Effects Of Brief Exposure Research Articles

Fitting the mind to the world: face adaptation and attractiveness aftereffects.

Average faces are attractive, but what is average depends on experience. We examined the effect of brief exposure to consistent facial distortions on what looks normal (average) and what looks attractive. Adaptation to a consistent distortion shifted what looked most normal, and what looked most attractive, toward that distortion. These normality and attractiveness aftereffects occurred when the adapting and test faces differed in orientation by 90 degrees (+45 degrees vs. -45 degrees ), suggesting adaptation of high-level neurons whose coding is not strictly retino- topic. Our results suggest that perceptual adaptation can rapidly recalibrate people's preferences to fit the faces they see. The results also suggest that average faces are attractive because of their central location in a distribution of faces (i.e., prototypicality), rather than because of any intrinsic appeal of particular physical characteristics. Recalibration of preferences may have important consequences, given the powerful effects of perceived attractiveness on person perception, mate choice, social interactions, and social outcomes for individuals.

Increased anxiety and "depressive" symptoms months after MDMA ("ecstasy") in rats: drug-induced hyperthermia does not predict long-term outcomes.

There is some uncertainty whether the acute hyperthermia caused by MDMA (ecstasy) plays a significant role in determining the long-term neurotoxic effects on brain 5-HT systems and associated changes in mood and behaviour. The present study assessed whether long-term behavioural and cognitive changes seen in MDMA-treated rats are affected by hyperthermia at the time of drug administration. Male Wistar rats were treated with MDMA (4x5 mg/kg i.p. over 4 h on 2 consecutive days) or vehicle at either a high ambient temperature (28 degrees C) or a low ambient temperature (16 degrees C). Eight to 18 weeks later, rats were tested in behavioural measures of anxiety (social interaction and emergence tests), a test of cognition (object recognition test) and the forced swim test of depression. At the conclusion of behavioural testing the rats were killed and their brains analysed using HPLC. MDMA treatment caused a clear and consistent hyperthermia at 28 degrees C and hypothermia at 16 degrees C. Months later, rats pre-treated with MDMA at either 16 or 28 degrees C displayed increased anxiety in the social interaction and emergence tests and reduced escape attempts and increased immobility in the forced swim test. MDMA pre-treatment was also associated with poorer memory on the object recognition test, but only in rats given the drug at 28 degrees C. Rats pre-treated with MDMA showed loss of 5-HT in the hippocampus, striatum, amygdala and cortex, regardless of body temperature at the time of dosing. However, 5-HIAA loss in the amygdala and hippocampus was greater in rats pre-treated at 28 degrees C. Dopamine in the striatum was also depleted in rats given MDMA. These results indicate that hyperthermia at the time of dosing with MDMA is not necessary to produce subsequent 5-HT depletion and anxiety in rats. They also extend previous findings of long-term effects of brief exposure to MDMA in rats to include apparent "depressive" symptoms in the forced swim model.

Brief exposure to high-dose transforming growth factor-beta1 enhances periosteal chondrogenesis in vitro: a preliminary report.

Articular cartilage has limited potential for repair. There have been various attempts aimed at improving the repair process in articular cartilage. Transforming growth factor-beta1 (TGF-beta1) has a stimulatory effect on chondrogenesis in periosteal explants. The purpose of the present study was to determine the effect of brief exposures (i.e., thirty and sixty minutes) of high concentrations of TGF-beta1 on periosteal chondrogenesis. Five hundred and seventy-three periosteal explants were harvested from forty-six two-month-old male New Zealand White rabbits. Explants were exposed to 50 or 100 ng/mL of TGF-beta1 for thirty or sixty minutes. The amount of cartilage formed was then determined with use of a standardized six-week agarose culture assay. There was a significant increase in the amount of cartilage formation (p < 0.01), Type-II collagen content (p < 0.05), and sulfate incorporation (p < 0.0001) in explants treated with TGF-beta1. Maximal stimulation occurred following exposure to 100 ng/mL of TGF-beta1 for thirty minutes. There was also an increase in chondrocyte proliferation as measured by [ (3) H-] thymidine incorporation on day 5 of culture (p < 0.049). The findings of this study indicate that exposure to TGF-beta1 has a stimulatory effect on periosteal chondrogenesis. This stimulatory effect is observed even with a very brief exposure time of thirty minutes. A possible clinical application of these findings is exposure of periosteal grafts that are currently utilized clinically to resurface articular defects to TGF-beta1 during the short time between graft procurement and implantation into the joint. This may obviate the need for intra-articular administration of TGF-beta1 and may enhance the ultimate graft incorporation and quality of cartilage repair.

