Light intensity alters the effects of light-induced circadian disruption on glucose and lipid metabolism in mice

Circadian disruption induced by rotating light cycles has been linked to metabolic disorders. However, how the interaction of light intensity and light cycle affects metabolism under different diets remains to be explored. Eighty mice were first randomly stratified into the low-fat diet (LFD, n = 40) or high-fat diet (HFD, n = 40) groups. Each group was further randomly subdivided into four groups (n = 8-12 per group) in terms of different light intensities [lower (LI, 78 lx) or higher intensity (HI, 169 lx)] and light cycles [12-h light:12-h dark cycle or circadian-disrupting (CD) light cycle consisting of repeated 6-h light phase advancement]. Body weight was measured weekly. At the end of the 16-wk experiment, mice were euthanized for serum and pathological analysis. Glucose and insulin tolerance tests were performed during the last 2 wk. The CD cycle increased body weight gain, adipocyte area, glucose intolerance, and insulin resistance of LFD as well as HFD mice under HI but not LI condition. Moreover, the serum and hepatic triglyceride levels increased with LFD-HI treatment, regardless of light cycle. In addition, the CD cycle improved lipid and glucose metabolism under HFD-LI condition. In summary, the detrimental effects of the CD cycle on metabolism were alleviated under LI condition, especially in HFD mice. These results indicate that modulating light intensity is a potential strategy to prevent the negative metabolic consequences associated with jet lag or shift work.NEW & NOTEWORTHY Glucose and lipid homeostasis is altered by the CD cycles in a light-intensity-dependent manner. Lower-intensity light reverses the negative metabolic effects of the CD cycles, especially under HFD feeding. The interaction of light intensity and light cycle on metabolism is independent of energy intake and eating pattern. Glucose metabolic disorders caused by rotating light cycles occur along with compensatory β-cell mass expansion.

High-Dose Irradiation Inhibits Motility and Induces Autophagy in Caenorhabditis elegans

Radiation damages many cellular components and disrupts cellular functions, and was previously reported to impair locomotion in the model organism Caenorhabditis elegans. However, the response to even higher doses is not clear. First, to investigate the effects of high-dose radiation on the locomotion of C. elegans, we investigated the dose range that reduces whole-body locomotion or leads to death. Irradiation was performed in the range of 0-6 kGy. In the crawling analysis, motility decreased after irradiation in a dose-dependent manner. Exposure to 6 kGy of radiation affected crawling on agar immediately and caused the complete loss of motility. Both γ-rays and carbon-ion beams significantly reduced crawling motility at 3 kGy. Next, swimming in buffer was measured as a motility index to assess the response over time after irradiation and motility similarly decreased. However, swimming partially recovered 6 h after irradiation with 3 kGy of γ-rays. To examine the possibility of a recovery mechanism, in situ GFP reporter assay of the autophagy-related gene lgg-1 was performed. The fluorescence intensity was stronger in the anterior half of the body 7 h after irradiation with 3 kGy of γ-rays. GFP::LGG-1 induction was observed in the pharynx, neurons along the body, and the intestine. Furthermore, worms were exposed to region-specific radiation with carbon-ion microbeams and the trajectory of crawling was measured by image processing. Motility was lower after anterior-half body irradiation than after posterior-half body irradiation. This further supported that the anterior half of the body is important in the locomotory response to radiation.

Does a Red House Affect Rhythms in Mice with a Corrupted Circadian System?

The circadian rhythms of body functions in mammals are controlled by the circadian system. The suprachiasmatic nucleus (SCN) in the hypothalamus orchestrates subordinate oscillators. Time information is conveyed from the retina to the SCN to coordinate an organism's physiology and behavior with the light/dark cycle. At the cellular level, molecular clockwork composed of interlocked transcriptional/translational feedback loops of clock genes drives rhythmic gene expression. Mice with targeted deletion of the essential clock gene Bmal1 (Bmal1-/-) have an impaired light input pathway into the circadian system and show a loss of circadian rhythms. The red house (RH) is an animal welfare measure widely used for rodents as a hiding place. Red plastic provides light at a low irradiance and long wavelength-conditions which affect the circadian system. It is not known yet whether the RH affects rhythmic behavior in mice with a corrupted circadian system. Here, we analyzed whether the RH affects spontaneous locomotor activity in Bmal1-/- mice under standard laboratory light conditions. In addition, mPER1- and p-ERK-immunoreactions, as markers for rhythmic SCN neuronal activity, and day/night plasma corticosterone levels were evaluated. Our findings indicate that application of the RH to Bmal1-/- abolishes rhythmic locomotor behavior and dampens rhythmic SCN neuronal activity. However, RH had no effect on the day/night difference in corticosterone levels.

Radiofrequency electromagnetic radiation-induced behavioral changes and their possible basis

The primary objective of mobile phone technology is to achieve communication with any person at any place and time. In the modern era, it is impossible to ignore the usefulness of mobile phone technology in cases of emergency as many lives have been saved. However, the biological effects they may have on humans and other animals have been largely ignored and not been evaluated comprehensively. One of the reasons for this is the speedy uncontrollable growth of this technology which has surpassed our researching ability. Initiated with the first generation, the mobile telephony currently reaches to its fifth generation without being screened extensively for any biological effects that they may have on humans or on other animals. Mounting evidences suggest possible non-thermal biological effects of radiofrequency electromagnetic radiation (RF-EMR) on brain and behavior. Behavioral studies have particularly concentrated on the effects of RF-EMR on learning, memory, anxiety, and locomotion. The literature analysis on behavioral effects of RF-EMR demonstrates complex picture with conflicting observations. Nonetheless, numerous reports suggest a possible behavioral effect of RF-EMR. The scientific findings about this issue are presented in the current review. The possible neural and molecular mechanisms for the behavioral effects have been proposed in the light of available evidences from the literature.

Artificial light pollution at night (ALAN) disrupts the distribution and circadian rhythm of a sandy beach isopod

Coastal habitats, in particular sandy beaches, are becoming increasingly exposed to artificial light pollution at night (ALAN). Yet, only a few studies have this far assessed the effects of ALAN on the species inhabiting these ecosystems. In this study we assessed the effects of ALAN on Tylos spinulosus, a prominent wrack-consumer isopod living in sandy beaches of north-central Chile. This species burrows in the sand during daylight and emerges at night to migrate down-shore, so we argue it can be used as a model species for the study of ALAN effects on coastal nocturnal species. We assessed whether ALAN alters the distribution and locomotor activity of this isopod using a light system placed in upper shore sediments close to the edge of the dunes, mimicking light intensities measured near public lighting. The response of the isopods was compared to control transects located farther away and not exposed to artificial light. In parallel, we measured the isopods' locomotor activity in the laboratory using actographs that recorded their movement within mesocosms simulating the beach surface. Measurements in the field indicated a clear reduction in isopod abundance near the source of the light and a restriction of their tidal distribution range, as compared to control transects. Meanwhile, the laboratory experiments showed that in mesocosms exposed to ALAN, isopods exhibited reduced activity and a circadian rhythm that was altered and even lost after a few days. Such changes with respect to control mesocosms with a natural day/night cycle suggest that the changes observed in the field were directly related to a disruption in the locomotor activity of the isopods. All together these results provide causal evidence of negative ALAN effects on this species, and call for further research on other nocturnal sandy beach species that might become increasingly affected by ALAN.

The circadian activity rhythm is reset by nanowatt pulses of ultraviolet light

The circadian pacemaker synchronizes to the Earth's rotation by tracking step-by-step changes in illumination that occur as the sun passes the horizon. While twilight progressions of irradiance and colour are considered important stimuli in this process, comparably less thought has been given to the possibility that ultraviolet A (UVA) radiation might actually play a more formative role given its evolutionary significance in shaping 24 h timekeeping. Here, we show that Drosophila activity rhythms can be phase-shifted by UVA light at an energy range seated well below that of the visible spectrum. Because the energy threshold for this resetting matches the incident amount of UVA on the human retina at twilight, our results suggest that UVA light has the potential to function as a similar time cue in people.

