNPV) of group II had no inhibitory effect on VSV. Recombinant AcMNPV was shown to induce interferons alpha/beta even in the absence of transgene expression in human SMMC-7721 cells, while it mediated transgene expression in BHK and L929 mammalian cells without an ensuing antiviral activity.

Transhumance livestock production in the Northern Areas of Pakistan: Nutritional inputs and productive outputs

The Northern Areas of Pakistan form a mountainous, semi-arid region in which subsistence mixed farming is the predominant economic activity for the majority of the population, which numbers around 1 million. Following a period of relative isolation, construction of the Karakoram Highway and the ensuing development activity have been catalysts for rapid infrastructural and social change over the last two decades. In the study reported here, feed resources for the livestock enterprise, which is largely made up of cattle, goats and sheep, were studied in detail over the course of a single winter feeding season. Productive outputs including liveweight change, milk production and reproductive performance were also quantified over a full year. The aim of the study was to provide a quantitative description of the system and to assess the extent to which proximity to a major highway influenced livestock husbandary. Six villages across the region were selected for study as part of a 2 × 3 factorial design with one village per cell of the study design. Factors consisted of two geographical transects and three agro-ecological zones. Transects were the Karakoram Highway (KKH) transect which enjoyed relatively good transport infrastructure and the Gilgit Ghizer Region (GGR) transect where infrastructure was more limited. Agro-ecological zones were the single, transitional and double cropping zones. One village per transect from each of the three main agro-ecological zones was chosen for study with 6–7 households within each village studied. Results showed that feed resources per household did not vary significantly according to transect or zone but cattle numbers per household were higher in the GGR transect than in the KKH transect indicating a heavier reliance on subsistence livestock production in this transect. Live weight and body condition of livestock in the Northern Areas changed markedly over the annual cycle. Losses of live weight were in the order of 10% over winter while summer gains during the summer season averaged 35% of initial live weight. There were differences between transects, with animals in the KKH gaining less weight in summer but showing higher milk yield (in cattle) and better reproductive performance. The results indicate a typical system of smallholder livestock production with heavy reliance on cereal by-products, a mix of livestock species and a relative scarcity of stored feed resources relative to overall livestock holdings. This study also suggests that proximity to the main highway running through the Northern Areas is associated with a reduced but more feed-efficient livestock production system.

Characterization of early plasma concentrations of midazolam in pigs after administration by an autoinjector.

The treatment of organophosphate-induced poisoning is based mainly on atropine and an oxime. Prompt anticonvulsive intervention is usually also required to terminate the ensuing seizure activity and to prevent delayed permanent brain damage. Midazolam, a water-soluble benzodiazepine agonist, has the advantage of rapid absorption following intramuscular administration. In mass casualty situations, the availability of an autoinjector, filled with midazolam, might be a further advantage. In the present study, the plasma pharmacokinetics of midazolam after administration by an autoinjector was compared with conventional intramuscular (i.m.) administration in two groups of four pigs each. During the first 15 min after injection, significantly higher plasma concentrations of midazolam were detected following autoinjector administration, compared with the i.m. injection. The physiological reflection of the accelerated midazolam absorption was a marked reduction in the time interval required for muscle relaxation, induced by midazolam. It is concluded that a midazolam autoinjector might be helpful in the mass casualty scenario following organophosphate poisoning.

Role of surfactant structure on surface and foaming properties

The influence of surfactant structure on interface properties was estimated from measurements of the static and dynamic surface tension and the interface complex modulus, as obtained from an image analysis technique based on the oscillating bubble method. A simplified kinetic model of surfactants molecular adsorption at the gas–liquid interface was introduced and the rate of adsorption was determined from measurements of the dynamic surface tension. The mean life time of foams generated from bubbling air through different surfactant solutions was measured using a modified Bikerman device. The major conclusion arising from this study, as expected from basic considerations, was that the chain length of the hydrophobic part of the surfactant plays a determining role with respect to both the kinetic migration to the interfaces and the ensuing surface activity, as shown by the extent of phase delay and foam stability.

Changing Conceptions of Human Intelligence and Reasoning: Implications for the Classroom