Priming of Macrophages with Lipopolysaccharide Potentiates P2X7-mediated Cell Death via a Caspase-1-dependent Mechanism, Independently of Cytokine Production

ATP stimulation of cell surface P2X7 receptors results in cytolysis and cell death of macrophages. Activation of this receptor in bacterial lipopolysaccharide (LPS)-activated macrophages or monocytes also stimulates processing and release of the cytokine interleukin-1beta(IL-1beta) through activation of caspase-1. The cytokine interleukin 18 (IL-18) is also cleaved by caspase-1 and shares pro-inflammatory characteristics with IL-1beta. The objective of the present study was to test the hypothesis that IL-1beta, IL-18, and/or caspase-1 activation contribute directly to macrophage cell death induced by LPS and ATP. Macrophages were cultured from normal mice or those in which genes for the P2X7 receptor, IL-1beta, IL-1alpha, IL-18, or caspase-1 had been deleted. Our data confirm the importance of the P2X7 receptor in ATP-stimulated cell death and IL-1beta release from LPS-primed macrophages. We demonstrate that prolonged stimulation with ATP leads to cell death, which is partly dependent on LPS priming and caspase-1, but independent of cytokine processing and release. We also provide evidence that LPS priming of macrophages makes them highly susceptible to the toxic effects of brief exposure to ATP, which leads to rapid cell death by a mechanism that is dependent on caspase-1 but, again, independent of cytokine processing and release.

Antiproliferative effect of brief exposure to cholera toxin in vascular smooth muscle cells: role of cAMP and protein kinase A

The effect of cholera toxin (CTX), an activator of the adenylate cyclase-coupled G protein alpha(s) subunit, was studied on cultured vascular smooth muscle cell (VSMC) proliferation. Continuous exposure (48 h) to CTX as well as 2-min pretreatment of VSMC with CTX led to the same level of cAMP production, inhibition of DNA synthesis, and arrest in the G1 phase without induction of necrosis or apoptosis in VSMC. Protein kinase A (PKA) activity in CTX-pretreated cells was transiently elevated by 3-fold after 3 h of incubation, whereas after 48 h it was reduced by 2-fold compared with baseline values without modulation of the expression of its catalytic alpha subunit. The PKA inhibitors H89 and KT 5720 did not protect VSMC from the antiproliferative effect of CTX. Two-dimensional electrophoresis was used to analyze the influence of CTX on protein phosphorylation. After 3 h of incubation of CTX-pretreated cells, we observed both newly-phosphorylated and dephosphorylated proteins (77 and 50 protein species, respectively). After 24 h of incubation, the number of phosphorylated proteins in CTX-treated cells was decreased to 39, whereas the number of dephosphorylated proteins was increased to 106. In conclusion, brief exposure to CTX leads to full-scale activation of cAMP signaling and evokes VSMC arrest in the G1 phase.