Data-driven analysis of motor activity implicates 5-HT2A neurons in backward locomotion of larval Drosophila

Rhythmic animal behaviors are regulated in part by neural circuits called the central pattern generators (CPGs). Classifying neural population activities correlated with body movements and identifying the associated component neurons are critical steps in understanding CPGs. Previous methods that classify neural dynamics obtained by dimension reduction algorithms often require manual optimization which could be laborious and preparation-specific. Here, we present a simpler and more flexible method that is based on the pre-trained convolutional neural network model VGG-16 and unsupervised learning, and successfully classifies the fictive motor patterns in Drosophila larvae under various imaging conditions. We also used voxel-wise correlation mapping to identify neurons associated with motor patterns. By applying these methods to neurons targeted by 5-HT2A-GAL4, which we generated by the CRISPR/Cas9-system, we identified two classes of interneurons, termed Seta and Leta, which are specifically active during backward but not forward fictive locomotion. Optogenetic activation of Seta and Leta neurons increased backward locomotion. Conversely, thermogenetic inhibition of 5-HT2A-GAL4 neurons or application of a 5-HT2 antagonist decreased backward locomotion induced by noxious light stimuli. This study establishes an accelerated pipeline for activity profiling and cell identification in larval Drosophila and implicates the serotonergic system in the modulation of backward locomotion.

Cerebral impact of prenatal irradiation by 131I: an experimental model of clinical neuroradioembryological effects

Human brain in prenatal period is a most vulnerable to ionizing radiation body structure. Unlike atomic bombings or radiological interventions in healthcare leading at most to external irradiation the intensive internal exposure may occur upon nuclear reactor accidents followed by substantial release and fallout of radioactive 131I. The latter can lead to specific neuroradioembryological effects.

OBJECTIVE

To create an experimental model of prenatal cerebral radiation effects of 131I in human and to determine the experimental and clinical neuroradioembryological effects.Study object. The neuroradioembryological effects in Vistar rats exposed to 131I in prenatal period. Nervous system status and mental status in 104 persons exposed to ionizing radiation in utero due to the ChNPP accident and the same in 78 not exposed subjects.

METHODS

Experimental i.e. behavioral techniques, including the spontaneous locomotive, exploratory activity and learning ability assessment, clinical i.e. neuropsychiatric, neuro and psychometric, neuropsychological, neurophys iological methods, both with dosimetric and statistical methods were applied.

RESULTS

Intrauterine irradiation of Wistar rats by 131I was simulated on a model of one time oral 27.5 kBq radionu clide administration in the mid gestation period (0.72±0.14 Gy fetal thyroid dose), which provides extrapolation of neuroradioembryological effects in rats to that in humans exposed to intrauterine radiation as a result of the Chornobyl catastrophe. Abnormalities in behavioral reactions and decreased output of conditioned reflex reactions identified in the 10 month old rats suggest a deterioration of cerebral cognition in exposed animals. Specific cog nitive deficit featuring a disharmonic intellectual development through the relatively decreased verbal intelligence versus relative increase of nonverbal one is remained in prenatally exposed persons. This can indicate to dysfunc tion of cortical limbic system with especial involvement of a dominant hemisphere hippocampus. Decreased theta band spectral power (4-7 Hz range) of cerebral bioelectrical activity in the left frontotemporal area is suggestive of hippocampal dysfunction mainly in dominant hemisphere of prenatally irradiated persons. Disorders of hippocam pal neurogenesis due to prenatal exposure by radioactive iodine can be a biologic basis here. Innovative approach es in social adaptation, psychoprophylaxis and psychorehabilitation involve the maximum effective application and development of just the most developed psychological and cognitive abilities in survivors.

Evidence of Zinc in Affording Protection Against X-Ray-Induced Brain Injury in Rats

In the present world, X-rays have been regarded as one of the most efficient tools in medicine, industry and research. On the contrary, extensive human exposure to these rays is responsible for causing detrimental effects on physiological system. The aim of the present study was to investigate the role of zinc (Zn), if any, in mitigating the adverse effects induced by fractionated X-irradiation on rat brain. Female Sprague-Dawley rats weighing 170-200 g were divided into four different groups viz.: (a) normal control, (b) X-irradiated (21Gy), (c) zinc treated (227 mg/L in drinking water) and (d) X-irradiated + zinc treated. The skulls of animals belonging to groups (b) and (d) were exposed to X-rays in 30 fractions. Each fraction delivered a radiation dose of 70 rads, and rats were exposed to two fractions every day for 15 days, consecutively. X-ray treatment resulted in significant alterations in the neurobehavior, neurotransmitter levels and neuro-histoarchitecture of rats, whereas zinc co-treatment with X-rays resulted in significant improvement in these parameters. X-ray exposure also caused a significant increase in the levels of lipid peroxidation as well as activities of catalase and superoxide dismutase, which however were decreased upon simultaneous Zn treatment. On the contrary, X-ray treatment down-regulated the glutathione system, which were found to be up-regulated by zinc co-treatment. Further, protein expressions of p53 and NF-ҚB were found to be significantly elevated after X-irradiation, which were reversed following Zn supplementation. Hence, Zn seems to be an effective agent in mitigating the detrimental effects caused by exposure to X-rays.

Selective changes in locomotor activity in mice due to low-intensity microwaves amplitude modulated in the EEG spectral domain

Despite the numerous benefits of microwave applications in our daily life, microwaves were associated with diverse neurological complaints such as headaches and impaired sleep patterns, and changes in the electroencephalogram (EEG). To which extent microwaves influence the brain function remains unclear. This exploratory study assessed the behavior and neurochemistry in mice immediately or 4weeks after a 6-day exposure to low-intensity 10-GHz microwaves with an amplitude modulation (AM) of 2 or 8Hz. These modulation frequencies of 2 and 8Hz are situated within the delta and theta-alpha frequency bands in the EEG spectrum and are associated with sleep and active behavior, respectively. During these experiments, the specific absorbance rate was 0.3W/kg increasing the brain temperature with 0.23°C. For the first time, exposing mice to 8-Hz AM significantly reduced locomotor activity in an open field immediately after exposure which normalized after 4weeks. This in contrast to 2-Hz AM which didn't induce significant changes in locomotor activity immediately and 4weeks after exposure. Despite this difference in motor behavior, no significant changes in striatal dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) levels and DOPAC/DA turnover nor in cortical glutamate (GLU) concentrations were detected. In all cases, no effects on motor coordination on a rotarod, spatial working memory, anxiety nor depressive-like behavior were observed. The outcome of this study indicates that exposing mice to low-intensity 8-Hz AM microwaves can alter the locomotor activity in contrast to 2-Hz AM which did not affect the tested behaviors.

Radioprotective effect of ursolic acid in radiation-induced impairment of neurogenesis, learning and memory in adolescent BALB/c mouse

The effect of acute irradiation with 5Gy or fractionated exposure with 0.5Gy continuously for 10days (a total dose of 5Gy) was evaluated in an immature BALB/c mouse model. Radioprotective effect of ursolic acid (at 25mg/kg/daily administered 1h after acute or each of fractionated irradiations, and continuously for 30days) was also investigated. We found that both acute and fractionated irradiation at a total dose of 5Gy did not induce any mortality within 30days after exposure to postnatal day 26 (P26) BALB/c mice, but reduced animal weigh gain in the first few weeks. At 90days after irradiation, the weight of animals with acute irradiation was still significantly lower than the control group; no significant difference though was observed for those fractionatedly exposed mice compared to the control group. Behavioral tests indicated that acute irradiation at 5Gy induced deficits in learning and memory in the contextual fear conditioning test. The memory for novel object recognition was also impaired. Similar changes were not observed in mice with fractionated irradiation. Immunohistochemical study demonstrated clearly that acute and fractionated irradiations induced impairment of neurogenesis in the subgranular zone (SGZ) of the dentate gyrus although fractionated exposure induced much lesser loss of newly generated neurons. Ursolic acid administered at 25mg/kg/daily for 30days after irradiation greatly improved acute irradiation-induced deficits in contextual learning and memory and in novel object recognition memory although it exacerbated radiation-induced reduction of neurogenesis in SGZ.

Egocentric and allocentric representations in auditory cortex

A key function of the brain is to provide a stable representation of an object's location in the world. In hearing, sound azimuth and elevation are encoded by neurons throughout the auditory system, and auditory cortex is necessary for sound localization. However, the coordinate frame in which neurons represent sound space remains undefined: classical spatial receptive fields in head-fixed subjects can be explained either by sensitivity to sound source location relative to the head (egocentric) or relative to the world (allocentric encoding). This coordinate frame ambiguity can be resolved by studying freely moving subjects; here we recorded spatial receptive fields in the auditory cortex of freely moving ferrets. We found that most spatially tuned neurons represented sound source location relative to the head across changes in head position and direction. In addition, we also recorded a small number of neurons in which sound location was represented in a world-centered coordinate frame. We used measurements of spatial tuning across changes in head position and direction to explore the influence of sound source distance and speed of head movement on auditory cortical activity and spatial tuning. Modulation depth of spatial tuning increased with distance for egocentric but not allocentric units, whereas, for both populations, modulation was stronger at faster movement speeds. Our findings suggest that early auditory cortex primarily represents sound source location relative to ourselves but that a minority of cells can represent sound location in the world independent of our own position.