This article lays out an alternative view of that which enables human competence, which is framed by complexity theory and draws on connectionism, and situated cognition. It suggests that developing the implications of such a view can provide the basis of a more fully articulated theory of instruction and that such a reconceptualisation may benefit the practice of education. What educators are ultimately after, I am convinced, is that-which-enables-competent-action. It is the desire to equip our students with what they will need to navigate successfully the world that motivates a teacher's activity. But that motivation is mediated by cultural beliefs as to just what enables competent action. The traditional framework shapes and constrains what is seen as sensible and even possible in the practice of education in problematic ways. Education has long identified `intelligence' as the basic capacity for competence and `reasoning' as the activity that generates competence. Historically we have tended to see these two as reciprocal: intelligence is the ability to reason, especially to reason formally, and formal rationality is the expression of intelligence. This linkage has led to particular forms of schooling based on derived notions of learning, thought, memory, and perception. But newer conceptions of our humanity (and not a few older ones, such as those of Dewey, Piaget, Wittgenstein, Merleau-Ponty, Vygotsky, and James) lead us away from the traditional set of ideas and towards a conception both more diffuse and more complex of what `enablers' of our action might be. Where the traditional framework focused attention on the individual, more recent formulations blur the boundaries between self and biology on the one hand and between self and world on the other. As a consequence, we are asked to confront a wider range of phenomena when we conceive of what happens during learning. Educational practices and educational theory have been shaped by (and have shaped) a traditional view of the mind. The traditional image of mind as a logic machine, instituted by Descartes and endorsed by the rationalists of the Enlightenment, has reached its logical completion in the popular conception of the computer and in the activity of the field of artificial intelligence (Al). Disregarding Descartes' dualism, Al researchers attempt to build machines that, logically enough, think. They have failed. But their failure, though predictable in outline by those who attend to the successes and failures of education in enacting a logical image of students, is wryly instructive in detail. Logicist images of mind have failed because they are too rigid and because they presume a complete knowledge of context before effective action can be taken (Dreyfus & Dreyfus, 1987). These two factors are related. The rigidity of AI's `intelligence' is due to the logical image that constitutes its basis. Objects of knowledge are known by their necessary and sufficient features and are related by the implicative rules of logic. For example: Axiom A and Fact B, related Logically, yield Implication C. But to be certain of the answer one must have all the facts right, for any difference that might make a difference in action must be described before deduction and the ensuing activity occur. The representational scheme of logicism is too unwieldy to be of much use in a world characterised by limited knowledge and categories that function by `family resemblance' (Triche, 1994; Wittgenstein, 1953). The world that we act within is a very different place. We recognise the educational expression of this theoretical position in the assumption that education consists of the acquisition of learning `objects'--facts and procedural rules that can be understood as facts. Such a position makes sensible the back-to-basics movement in many countries which emphasises the possession of content, understood as facts and basic procedures prior to and usually in place of any ability to put a student's understanding to use. …

Long T methamphetamine schedules produce circadian ensuing drug activity in rats

Eight female Sprague–Dawley rats were housed in isolated continuous 24-h/day environments under conditions of constant dim light and a rate-limited feeding schedule. Following 2 months of free-running activity, all animals were administered methamphetamine (MA) i.p. (2 mg/kg) once every 31 h for 24 injection cycles. Average wave forms of wheel-running activity showed that animals did not anticipate the 31-h schedule of MA injections, but rather displayed circadian ensuing drug activity (CEDA) between 24 and 28 h following the injections. Post-injection meals failed to meet reliably the threshold necessary to achieve food-engendered anticipatory or ensuing activity. Cosinor analysis showed that the intensity of CEDA was strongly influenced by the relative phase of the free-running rhythm. CEDA was moderately influenced by the size of the post-injection bout of activity. Because injection times rotated daily throughout local time without repeating a time of day, CEDA resulting from a long T schedule of MA administration appeared to be based on one-trial resetting of a circadian-related mechanism by a major drug of abuse.

Meal-synchronized CEA in rats: effects of meal size, intragastric feeding, and subdiaphragmatic vagotomy.

Within a feeding schedule of intermittent food access, large meals have the ability to induce activity at the same time the next day [circadian ensuing activity (CEA)]. In these experiments, we evaluated the minimum meal size necessary to induce CEA and whether oral-pharyngeal factors and afferent vagal activity played necessary roles in the induction of the underlying process. In experiment 1, every 33 h rats were given two meals separated by a 2-h interval. The size of the first meal was varied, while total intake every feeding cycle was held constant. When the initial meal was <10 g (34 kcal) CEA occurred later, indicating that such a meal size was subthreshold for inducing CEA. In experiment 2, rats were given intragastric (IG) meals every 33 h, before and after complete subdiaphragmatic vagotomy. IG nutrient meals induced CEA, indicating that extensive oral-pharyngeal experience was not necessary for CEA induction. CEA occurred in vagotomized rats but, compared with intact rats, appeared to occur later relative to nutrient infusion, indicating that afferent vagal activity may be sufficient but not necessary to induce CEA.

Meal-Engendered Circadian-Ensuing Activity in Rats

Large meals scheduled at greater-than-circadian periods (such as T = 31 h) tend to elicit enhanced activity approximately 24 h subsequent to receipt. These studies characterized the process responsible for this meal-engendered “circadian ensuing activity” (meal CEA). Female Sprague–Dawley rats were housed in stations containing a running wheel, pellet dispenser, and lights. Young, middle-aged, or suprachiasmatic–nucleus (SCN)-lesioned rats were given two 1-h meals every 31 or 34 h. Meals were separated by alternating short and long fasts. Most young intact rats engaged in enhanced activity approximately 24 h subsequent to the start of the two-meal series. This circadian ensuing activity underwent large, abrupt daily displacements in response to daily meal delays, was manifested to some degree at all times of day, had an amplitude that was modulated by circadian time of day, was attenuated in middle-aged rats, was evident in SCN-lesioned rats, and oscillated following termination of the feeding schedule. A single experience with food at a novel time of day can “reset” an SCN-independent oscillating process responsible for a circadian activity pattern. CEA has features not readily accommodated by present models of “food-anticipatory activity.” The readiness with which the process can be reset implies a keen sensitivity to shifts in the time of food availability but could also produce aberrant behavioral patterns. A T >> 24-h feeding schedule appears to be an ideal procedure with which to study the specific food-related factors responsible for resetting circadian processes and producing a subsequent reallocation of daily activity.