The impact of chlorhexidine gluconate on the relative cell surface hydrophobicity of oral Candida albicans

Adherence of Candida albicans has been implicated as the first step in the pathogenesis of oral candidosis, and its relative cell surface hydrophobicity (CSH) a contributory physical force. Chlorhexidine gluconate is by far the commonest antiseptic mouthwash prescribed in dentistry. The intra-oral concentrations of the retained chlorhexidine mouthwash fluctuate considerably due to the dilution effect of saliva and the cleansing action of the oral musculature. Hence the objective of the present study was to investigate the effect of brief exposure to sub-therapeutic concentrations of chlorhexidine gluconate on the relative CSH of C. albicans. The CSH of the isolates was assessed by a biphasic aqueous-hydrocarbon assay. A statistically significant reduction in CSH was observed following the exposure of Candida isolates to 0.005 and 0.0025% chlorhexidine gluconate. These results elucidate additional mechanisms by which chlorhexidine gluconate suppress candidal pathogenicity despite a brief period of transient exposure within the oral environment.

The impact of chlorhexidine gluconate on the relative cell surface hydrophobicity of oral Candida albicans

OBJECTIVES: Adherence of Candida albicans has been implicated as the first step in the pathogenesis of oral candidosis, and its relative cell surface hydrophobicity (CSH) a contributory physical force. Chlorhexidine gluconate is by far the commonest antiseptic mouthwash prescribed in dentistry. The intra-oral concentrations of the retained chlorhexidine mouthwash fluctuate considerably due to the dilution effect of saliva and the cleansing action of the oral musculature. Hence the objective of the present study was to investigate the effect of brief exposure to sub-therapeutic concentrations of chlorhexidine gluconate on the relative CSH of C. albicans. DESIGN: The CSH of the isolates was assessed by a biphasic aqueous-hydrocarbon assay. RESULTS: A statistically significant reduction in CSH was observed following the exposure of Candida isolates to 0.005 and 0.0025% chlorhexidine gluconate. CONCLUSIONS: These results elucidate additional mechanisms by which chlorhexidine gluconate suppress candidal pathogenicity despite a brief period of transient exposure within the oral environment.

Antiproliferative effect of brief exposure to cholera toxin in vascular smooth muscle cells: role of cAMP and protein kinase A

The effect of cholera toxin (CTX), an activator of the adenylate cyclase-coupled G protein alpha(s) subunit, was studied on cultured vascular smooth muscle cell (VSMC) proliferation. Continuous exposure (48 h) to CTX as well as 2-min pretreatment of VSMC with CTX led to the same level of cAMP production, inhibition of DNA synthesis, and arrest in the G1 phase without induction of necrosis or apoptosis in VSMC. Protein kinase A (PKA) activity in CTX-pretreated cells was transiently elevated by 3-fold after 3 h of incubation, whereas after 48 h it was reduced by 2-fold compared with baseline values without modulation of the expression of its catalytic alpha subunit. The PKA inhibitors H89 and KT 5720 did not protect VSMC from the antiproliferative effect of CTX. Two-dimensional electrophoresis was used to analyze the influence of CTX on protein phosphorylation. After 3 h of incubation of CTX-pretreated cells, we observed both newly-phosphorylated and dephosphorylated proteins (77 and 50 protein species, respectively). After 24 h of incubation, the number of phosphorylated proteins in CTX-treated cells was decreased to 39, whereas the number of dephosphorylated proteins was increased to 106. In conclusion, brief exposure to CTX leads to full-scale activation of cAMP signaling and evokes VSMC arrest in the G1 phase.

Effect of brief exposure to a potential predator on cortisol concentrations in female Columbian ground squirrels (Spermophilus columbianus)

We examined the effect of exposure to a potential predator on cortisol concentrations in captive female Columbian ground squirrels (Spermophilus columbianus) and determined if lactation mitigated this cortisol response. Lactating and nonlactating females were exposed to a dog (Canis familiaris) for 5 min once a week over a 8-week period. Blood was collected 5 min and 2.5 and 4.5 h after exposure to the dog. Females exposed to the dog had higher concentrations of total (but not free) cortisol than unexposed females only in the 5-min blood sample. Over the active season, total- and free-cortisol levels were 37-47% higher in females exposed to the dog than in unexposed females in early to mid-July when young were being weaned. The cortisol response to the dog was suppressed during lactation. Cortisol levels were, on average, 41-59% lower during lactation than during nonlactation 5 min (but not 2.5 or 4.5 h) after exposure to the dog.