Influence of temperature on daily locomotor activity in the crab Uca pugilator

Animals living in the intertidal zone are exposed to prominent temperature changes. To cope with the energetic demands of environmental thermal challenges, ectotherms rely mainly on behavioral responses, which may change depending on the time of the day and seasonally. Here, we analyze how temperature shapes crabs’ behavior at 2 different times of the year and show that a transition from constant cold (13.5°C) to constant warm (17.5°C) water temperature leads to increased locomotor activity levels throughout the day in fiddler crabs (Uca pugilator) collected during the summer. In contrast, the same transition in environmental temperature leads to a decrease in the amplitude of the daily locomotor activity rhythm in crabs collected during the winter. In other words, colder temperatures during the cold season favor a more prominent diurnal behavior. We interpret this winter-summer difference in the response of daily locomotor activity to temperature changes within the framework of the circadian thermoenergetics hypothesis, which predicts that a less favorable energetic balance would promote a more diurnal activity pattern. During the winter, when the energetic balance is likely less favorable, crabs would save energy by being more active during the expected high-temperature phase of the day—light phase—and less during the expected low-temperature phase of the day—dark phase. Our results suggest that endogenous rhythms in intertidal ectotherms generate adaptive behavioral programs to cope with thermoregulatory demands of the intertidal habitat.

Adult Tea Green Leafhoppers, Empoasca onukii (Matsuda), Change Behaviors under Varying Light Conditions

Insect behaviors are often influenced by light conditions including photoperiod, light intensity, and wavelength. Understanding pest insect responses to changing light conditions may help with developing alternative strategies for pest control. Little is known about the behavioral responses of leafhoppers (Hemiptera: Cicadellidae) to light conditions. The behavior of the tea green leafhopper, Empoasca onukii Matsuda, was examined when exposed to different light photoperiods or wavelengths. Observations included the frequency of locomotion and cleaning activities, and the duration of time spent searching. The results suggested that under normal photoperiod both female and male adults were generally more active in darkness (i.e., at night) than in light. In continuous darkness (DD), the locomotion and cleaning events in Period 1 (7:00-19:00) were significantly increased, when compared to the leafhoppers under normal photoperiod (LD). Leafhoppers, especially females, changed their behavioral patterns to a two day cycle under DD. Under continuous illumination (continuous quartz lamp light, yellow light at night, and green light at night), the activities of locomotion, cleaning, and searching were significantly suppressed during the night (19:00-7:00) and locomotion activities of both females and males were significantly increased during the day (7:00-19:00), suggesting a shift in circadian rhythm. Our work suggests that changes in light conditions, including photoperiod and wavelength, can influence behavioral activities of leafhoppers, potentially affecting other life history traits such as reproduction and development, and may serve as a method for leafhopper behavioral control.

White - cGMP Interaction Promotes Fast Locomotor Recovery from Anoxia in Adult Drosophila

Increasing evidence indicates that the white (w) gene in Drosophila possesses extra-retinal functions in addition to its classical role in eye pigmentation. We have previously shown that w+ promotes fast and consistent locomotor recovery from anoxia, but how w+ modulates locomotor recovery is largely unknown. Here we show that in the absence of w+, several PDE mutants, especially cyclic guanosine monophosphate (cGMP)-specific PDE mutants, display wildtype-like fast locomotor recovery from anoxia, and that during the night time, locomotor recovery was light-sensitive in white-eyed mutant w1118, and light-insensitive in PDE mutants under w1118 background. Data indicate the involvement of cGMP in the modulation of recovery timing and presumably, light-evoked cGMP fluctuation is associated with light sensitivity of locomotor recovery. This was further supported by the observations that w-RNAi-induced delay of locomotor recovery was completely eliminated by upregulation of cGMP through multiple approaches, including PDE mutation, simultaneous overexpression of an atypical soluble guanylyl cyclase Gyc88E, or sildenafil feeding. Lastly, prolonged sildenafil feeding promoted fast locomotor recovery from anoxia in w1118. Taken together, these data suggest that a White-cGMP interaction modulates the timing of locomotor recovery from anoxia.

Interaction of ARF-1.1 and neuronal calcium sensor-1 in the control of the temperature-dependency of locomotion in Caenorhabditis elegans

Neuronal calcium sensor-1 (NCS-1) mediates changes in cellular function by regulating various target proteins. Many potential targets have been identified but the physiological significance of only a few has been established. Upon temperature elevation, Caenorhabditis elegans exhibits reversible paralysis. In the absence of NCS-1, worms show delayed onset and a shorter duration of paralysis. This phenotype can be rescued by re-expression of ncs-1 in AIY neurons. Mutants with defects in four potential NCS-1 targets (arf-1.1, pifk-1, trp-1 and trp-2) showed qualitatively similar phenotypes to ncs-1 null worms, although the effect of pifk-1 mutation on time to paralysis was considerably delayed. Inhibition of pifk-1 also resulted in a locomotion phenotype. Analysis of double mutants showed no additive effects between mutations in ncs-1 and trp-1 or trp-2. In contrast, double mutants of arf-1.1 and ncs-1 had an intermediate phenotype, consistent with NCS-1 and ARF-1.1 acting in the same pathway. Over-expression of arf-1.1 in the AIY neurons was sufficient to rescue partially the phenotype of both the arf-1.1 and the ncs-1 null worms. These findings suggest that ARF-1.1 interacts with NCS-1 in AIY neurons and potentially pifk-1 in the Ca(2+) signaling pathway that leads to inhibited locomotion at an elevated temperature.

Behavioral Thermoregulation and Trade-Offs in Juvenile Lobster Homarus americanus

Water temperature influences the behavior and distribution patterns of both larval and adult American lobster Homarus americanus. However, very little is known about the responses of juvenile lobsters. The juvenile life stage is a critical period; high levels of mortality, combined with specific behavioral responses, can disconnect larval settlement from patterns of abundance of adults. We assessed behavioral thermoregulation in juvenile lobsters, and determined how thermal preferences can be altered by the presence of shelter and food. Juvenile lobsters avoided temperatures higher than 20 °C and lower than 8 °C, and had a mean temperature preference of 16.2 ± 1 °C. This preference was unaffected by prior acclimation, origin (laboratory-raised or wild), or size. When the animals were subjected to a temperature change (5-20 °C), activity rates peaked at 15 °C, and remained stable thereafter. Activity rates did not change when a shelter was added. The addition of food resulted in an increase in activity associated with food handling. When juvenile lobsters were offered a choice between temperature, shelter, and food, they always chose the environment with a shelter, even when it was in a thermally unfavorable temperature. Juveniles also spent more time in a thermally unfavorable environment when food was present; however, acquisition of a shelter was prioritized over food. Although juveniles had a similar thermal preference to adults, they are more vulnerable to predation; the innate shelter-seeking behavior of juveniles overrode their thermal preference. While temperature is an important environmental factor affecting the physiology, distribution, and growth of aquatic ectotherms, our findings suggest that trade-off behaviors occur in order to maintain optimal fitness and survival of the individual.

Optogenetic Modulation of Locomotor Activity on Free-Behaving Rats

The technology of optogenetics provides a new method to modulate neural activity with spatial specificity and millisecond-temporal scale. This nonelectrical modulation method also gives chance for simultaneous electrophysiological recording during stimulations. Here, we describe our locomotor activity modulation on free-behaving rats using optogenetic techniques. The target sites of the rat brain were dorsal periaqueductal gray (dPAG) and ventral tegmental area (VTA) for the modulation of defensive and reward behaviors, respectively.

Feverlike Temperature is a Virulence Regulatory Cue Controlling the Motility and Host Cell Entry of Typhoidal Salmonella

Human infection with typhoidal Salmonella serovars causes a febrile systemic disease, termed enteric fever. Here we establish that in response to a temperature equivalent to fever (39 °C-42 °C) Salmonella enterica serovars Typhi, Paratyphi A, and Sendai significantly attenuate their motility, epithelial cell invasion, and uptake by macrophages. Under these feverlike conditions, the residual epithelial cell invasion of S. Paratyphi A occurs in a type III secretion system (T3SS) 1-independent manner and results in restrained disruption of epithelium integrity. The impaired motility and invasion are associated with down-regulation of T3SS-1 genes and class II and III (but not I) of the flagella-chemotaxis regulon. In contrast, we demonstrate up-regulation of particular Salmonella pathogenicity island 2 genes (especially spiC) and increased intraepithelial growth in a T3SS-2-dependent manner. These results indicate that elevated physiological temperature is a novel cue controlling virulence phenotypes in typhoidal serovars, which is likely to play a role in the distinct clinical manifestations elicited by typhoidal and nontyphoidal salmonellae.

Chronic low-dose γ-irradiation of Drosophila melanogaster larvae induces gene expression changes and enhances locomotive behavior

Although radiation effects have been extensively studied, the biological effects of low-dose radiation (LDR) are controversial. This study investigates LDR-induced alterations in locomotive behavior and gene expression profiles of Drosophila melanogaster. We measured locomotive behavior using larval pupation height and the rapid iterative negative geotaxis (RING) assay after exposure to 0.1 Gy γ-radiation (dose rate of 16.7 mGy/h). We also observed chronic LDR effects on development (pupation and eclosion rates) and longevity (life span). To identify chronic LDR effects on gene expression, we performed whole-genome expression analysis using gene-expression microarrays, and confirmed the results using quantitative real-time PCR. The pupation height of the LDR-treated group at the first larval instar was significantly higher (∼2-fold increase in PHI value, P < 0.05). The locomotive behavior of LDR-treated male flies (∼3 - 5 weeks of age) was significantly increased by 7.7%, 29% and 138%, respectively (P < 0.01), but pupation and eclosion rates and life spans were not significantly altered. Genome-wide expression analysis identified 344 genes that were differentially expressed in irradiated larvae compared with in control larvae. We identified several genes belonging to larval behavior functional groups such as locomotion (1.1%), oxidation reduction (8.0%), and genes involved in conventional functional groups modulated by irradiation such as defense response (4.9%), and sensory and perception (2.5%). Four candidate genes were confirmed as differentially expressed genes in irradiated larvae using qRT-PCR (>2-fold change). These data suggest that LDR stimulates locomotion-related genes, and these genes can be used as potential markers for LDR.

Genetic analysis of circadian responses to low frequency electromagnetic fields in Drosophila melanogaster

The blue-light sensitive photoreceptor cryptochrome (CRY) may act as a magneto-receptor through formation of radical pairs involving a triad of tryptophans. Previous genetic analyses of behavioral responses of Drosophila to electromagnetic fields using conditioning, circadian and geotaxis assays have lent some support to the radical pair model (RPM). Here, we describe a new method that generates consistent and reliable circadian responses to electromagnetic fields that differ substantially from those already reported. We used the Schuderer apparatus to isolate Drosophila from local environmental variables, and observe extremely low frequency (3 to 50 Hz) field-induced changes in two locomotor phenotypes, circadian period and activity levels. These field-induced phenotypes are CRY- and blue-light dependent, and are correlated with enhanced CRY stability. Mutational analysis of the terminal tryptophan of the triad hypothesised to be indispensable to the electron transfer required by the RPM reveals that this residue is not necessary for field responses. We observe that deletion of the CRY C-terminus dramatically attenuates the EMF-induced period changes, whereas the N-terminus underlies the hyperactivity. Most strikingly, an isolated CRY C-terminus that does not encode the Tryptophan triad nor the FAD binding domain is nevertheless able to mediate a modest EMF-induced period change. Finally, we observe that hCRY2, but not hCRY1, transformants can detect EMFs, suggesting that hCRY2 is blue light-responsive. In contrast, when we examined circadian molecular cycles in wild-type mouse suprachiasmatic nuclei slices under blue light, there was no field effect. Our results are therefore not consistent with the classical Trp triad-mediated RPM and suggest that CRYs act as blue-light/EMF sensors depending on trans-acting factors that are present in particular cellular environments.

Programming of mice circadian photic responses by postnatal light environment

Early life programming has important consequences for future health and wellbeing. A key new aspect is the impact of perinatal light on the circadian system. Postnatal light environment will program circadian behavior, together with cell morphology and clock gene function within the suprachiasmatic nucleus (SCN) of the hypothalamus, the principal circadian clock in mammals. Nevertheless, it is still not clear whether the observed changes reflect a processing of an altered photic input from the retina, rather than an imprinting of the intrinsic molecular clock mechanisms. Here, we addressed the issue by systematically probing the mouse circadian system at various levels. Firstly, we used electroretinography, pupillometry and histology protocols to show that gross retinal function and morphology in the adult are largely independent of postnatal light experiences that modulate circadian photosensitivity. Secondly, we used circadian activity protocols to show that only the animal's behavioral responses to chronic light exposure, but not to constant darkness or the acute responses to a light stimulus depend on postnatal light experience. Thirdly, we used real-time PER2::LUC rhythm recording to show long-term changes in clock gene expression in the SCN, but also heart, lung and spleen. The data showed that perinatal light mainly targets the long-term adaptive responses of the circadian clock to environmental light, rather than the retina or intrinsic clock mechanisms. Finally, we found long-term effects on circadian peripheral clocks, suggesting far-reaching consequences for the animal's overall physiology.

Detection and selective avoidance of near ultraviolet radiation by an aquatic annelid: the medicinal leech

Medicinal leeches are aquatic predators that inhabit surface waters during daylight and also leave the water where they might be exposed to less screened light. Whereas the leech visual system has been shown to respond to visible light, leeches in the genus Hirudo do not appear to be as negatively phototactic as one might expect in order to avoid potential ultraviolet radiation (UVR)-induced damage. I used high intensity light emitting diodes to test the hypothesis that leeches could detect and specifically avoid near UVR (395-405 nm). Groups of unfed juvenile leeches exhibited a robust negative phototaxis to UVR, but had no behavioral response to blue or red and only a slight negative phototaxis to green and white light. Individual leeches also exhibited a vigorous negative phototaxis to UVR; responding in 100% of trials compared with modest negative responses to visible light (responding in ~8% of the trials). The responses in fed and unfed leeches were comparable for UVR stimuli. The responses depended upon the stimulus site: leeches shortened away from UV light to the head, and extended away from UV light to the tail. Electrophysiological nerve recordings showed that the cephalic eyes responded vigorously to UVR. Additionally, individual leech photoreceptors also showed strong responses to UVR, and a higher-order neuron associated with shortening and rapid behavioral responses, the S-cell, was activated by UVR, on both the head and tail. These results demonstrate that the leech can detect UVR and is able to discriminate behaviorally between UVR and visible light.

Long-term effects of chronic light pollution on seasonal functions of European blackbirds (Turdus merula)

Light pollution is known to affect important biological functions of wild animals, including daily and annual cycles. However, knowledge about long-term effects of chronic exposure to artificial light at night is still very limited. Here we present data on reproductive physiology, molt and locomotor activity during two-year cycles of European blackbirds (Turdus merula) exposed to either dark nights or 0.3 lux at night. As expected, control birds kept under dark nights exhibited two regular testicular and testosterone cycles during the two-year experiment. Control urban birds developed testes faster than their control rural conspecifics. Conversely, while in the first year blackbirds exposed to light at night showed a normal but earlier gonadal cycle compared to control birds, during the second year the reproductive system did not develop at all: both testicular size and testosterone concentration were at baseline levels in all birds. In addition, molt sequence in light-treated birds was more irregular than in control birds in both years. Analysis of locomotor activity showed that birds were still synchronized to the underlying light-dark cycle. We suggest that the lack of reproductive activity and irregular molt progression were possibly the results of i) birds being stuck in a photorefractory state and/or ii) chronic stress. Our data show that chronic low intensities of light at night can dramatically affect the reproductive system. Future studies are needed in order to investigate if and how urban animals avoid such negative impact and to elucidate the physiological mechanisms behind these profound long-term effects of artificial light at night. Finally we call for collaboration between scientists and policy makers to limit the impact of light pollution on animals and ecosystems.