Effect of brief exposure to glare on brightness perception in the scotopic-mesopic range

This paper reports a study of the effect of disability glare in the scotopic-mesopic range when there is brief exposure to glare to provide conditions similar to those encountered in night driving. Subjects compare the brightness of two uniform luminance fields that are displayed sequentially, when one of them is presented under glare conditions. The observers report which field is brighter. A forced-choice paradigm using the method of constant stimuli is used to determine the luminance corresponding to the perceptual matching luminance. Results show a non-linear relation of the glare illuminance to the matching luminance and a non-significant dependence on the luminance reference. The experimental data closely fit an equation taken from previous studies on the effect of a peripheral glare source upon the apparent brightness of an object. The relation between matching luminance and reference luminance could be an easy way to measurement the effect of glare.

Effect of brief exposure to a potential predator on cortisol concentrations in female Columbian ground squirrels (&lt;i&gt;Spermophilus columbianus&lt;/i&gt;)

Effect of brief exposure to a potential predator on cortisol concentrations in female Columbian ground squirrels (&lt;i&gt;Spermophilus columbianus&lt;/i&gt;)

Brief 95% O2 exposure effects on surfactant protein and mRNA in rat alveolar and bronchiolar epithelium.

In acute lung injury, a disturbed surfactant system may impair gas exchange. Previous evaluations of hyperoxia effects on surfactant proteins (SPs) followed exposures >1-2 days. To evaluate the effects of brief exposure to hyperoxia on the SP system, we exposed adult male rats to 95% O2 or air for 12, 36, and 60 h. SP-A, -B, and -C mRNAs were analyzed by Northern blot and semiquantitative in situ hybridization (ISH). SP-A and -B were analyzed in whole lung homogenates, lung lavage fluid, and fixed tissue by semiquantitative immunohistochemistry (IHC). All SP mRNAs were diminished at 12 h and rose to or exceeded control by 60 h as determined by Northern blot and ISH. These effects were seen mainly in the intensity of ISH signal per cell in both type II and bronchiolar epithelial (Clara) cells and to a lesser extent on numbers of positively labeled cells. SP-B declined to 50% of control in lavage at 12 h, but no changes in total lung SP-A and -B were seen. The number of SP-A positively labeled cells did not change, but SP-A label intensity measured by IHC in type II cells showed parallel results to Northern blots and ISH. The response of SP-A in Clara cells was similar. SP-B immunolabeling intensity rose in both type II and Clara cells throughout the exposure. SP-C ISH intensity fell at 12 h and was increased to two times control by 60 h of hyperoxia. Sharp declines in SP expression occurred by 12 h of 95% O2 and may affect local alveolar stability.

Postexposure effects of brief cadmium, zinc, and phenol exposures on freshwater organisms

AbstractConventional toxicity testing has relied heavily on fixed duration continuous exposure conditions. These conditions have little relevance to the exposure conditions of many environmental pollutants, particularly the highly variable and often brief exposure regimes of episodic pollution events. This research was designed to assess the effects of brief exposures using a postexposure observation period. The common freshwater organisms Ceriodaphnia dubia, Hyalella azteca, and Pimephales promelas were exposed to a range of cadmium (Cd), zinc (Zn), and/or phenol concentrations for durations ranging from 15 to 240 min. Immobility was measured for up to 7 d after the exposure period. Results showed that organisms exposed to Cd and Zn exhibited delayed effects that resulted in increasing immobility for up to 172 h after the exposure period. Ceriodaphnia dubia, H. azteca, and P. promelas exposed to Cd for as short as 30 min exhibited 100, 95, and 85% immobility, respectively, during postexposure observation. Ceriodaphnia dubia and H. azteca exposed to Zn for as short as 30 min exhibited 100 and 30% immobility, respectively, during postexposure observation. Ceriodaphnia dubia exposed to phenol exhibited recovery of mobility after the exposure period. The presence of delayed effects or organism recovery suggests that toxicity tests used to monitor brief exposures should use environmentally relevant exposure durations and postexposure observations.