Sublethal exposure to crude oil enhances positive phototaxis in the calanoid copepod Calanus finmarchicus

We investigated the effects of exposure to sublethal concentrations of the water accommodated fraction (WAF) of fresh crude oil on phototactic behavior of the calanoid copepod Calanus finmarchicus (Gunnerus) copepodite stage 5 (C5). Exposure was conducted in closed bottle systems, and behavior was tested in a tailored setup. Exposure times were 24, 48, 72, and 96 h, and the chosen exposure concentration was 25% of the recorded LC50 value for the WAF (309 ± 32 μg/L total hydrocarbon, including 20.37 ± 0.51 μg/L total PAH). The exposure significantly increased the positive phototactic behavior of the copepods after 24 h exposure and a similar significant effect was observed for all exposure durations. Additionally, experiments were conducted with nonexposed copepods with low lipid reserves. The main effect of the exposure was a shift in the response to light toward a more positive phototaxis, similar to that observed in nonexposed C. finmarchicus with low lipid reserves. The observed change in phototactic behavior observed in these studies suggests that the depth distribution of this species could be altered following an oil spill. Thus, further research is warranted to determine the possible interactive effects of light and oil spill exposures on Calanus population dynamics under field conditions.

An exploratory evaluation of tyrosine hydroxylase inhibition in planaria as a model for parkinsonism

Planaria are the simplest organisms with bilateral symmetry and a central nervous system (CNS) with cephalization; therefore, they could be useful as model organisms to investigate mechanistic aspects of parkinsonism and to screen potential therapeutic agents. Taking advantage of the organism’s anti-tropism towards light, we measured a significantly reduced locomotor velocity in planaria after exposure to 3-iodo-l-tyrosine, an inhibitor of tyrosine hydroxylase that is an enzyme catalyzing the first and rate-limiting step in the biosynthesis of catecholamines. A simple semi-automatic assay using videotaped experiments and subsequent evaluation by tracking software was also implemented to increase throughput. The dopaminergic regulation of locomotor velocity was confirmed by bromocriptine, a drug whose mechanisms of action to treat Parkinson’s disease is believed to be through the stimulation of nerves that control movement.

Diet quality mediates activity patterns in adult Queensland fruit fly (Bactrocera tryoni)

Studies linking resource acquisition and trait expression have traditionally treated nutritional resources as a single currency, but recent research has shown that trait expression can depend as much on diet quality (nutrient composition) as on diet quantity (calories). Here, we investigate the role of nutrient composition and diet concentration on activity levels of adult Queensland fruit flies (Bactrocera tryoni Froggatt: Tephritidae). Male and female flies were fed diets that varied in the proportion of protein and carbohydrate as well as total amounts of protein and carbohydrate. Daily activity levels were then quantified using locomotor activity monitors during both light and dark phases. During the light phase, both sexes increased the proportion of time spent active and their rate of activity as diets became more carbohydrate-rich and concentrated. In contrast, during the dark phase, nutrient composition and concentration had no effect on the proportion of time spent active for either sex, although when active during the dark phase, activity rates were higher for flies fed more carbohydrate-rich and concentrated diets. Overall, nutritional composition of the diet affected activity levels to a greater extent than the total energetic content of the diet.

Endocrine (plasma cortisol and glucose) and behavioral (locomotor and self-feeding activity) circadian rhythms in Senegalese sole (Solea senegalensis Kaup 1858) exposed to light/dark cycles or constant light

The existence of daily rhythms under light/dark (LD) cycles in plasma cortisol, blood glucose and locomotor and self-feeding activities, as well as their persistence (circadian nature) under constant light (LL), was investigated in Senegalese sole (Solea senegalensis). For the cortisol and glucose rhythms study, 48 soles were equally distributed in 8 tanks and exposed to a 12:12 LD cycle and natural water temperature (experiment 1). After an acclimation period, blood was sampled every 3 h until a 24-h cycle was completed. Blood glucose levels were measured immediately after sampling, while plasma cortisol was measured later by ELISA. In experiment 2, the fish were exposed to LL for 11 days, and after this period, the same sampling procedure was repeated. For the study of locomotor and self-feeding rhythms (experiment 3), two groups of sole were used: one exposed to LD and the other to LL. Each group was distributed within 3 tanks equipped with infrared photocells for the record of locomotor activity, and self-feeders for feeding behavior characterization. The results revealed a marked oscillation in cortisol concentrations during the daily cycle under LD, with a peak (35.65 ± 3.14 ng/ml) in the afternoon (15:00 h) and very low levels during the night (5.30 ± 1.09 ng/ml). This cortisol rhythm persisted under LL conditions, with lower values (mean cortisol concentration = 7.12 ± 1.11 ng/ml) and with the peak shifted by 3 h. Both rhythms were confirmed by COSINOR analysis (p < 0.05). The synchronizing role of temperature and feeding schedule, in addition to light, is also discussed. Diel rhythms of glucose were not evident in LD or LL. As to locomotor and self-feeding activity, a very marked rhythm was observed under LD, with higher activity observed during the night, with acrophases located at 2:14 and 3:37 h, respectively. The statistical significance of daily rhythms was confirmed by COSINOR analysis. Under LL, both feeding and locomotor rhythms persisted, with an endogenous period (τ) around 22.5 h. In short, our findings described for the first time the existence of circadian cortisol and behavioral circadian rhythms in flat fish. Such results revealed the importance of taking into account the time of day when assessing stress responses and evaluating physiological indicators of stress in fish.

Swimming behaviour of the multicellular magnetotactic prokaryote 'Candidatus Magnetoglobus multicellularis' under applied magnetic fields and ultraviolet light

Magnetotactic bacteria move by rotating their flagella and concomitantly are aligned to magnetic fields because they present magnetosomes, which are intracellular organelles composed by membrane-bound magnetic crystals. This results in magnetotaxis, which is swimming along magnetic field lines. Magnetotactic bacteria are morphologically diverse, including cocci, rods, spirilla and multicellular forms known as magnetotactic multicellular prokaryotes (MMPs). 'Candidatus Magnetoglobus multicellularis' is presently the best known MMP. Here we describe the helical trajectories performed by these microorganisms as they swim forward, as well as their response to UV light. We measured the radius of the trajectory, time period and translational velocity (velocity along the helix axis), which enabled the calculation of other trajectory parameters such as pitch, tangential velocity (velocity along the helix path), angular frequency, and theta angle (the angle between the helix path and the helix axis). The data revealed that 'Ca. M. multicellularis' swims along elongated helical trajectories with diameters approaching the diameter of the microorganism. In addition, we observed that 'Ca. M. multicellularis' responds to UV laser pulses by swimming backwards, returning to forward swimming several seconds after the UV laser pulse. UV light from a fluorescence microscope showed a similar effect. Thus, phototaxis is used in addition to magnetotaxis in this microorganism.

The Drosophila gene RanBPM functions in the mushroom body to regulate larval behavior

BACKGROUND

In vertebrates, Ran-Binding Protein in the Microtubule Organizing Center (RanBPM) appears to function as a scaffolding protein in a variety of signal transduction pathways. In Drosophila, RanBPM is implicated in the regulation of germ line stem cell (GSC) niche organization in the ovary. Here, we addressed the role of RanBPM in nervous system function in the context of Drosophila larval behavior.

METHODOLOGY/PRINCIPAL FINDINGS

We report that in Drosophila, RanBPM is required for larval feeding, light-induced changes in locomotion, and viability. RanBPM is highly expressed in the Kenyon cells of the larval mushroom body (MB), a structure well studied for its role in associative learning in Drosophila and other insects. RanBPM mutants do not display major disruption in nervous system morphology besides reduced proliferation. Expression of the RanBPM gene in the Kenyon cells is sufficient to rescue all behavioral phenotypes. Through genetic epistasis experiments, we demonstrate that RanBPM participates with the Drosophila orthologue of the Fragile X Mental Retardation Protein (FMRP) in the development of neuromuscular junction (NMJ).

CONCLUSIONS/SIGNIFICANCE

We demonstrate that the RanBPM gene functions in the MB neurons for larval behavior. Our results suggest a role for this gene in an FMRP-dependent process. Taken together our findings point to a novel role for the MB in larval behavior.

Radiation biology of Caenorhabditis elegans: germ cell response, aging and behavior

The study of radiation effect in Caenorhabditis (C.) elegans has been carried out over three decades and now allow for understanding at the molecular, cellular and individual levels. This review describes the current knowledge of the biological effects of ionizing irradiation with a scope of the germ line, aging and behavior. In germ cells, ionizing radiation induces apoptosis, cell cycle arrest and DNA repair. Lots of molecules involved in these responses and functions have been identified in C. elegans, which are highly conserved throughout eukaryotes. Radiosensitivity and the effect of heavy-ion microbeam irradiation on germ cells with relationship between initiation of meiotic recombination and DNA lesions are discussed. In addition to DNA damage, ionizing radiation produces free radicals, and the free radical theory is the most popular aging theory. A first signal transduction pathway of aging has been discovered in C. elegans, and radiation-induced metabolic oxidative stress is recently noted for an inducible factor of hormetic response and genetic instability. The hormetic response in C. elegans exposed to oxidative stress is discussed with genetic pathways of aging. Moreover, C. elegans is well known as a model organism for behavior. The recent work reported the radiation effects via specific neurons on learning behavior, and radiation and hydrogen peroxide affect the locomotory rate similarly. These findings are discussed in relation to the evidence obtained with other organisms. Altogether, C. elegans may be a good "in vivo" model system in the field of radiation biology.

Electrotaxis of Caenorhabditis elegans in a microfluidic environment

The nematode (worm) Caenorhabditis elegans is one of the most widely studied organisms for biomedical research. Currently, C. elegans assays are performed either on petri dishes, 96-well plates or using pneumatically controlled microfluidic devices. In this work, we demonstrate that the electric field can be used as a powerful stimulus to control movement of worms in a microfluidic environment. We found that this response (termed electrotaxis) is directional, fully penetrant and highly sensitive. The characterization of electrotaxis revealed that it is mediated by neuronal activity that varies with the age and size of animals. Although the speed of swimming is unaffected by changes in the electric field strength and direction, our results show that each developmental stage responds to a specific range of electric field with a specific speed. Finally, we provide evidence that the exposure to the electric field has no discernible effect on the ability of animals to survive and reproduce. Our method has potential in precisely controlling, directing, and transporting worms in an efficient and automated manner. This opens up significant possibilities for high-throughput screening of C. elegans for drug discovery and other applications.

Optogenetic dissection of a behavioural module in the vertebrate spinal cord

Locomotion relies on neural networks called central pattern generators (CPGs) that generate periodic motor commands for rhythmic movements. In vertebrates, the excitatory synaptic drive for inducing the spinal CPG can originate from either supraspinal glutamatergic inputs or from within the spinal cord. Here we identify a spinal input to the CPG that drives spontaneous locomotion using a combination of intersectional gene expression and optogenetics in zebrafish larvae. The photo-stimulation of one specific cell type was sufficient to induce a symmetrical tail beating sequence that mimics spontaneous slow forward swimming. This neuron is the Kolmer-Agduhr cell, which extends cilia into the central cerebrospinal-fluid-containing canal of the spinal cord and has an ipsilateral ascending axon that terminates in a series of consecutive segments. Genetically silencing Kolmer-Agduhr cells reduced the frequency of spontaneous free swimming, indicating that activity of Kolmer-Agduhr cells provides necessary tone for spontaneous forward swimming. Kolmer-Agduhr cells have been known for over 75 years, but their function has been mysterious. Our results reveal that during early development in zebrafish these cells provide a positive drive to the spinal CPG for spontaneous locomotion.

Effects of ionizing radiation on locomotory behavior and mechanosensation in Caenorhabditis elegans

Locomotory behavior (motility) and mechanosensation are of vital importance in animals. We examined the effects of ionizing radiation (IR) on locomotory behavior and mechanosensation using a model organism, the nematode Caenorhabditis elegans. Bacterial mechanosensation in C. elegans induces the dopamine-mediated slowing of locomotion in the presence of bacteria (food), known as the basal slowing response. We previously reported an IR-induced reduction of locomotory rate in the absence of food. In the present study, we observed a similar IR-induced reduction of locomotory rate in the cat-2 mutant, which is defective in bacterial mechanosensation. The dose response pattern of the locomotory rate in the presence of food was relatively flat in wild-type animals, but not in cat-2 mutants. This suggests that the dopamine system, which is related to bacterial mechanosensation in C. elegans, might have a dominant effect on locomotory rate in the presence of food, which masks the effects of other stimuli. Moreover, we found that the behavioral responses of hydrogen peroxide-exposed wild-type animals are similar to those of IR-exposed animals. Our findings suggest that the IR-induced reduction of locomotory rate in the absence of food is mediated by a different pathway from that for bacterial mechanosensation, at least partially through IR-produced hydrogen peroxide.

Prokaryotic phototaxis

Microorganisms have various mechanisms at their disposal to react to (changes in) their ambient light climate (i.e., intensity, color, direction, and degree of polarization). Of these, one of the best studied mechanisms is the process of phototaxis. This process can be described as a behavioral migration-response of an organism toward a change in illumination regime. In this chapter we discuss three of these migration responses, based on swimming, swarming, and twitching motility, respectively. Swimming motility has been studied using a wide range of techniques, usually microscopy based. We present a detailed description of the assays used to study phototaxis in liquid cultures of the phototrophic organisms Halobacterium salinarum, Halorhodospira halophila, and Rhodobacter sphaeroides and briefly describe the molecular basis of these responses. Swarming and twitching motility are processes taking place at the interface between a solid phase and a liquid or gas phase. Although assays to study these processes are relatively straightforward, they are accompanied by technical complications, which we describe. Furthermore, we discuss the molecular processes underlying these forms of motility in Rhodocista centenaria and Synechocystis PCC6803. Recently, it has become clear that also chemotrophic organisms contain photoreceptor proteins that allow them to respond to their ambient light climate. Surprisingly, light-modulated motility responses can also be observed in the chemotrophic organisms Escherichia coli and Acinetobacter calcoaceticus. In the light-modulated surface migration not only "che-like" signal transduction reactions may play a role, but in addition processes as modulation of gene expression and even intermediary metabolism.

Dictyostelium slug phototaxis

Dictyostelium slugs are able to respond to environmental stimuli in an extremely sensitive and efficient way. This enables a slug to migrate to more favourable locations for formation of fruiting bodies and dispersal of spores. Phototaxis is a readily assayed phenotype and reflects the interactions of environmental stimuli with morphogenetic signalling systems controlling the movement of the slug. The methods for assaying phototaxis are described here. Qualitative phototaxis tests are described and can be used for rapid screening of potential mutants or effects of pharmacological agents. These tests are simple to conduct yet care must be taken in order to avoid the effects of high cell density which can be misleading when interpreting results. Quantitative phototaxis tests can be performed with known cell densities of amoebae which ensures that any effects seen are caused by the mutation or pharmacological agent and not simply due to differences in cell densities.

Postural performance in decerebrated rabbit

It is known that animals decerebrated at the premammillary level are capable of standing and walking without losing balance, in contrast to postmammillary ones which do not exhibit such behavior. The main goals of the present study were, first, to characterize the postural performance in premammillary rabbits, and, second, to activate the postural system in postmammillary ones by brainstem stimulation. For evaluation of postural capacity of decerebrated rabbits, motor and EMG responses to lateral tilts of the supporting platform and to lateral pushes were recorded before and after decerebration. In addition, the righting behavior (i.e., standing up from the lying position) was video recorded. We found that, in premammillary rabbits, responses to lateral tilts and pushes were similar to those observed in intact ones, but the magnitude of responses was reduced. During righting, premammillary rabbits assumed the normal position slower than intact ones. To activate the postural system in postmammillary rabbits, we stimulated electrically two brainstem structures, the mesencephalic locomotor region (MLR) and the ventral tegmental field (VTF). The MLR stimulation (prior to elicitation of locomotion) and the VTF stimulation caused an increase of the tone of hindlimb extensors, and enhanced their responses to lateral tilts and to pushes. These results indicate that the basic mechanisms for maintenance of body posture and equilibrium during standing are present in decerebrated animals. They are active in the premammillary rabbits but need to be activated in the postmammillary ones.

Locomotion-learning behavior relationship in Caenorhabditis elegans following gamma-ray irradiation

Learning impairment following ionizing radiation (IR) exposure is an important potential risk in manned space missions. We previously reported the modulatory effects of IR on salt chemotaxis learning in Caenorhabditis elegans. However, little is known about the effects of IR on the functional relationship in the nervous system. In the present study, we investigated the effects of gamma-ray exposure on the relationship between locomotion and salt chemotaxis learning behavior. We found that effects of pre-learning irradiation on locomotion were significantly correlated with the salt chemotaxis learning performance, whereas locomotion was not directly related to chemotaxis to NaCl. On the other hand, locomotion was positively correlated with salt chemotaxis of animals which were irradiated during learning, and the correlation disappeared with increasing doses. These results suggest an indirect relationship between locomotion and salt chemotaxis learning in C. elegans, and that IR inhibits the innate relationship between locomotion and chemotaxis, which is related to salt chemotaxis learning conditioning of C. elegans.