Educational Research Volume 40 Number 1 Spring 1998 The effects of brief exposure and of classroom teaching on attitudes children express towards facial disfigurement in peers

Summary This report describes a controlled study of the impact of the pilot use of an education pack on primary school pupils’ attitudes to facial disfigurement. Projective materials were used to investigate their perceptions in terms of a hierarchical list of educational objectives ‐‐ awareness, knowledge, understanding, acceptance and commitment. There were significant changes in score in the control schools, as well as the project schools. All statistically significant changes, and all changes relating to disfigured children, were in the desired direction. In response to photographs showing disfigurement, children in the pilot schools consistently improved their scores by a greater margin than those in the control schools. But this difference reached statistical significance only for the Knowledge objective. There was no difference between the groups in relation to the Commitment objective. The results are discussed in terms of the impact of brief exposure and of classroom teaching. The findings have implications for decisions among different strategies of intervention that might be adopted in schools using the materials.

POSTEXPOSURE EFFECTS OF BRIEF CADMIUM, ZINC, AND PHENOL EXPOSURES ON FRESHWATER ORGANISMS

Conventional toxicity testing has relied heavily on fixed duration continuous exposure conditions. These conditions have little relevance to the exposure conditions of many environmental pollutants, particularly the highly variable and often brief exposure regimes of episodic pollution events. This research was designed to assess the effects of brief exposures using a postexposure observation period. The common freshwater organisms Ceriodaphnia dubia, Hyalella azteca, and Pimephales promelas were exposed to a range of cadmium (Cd), zinc (Zn), and/or phenol concentrations for durations ranging from 15 to 240 min. Immobility was measured for up to 7 d after the exposure period. Results showed that organisms exposed to Cd and Zn exhibited delayed effects that resulted in increasing immobility for up to 172 h after the exposure period. Ceriodaphnia dubia, H. azteca, and P. promelas exposed to Cd for as short as 30 min exhibited 100, 95, and 85% immobility, respectively, during postexposure observation. Ceriodaphnia dubia and H. azteca exposed to Zn for as short as 30 min exhibited 100 and 30% immobility, respectively, during postexposure observation. Ceriodaphnia dubia exposed to phenol exhibited recovery of mobility after the exposure period. The presence of delayed effects or organism recovery suggests that toxicity tests used to monitor brief exposures should use environmentally relevant exposure durations and postexposure observations.

Effects of Low Oxygen and High Carbon Dioxide Atmospheres on the Chilling Sensitivity of Cucumber Seedlings

Crops with origins in tropics and subtropics undergo physiological injury when subjected to nonfreezing temperatures below 12°C. Application of heat and chemical shocks to tissue prior to chilling induces chilling tolerance. This study was undertaken to investigate the effects of low oxygen and high carbon dioxide atmospheres on subsequent chilling tolerance. Cucumber seedlings (Cucumis sativus L., cv. Poinsett 76) with radicles 8 to 12 mm long were subjected to 0% to 21% oxygen and/or 0% to 20% CO2 atmospheres for 0 to 72 hr at 2.5 or 15°C. After chilling, they were placed at 25°C for three additional days. Radicle growth was used to assess chilling injury. Modification of the individual germination plates was necessary to ensure seedling exposure to the desired atmospheres. Chilling injury was reduced by exposure to oxygen levels below 1% and to carbon dioxide levels above 5%. Effects of brief exposures were small in comparison to prolonged exposures during chilling. Seed to seed variability was high and obscured some results. The effects of the various atmospheres were greater with the less vigorous seedlings.