Dose dependence of the 5-HT agonist quipazine in facilitating spinal stepping in the rat with epidural stimulation

Epidural electrical stimulation (ES) at spinal cord segment L2 can produce coordinated step-like movements in completely spinalized adult rats [R.M. Ichiyama, Y.P. Gerasimenko, H. Zhong, R.R. Roy, V.R. Edgerton, Hindlimb stepping movements in complete spinal rats induced by epidural spinal cord stimulation, Neurosci. Lett. 383 (2005) 339-344]. Plantar placement of the paws, however, was rarely observed. Here, we sought to determine the dose dependence of a 5-HT agonist (quipazine) on stepping kinematics when administered in combination with ES. Six adult female Sprague-Dawley rats received a complete mid-thoracic spinal cord transection and were implanted with epidural electrodes at the L2 spinal cord level. Quipazine (i.p.) was tested at doses of 0.1, 0.2, 0.3, 0.4, and 0.5 mg/kg. Rats were placed in a body weight support system, allowing them to walk bipedally on a moving treadmill belt (7 cm/s). 3D step kinematics analysis revealed that coordinated alternating bilateral stepping was induced by L2 stimulation (50 Hz) alone and by quipazine alone. Furthermore, the combination treatment produced significantly greater numbers of plantar steps and improved quality of stepping compared to either intervention alone. Both number and quality of stepping peaked at the intermediate dose of 0.3-0.4 mg/kg. The results indicate that quipazine and ES can have complementary effects on spinal circuits and that quipazine dosage is an important factor in differentially modulating these circuitries to improve the quality of the bipedal stepping on a treadmill belt.

Epidural spinal cord stimulation plus quipazine administration enable stepping in complete spinal adult rats

We hypothesized that epidural spinal cord stimulation (ES) and quipazine (a serotonergic agonist) modulates the excitability of flexor and extensor related intraspinal neural networks in qualitatively unique, but complementary, ways to facilitate locomotion in spinal cord-injured rats. To test this hypothesis, we stimulated (40 Hz) the S(1) spinal segment before and after quipazine administration (0.3 mg/kg, ip) in bipedally step-trained and nontrained, adult, complete spinal (mid-thoracic) rats. The stepping pattern of these rats was compared with control rats. At the stimulation levels used, stepping was elicited only when the hindlimbs were placed on a moving treadmill. In nontrained rats, the stepping induced by ES and quipazine administration was non-weight bearing, and the cycle period was shorter than in controls. In contrast, the stepping induced by ES and quipazine in step-trained rats was highly coordinated with clear plantar foot placement and partial weight bearing. The effect of ES and quipazine on EMG burst amplitude and duration was greater in flexor than extensor motor pools. Using fast Fourier transformation analysis of EMG bursts during ES, we observed one dominant peak at 40 Hz in the medial gastrocnemius (ankle extensor), whereas there was less of dominant spectral peak in the tibialis anterior (ankle flexor). We suggest that these frequency distributions reflect amplitude modulation of predominantly monosynaptic potentials in the extensor and predominantly polysynaptic pathways in the flexor muscle. Quipazine potentiated the amplitude of these responses. The data suggest that there are fundamental differences in the circuitry that generates flexion and extension during locomotion.

Epidural stimulation: comparison of the spinal circuits that generate and control locomotion in rats, cats and humans

Although epidural stimulation is a technique that has been used for a number of years to treat individuals with a spinal cord injury, the intended outcome has been to suppress plasticity and pain. Over the last decade considerable progress has been made in realizing the potential of epidural stimulation to facilitate posture and locomotion in subjects with severe spinal cord injury who lack the ability to stand or to step. This progress has resulted primarily from experiments with mice, rats and cats having a complete spinal cord transection at a mid-thoracic level and in humans with a complete spinal cord injury. This review describes some of these experiments performed after the complete elimination of supraspinal input that demonstrates that the circuitry necessary to control remarkably normal locomotion appears to reside within the lumbosacral region of the spinal cord. These experiments, however, also demonstrate the essential role of processing proprioceptive information associated with weight-bearing stepping or standing by the spinal circuitry. For example, relatively simple tonic signals provided to the dorsum of the spinal cord epidurally can result in complex and highly adaptive locomotor patterns. Experiments emphasizing a significant complementary effect of epidural stimulation when combined with pharmacological facilitation, e.g., serotonergic agonists, and/or chronic step training also are described. Finally, a major point emphasized in this review is the striking similarity of the lumbosacral circuitry controlling locomotion in the rat and in the human.

CART peptide 55-102 microinjected into the nucleus accumbens inhibits the expression of behavioral sensitization by amphetamine

CART peptide has been shown to regulate the actions of psychomotor stimulants. Here we have further investigated the role of the biologically active CART 55-102 peptide in the nucleus accumbens (NAcc) in the expression of behavioral sensitization by amphetamine (AMPH). Rats were pre-exposed 5 times to either saline or AMPH (1 mg/kg, i.p.). After 2 weeks of withdrawal, rats were microinjected into the NAcc with saline or CART 55-102 (1.0, or 2.5 microg/0.5 microl/side) followed by AMPH challenge (1 mg/kg, i.p.). The enhanced increase of locomotion and rearing produced by repeated AMPH pre-exposures was dose-dependently inhibited by microinjection into the NAcc of CART 55-102 peptide. These results indicate that CART 55-102 peptide in the NAcc can play a compensatory inhibitory role in the expression of behavioral sensitization by AMPH and further suggest that CART peptide may be a useful target to control the drug addiction by psychomotor stimulants.

Intraspinal Stimulation Caudal to Spinal Cord Transections in Rats. Testing the Propriospinal Hypothesis

Many laboratories have reported the successful regeneration of neurons across damaged portions of the spinal cord. Associated improvements in hindlimb locomotor movements have been attributed to the formation of functional neuronal connections with the locomotor central pattern generator (CPG). However, regenerating axons generally extend no more than 10 mm caudal to the lesion sites, terminating about 20 mm short of the lumbar segments thought to contain the CPG. It has therefore tacitly been assumed that the locomotor improvements arose from activation of propriospinal neurons relaying excitation to the CPG. Here we report a test of this assumption, which we call the propriospinal hypothesis. Intraspinal microstimulation (ISMS) was used to activate the putative propriospinal relay neurons. Approximately 2–3 wk after complete spinal cord transection at T8–T9 in rats, an array of six Pt–Ir microwires was chronically implanted in the intermediate and ventral gray matter of T10–T12 segments. ISMS pulse trains with amplitudes of 0.8–0.9 times threshold for activating axial muscles were delivered during open-field locomotor tests (BBB). ISMS significantly increased BBB scores over control tests, but did not produce limb coordination and weight bearing sufficient for locomotion. These results support the main assumption of the propriospinal hypothesis: that neuronal activity elicited in thoracic spinal segments caudal to a complete spinal cord transection may propagate caudally and activate the locomotor CPG.

Short-Term Adaptation and Temporal Processing in the Cryophilic Response ofCaenorhabditis elegans

When navigating spatial thermal gradients, the nematode C. elegans migrates toward colder temperatures until it reaches its previous cultivation temperature, exhibiting cryophilic movement. The strategy for effecting cryophilic movement is the biased random walk: C. elegans extends (shortens) periods of forward movement that are directed down (up) spatial thermal gradients by modulating the probability of reorientation. Here, we analyze the temporal sensory processor that enables cryophilic movement by quantifying the movements of individual worms subjected to defined temperature waveforms. We show that step increases in temperature as small as 0.05°C lead to transient increases in the probability of reorientation followed by gradual adaptation to the baseline level; temperature downsteps leads to similar but inverted responses. Short-term adaptation is a general property of sensory systems, allowing organisms to maintain sensitivity to sensory variations over broad operating ranges. During cryophilic movement C. elegans also uses the temporal dynamics of its adaptive response to compute the time derivative of gradual temperature variations with exquisite sensitivity. On the basis of the time derivative, the worm determines how it is oriented in spatial thermal gradients during each period of forward movement. We show that the operating range of the cryophilic response extends to lower temperatures in ttx-3 mutants, which affects the development of the AIY interneurons. We show that the temporal sensory processor for the cryophilic response is affected by mutation in the EAT-4 glutamate vesicular transporter. Regulating the operating range of the cryophilic response and executing the cryophilic response may have separate neural mechanisms.

Fluence Rate or Cumulative Dose? Vulnerability of Larval Northern Pike (Esox lucius) to Ultraviolet Radiation

Newly hatched larvae of northern pike were exposed in the laboratory to four fluence rates of ultraviolet radiation (UVR; 290-400 nm) over three different time periods, resulting in total doses ranging from 3.0 +/- 0.2 to 63.0 +/- 4.4 kJ.m(-2). Mortality and behavior of the larvae were followed for 8-12 days, and growth measured at the end of the experiment. Also, the principle of reciprocity-that the UVR-induced mortality depends on the cumulative dose, independent of fluence rate-was tested. Fluence rates higher than 1480 +/- 150 mW.m(-2) caused mortality and growth retardation. The highest fluence rate (3040 +/- 210 mW.m(-2)) caused 100% mortality in 5 days. All fluence rates caused behavioral disorders, which led to death at fluence rates higher than 1480 mW.m(-2). Reciprocity failure occurred with the lowest and highest dose (550 +/- 45 and 3040 +/- 210 mW.m(-2), respectively). The results show that fluence rate is of primary importance when assessing the UVR-related risk.

Kinematic analysis of Drosophila larval locomotion in response to intermittent light pulses

We report a quantitative analysis of the modulation of locomotion by light in the Drosophila larva. The photobehavior of wild type larvae and of larvae carrying mutations altering various aspects of locomotion was evaluated in an assay that exposes individual animals to intermittent pulses of dark and light (ON/OFF assay). The application of the Dynamic Image Analysis System for the analysis of larval movement in the ON/OFF assay allowed a detailed description of the behavioral repertoire underlying the modulation of larval motion by light. We established that the larval response to light is characterized by decreased frequency of peristaltic contractions in addition to increased direction change and pausing. Moreover, using various mutant strains we show that this approach allows the detection of a response to light in mutant larvae whose locomotion is severely reduced and uncoordinated, mutants that would otherwise have been considered non-responders in this assay.

A hemicord locomotor network of excitatory interneurons: a simulation study

Locomotor burst generation is simulated using a full-scale network model of the unilateral excitatory interneuronal population. Earlier small-scale models predicted that a population of excitatory neurons would be sufficient to produce burst activity, and this has recently been experimentally confirmed. Here we simulate the hemicord activity induced under various experimental conditions, including pharmacological activation by NMDA and AMPA as well as electrical stimulation. The model network comprises a realistic number of cells and synaptic connectivity patterns. Using similar distributions of cellular and synaptic parameters, as have been estimated experimentally, a large variation in dynamic characteristics like firing rates, burst, and cycle durations were seen in single cells. On the network level an overall rhythm was generated because the synaptic interactions cause partial synchronization within the population. This network rhythm not only emerged despite the distributed cellular parameters but relied on this variability, in particular, in reproducing variations of the activity during the cycle and showing recruitment in interneuronal populations. A slow rhythm (0.4-2 Hz) can be induced by tonic activation of NMDA-sensitive channels, which are voltage dependent and generate depolarizing plateaus. The rhythm emerges through a synchronization of bursts of the individual neurons. A fast rhythm (4-12 Hz), induced by AMPA, relies on spike synchronization within the population, and each burst is composed of single spikes produced by different neurons. The dynamic range of the fast rhythm is limited by the ability of the network to synchronize oscillations and depends on the strength of synaptic connections and the duration of the slow after hyperpolarization. The model network also produces prolonged bouts of rhythmic activity in response to brief electrical activations, as seen experimentally. The mutual excitation can sustain long-lasting activity for a realistic set of synaptic parameters. The bout duration depends on the strength of excitatory synaptic connections, the level of persistent depolarization, and the influx of Ca(2+) ions and activation of Ca(2+)-dependent K(+) current.

Physiologically based controller for generating overground locomotion using functional electrical stimulation

The physiological control of stepping is governed both by signals descending from supraspinal systems and by circuitry residing within the lumbosacral spinal cord. The goal of this study was to evaluate the capacity of physiologically based controllers to restore functional overground locomotion after neurological damage, such as spinal cord injury when used in conjunction with functional electrical stimulation. For this purpose we implemented and tested two controllers: 1) an intrinsically timed system that generated a predetermined rhythmic output and 2) a sensory-based system that used feedback signals to make appropriate transitions between the unloaded (flexion) and loaded (extension) phases of the gait cycle. A third controller, a combination of the intrinsically timed and sensory-driven controllers, was implemented and two sessions were conducted to demonstrate the functional advantages of this approach. The controllers were tested in anesthetized cats, implanted with intramuscular electrodes in six major extensor and flexor muscles of the hindlimbs. The cats were partially supported on a sliding trolley that was propelled by the hindlimbs along a 2.5-m instrumented walkway. Ground reaction forces and limb positions were measured by force plates in the walkway and by accelerometers secured to the legs of the cat, respectively. The controllers were used to generate patterns of stimulation that would elicit alternating flexor (swing) and extensor (stance) movements in the hindlimbs. Using either the intrinsically timed or sensory-driven controllers, the cats were able to travel a distance of 2.5 m, taking five to 12 steps. Functional stepping sequences were more easily achieved using the intrinsically timed controller as the result of a lower sensitivity to the selection of initial stimulation parameters. However, unlike the sensory-driven controller, the intrinsically timed controller was unable to adjust to overcome walkway resistance and muscle fatigue. Neither system was consistently able to ensure load-bearing stepping. Therefore we propose the use of a "combined controller" that relies heavily on intrinsic timing but that can be reset based on sensory signals. A combined controller such as this one may provide the best solution for restoring robust overground locomotion after spinal cord injury.

Characteristics and mechanisms of locomotion induced by intraspinal microstimulation and dorsal root stimulation in spinal cats

Intraspinal microstimulation (ISMS) through a single microelectrode can induce locomotion in cats spinalized at T(13) 1 wk before (untrained) or after 3-5 wk of treadmill training. Here we study the optimal parameters of ISMS and the characteristics of locomotion evoked. ISMS was applied in the dorsal region of segments L(3)-S(1) at different lateralities (midline to 2.5 mm) and after an intravenous injection of clonidine (noradrenergic agonist). Kinematics and electromyographic recordings were used to characterize locomotion. ISMS could induce a bilateral locomotor pattern similar to that obtained with perineal stimulation, and the characteristics of locomotion varied according to the spinal segment stimulated. Mechanisms by which ISMS could evoke locomotion were then investigated by stimulating, inactivating, or lesioning different spinal structures. Dorsal root stimulation (DRS), just like ISMS, could evoke a variety of ipsi- and bilateral nonlocomotor movements as well as locomotor responses. This suggests that sensory afferent pathways are involved in the production of locomotion by ISMS. Microinjections of yohimbine (noradrenergic antagonist) in L(3) and L(4) segments or a complete second spinal lesion at L(3)-L(4) abolished all locomotor activity evoked by ISMS applied at more caudal segments. Progressive dorsoventral spinal lesions at L(3) or L(4) and restricted ventral lesions at L(4) further suggest that the integrity of the ventral or ventrolateral funiculi as well as the L(3)-L(4) segments are critical for the induction of locomotion by ISMS at L(5) to S(1) or by DRS at these caudal segments.

Influence of ultraviolet radiation on selected physiological responses of earthworms

The purpose of this study was to investigate the adverse effects of ultraviolet (UV) radiation on earthworms. Earthworms that crawl out of the soil may die within a few hours after sunrise. This study shows that UV exposure can be lethal. In general, UV-B had a stronger damaging effect than UV-A. Different species of earthworms had different tolerances to UV exposure. In this study, Pontoscolex corethrurus showed the highest tolerance of the three tested species to UV radiation, while Amynthas graciliswas the most sensitive. UV radiation induced both acute and chronic responses. The acute response, which occurred immediately on or after UV exposure, was characterized by the appearance of abnormally strong muscle contractions,including S-shaped movements and jumping behavior, possibly caused by bad coordination between the circular and longitudinal muscles. The chronic response included damage to the skin and muscle cells, which resulted in a high mortality rate. Oxygen consumption by A. gracilis was significantly decreased after exposure to UV-A or UV-B. Since the circulation in earthworms is mediated by muscle contraction and the skin is the main organ of respiration, it is reasonable to expect that abnormal muscle contraction and a damaged epithelium could cause suffocation. Because of their sensitive responses, we propose that some earthworms, such as A. gracilis,could serve as a new model for studying UV-induced photodamage.