Study of the Effects of Brief Exposure to an Organophosphorous Insecticide (Methidathion) on Blood Characteristics of Carp (Cyprinus carpio)

1. Carp with the dorsal aorta cannulated have been used to study the effects of a 5 hour exposure to methidathion at concentrations of 2 or 6 mg/litre. Blood samples taken during control, exposed and recovery periods were used to determine plasma acetylcholinesterase (AChE) activity, haematocrit value, mean cell volume, total plasma protein, and filtration time through Nucleopore filters containing pores of 8 microns. 2. A drastic inhibition of AChE activity was observed and this continued during the recovery for at least 5 days. Changes in other blood parameters were less marked and recovered soon after fish were returned to non-polluted water. The increased haematocrit and decrease in filtration time suggests some impairment of gas transfer during exposure but the depletion of AChE activity and associated muscular and neural disturbances are more serious results of pollution with this organophosphate insecticide.

The reinforcing effects of brief exposures to nitrous oxide in healthy volunteers

The reinforcing and subjective effects of brief (about 1.5 min) exposures to nitrous oxide, ranging from inspired concentrations of 20–80% in oxygen, were examined in 11 healthy volunteers. A choice procedure was used in which during each of four sessions, subjects first sampled a given concentration of nitrous oxide and placebo oxygen, and then chose between the two. 20, 40, 60 and 80% nitrous oxide were chosen by five, four, three, and three subjects, respectively—these choice levels did not exceed that of chance. All concentrations had psychoactive effects, and in general, concentration-related subjective effects were found. We conclude that in a medical setting, nitrous oxide inhaled in a manner similar to that when used recreationally in a naturalistic setting, does not function as a reinforcer across a wide range of concentrations, in subjects with a modest lifetime history of psychoactive drug use.

Spatial learning in deer mice: sex differences and the effects of endogenous opioids and 60 Hz magnetic fields.

We examined the effects of brief exposure to weak 60 Hz extremely low frequency (ELF) magnetic fields and opioid systems on spatial behavior and learning in reproductive adult male and female deer mice, Peromyscus maniculatus. Sex differences were evident in spatial performance, with male deer mice displaying significantly better performance than female mice in the Morris water maze, whereby animals had to acquire and retain the location of a submerged hidden platform. Brief (maximum 5 min) exposure to weak (100 microT) 60 Hz magnetic fields during task acquisition significantly improved female performance, eliminating the sex differences in acquisition. The opiate antagonist, naltrexone, also improved female acquisition, though significantly less than the magnetic fields. These facilitatory effects involved alterations of "non-spatial" (task familiarization and reduction of related anxiety/aversive related behaviors) and possibly "spatial" aspects of the task. Enhancement of enkephalin activity with the enkephalinase inhibitor, SCH 34826, significantly reduced task performance by male deer mice. Both naltrexone and the 60 Hz magnetic fields attenuated the enkephalin mediated reductions of spatial performance. These findings indicate that brief exposure to 60 Hz magnetic fields can enhance water maze task acquisition by deer mice and suggest that these facilitatory effects on spatial performance involve alterations in opioid activity.

Sexually dimorphic aspects of spontaneous activity in meadow voles (Microtus pennsylvanicus): Effects of exposure to fox odor.

In this study, a multivariate analysis of the locomotor activity of adult, breeding male and female meadow voles (Microtus pennsylvanicus) was conducted. Overall, male voles made more movements and spent more time in the center of the activity chambers than did female voles. The authors further investigated the effects of brief exposure (3 min) to predator (red fox [Vulpes vulpes]) odor and various control odors (butyric acid, extract of orange) on subsequent activity. Control odors had no effects. Immediately following exposure to the fox odor, male voles exhibited significantly lower levels of activity and decreased center time. No significant changes in any activity variable were observed in the female voles following exposure to fox odor. This study provides evidence for sex differences in both basal activity levels of meadow voles and activity following exposure to a predator odor.