DNA excision repair as a component of adaptation to low doses of ionizing radiation in Escherichia coli

The effects of chronic lithium chloride infusions on consumption of, and subsequent preferences for, a novel diet were examined in rats with ablations of the area postrema (AP) and sham-lesioned control rats. Osmotic minipumps (Alza), filled with a saturated aqueous solution of LiCl (63 g/100 ml), were implanted in the peritoneal cavity of half of the lesioned rats (n = 9) and half of the control rats (n = 8). The remaining rats received empty pumps (n = 9 and n = 7 for lesioned and controls, respectively). The LiCl or sham drug phase was paired with free access to a highly palatable novel diet (AIN diet) during a 7-day conditioning period. Subsequent preferences for the novel diet relative to a familiar diet (ground Purina lab pellets) were determined using a two-food choice procedure. The only group to show a persistent and significant reduction in novel food consumption during the conditioning phase was the sham-lesioned group infused with LiCl (p < 0.01). This group also exhibited a marked aversion for the novel diet, indicative of a conditioned food aversion (CFA), during the preference tests. No significant differences in novel diet consumption or in novel diet preference were found between the two AP-lesioned groups. This study provides evidence that anorexia and CFAs to a novel diet, induced with chronic infusions of lithium, are abolished by destruction of the chemosensitive area postrema.     

Effects of hypothermia on the acquisition of conditioned taste aversion in rats.

Analyzed the mechanism of conditioned taste aversion (CTA) by subjecting 131 male and hooded rats in 5 experiments to reduced body temperature during various phases of CTA acquisition. A 15-min access to .1% saccharin served as the CS, and an ip injection of LiCl (.15 M, 4% of body weight) given 30 min later served as the UCS. Hypothermia (cooling to 20-22°C colonic temperature) alone or combined with anesthesia (Nembutal 20 or 40 mg/kg) did not prevent CTA acquisition when applied during the CS-UCS interval. Hypothermia induced immediately after LiCl administration to anesthetized or unanesthetized Ss failed to disrupt CTA or to increase neophobic rejection of saccharin. On the other hand, hypothermic Ss were not able to form the short-term gustatory trace when the CS (2% saccharin, 1% of body weight) was injected ip, although this procedure yielded significant CTA in euthermic Ss. It is concluded that the most vulnerable link of CTA acquisition is the formation of the short-term gustatory trace. Persistence of the short-term trace, its association with poisoning, and consolidation of the permanent CTA engram are accomplished by mechanisms that are resistant to hypothermia and/or anesthesia. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory cues mediate food selection by young chicks

An illness-induced aversion paradigm was used to assess the possible influence of olfactory cues on food selection by young chicks. At 2-3 days posthatching, chicks were exposed briefly to food scented with a novel odor (orange) followed by an injection of LiCl or saline. LiCl-injected chicks subsequently displayed stronger avoidance of orange-scented food than did the controls. Chicks in a second experiment were preexposed to novel-scented food, then either injected with LiCl or not injected. The LiCl chicks, but not the controls, later avoided food associated with the preexposure odor (relative to food treated with an unfamiliar odorant). Two- to three-day-old chicks are capable of associating specific food odors with negative consequences and modify their feeding behavior as a function of such experience.     

Comparison of nutritive and nonnutritive stimuli in intestinal and oral conditioned taste aversion paradigms.

The intestinal taste aversion paradigm has previously demonstrated that animals could orally discriminate between carbohydrate and fat subsequent to pairing a gastrointestinal (GI) infusion of 1 nutrient with lithium chloride (LiCl), whereas they could not discriminate between 2 nonnutritive flavors (A. L. Tracy, R. J. Phillips, M. M. Chi, T. L. Powley, & T. L. Davidson, 2004). The present experiments assessed the relative salience of nutritive and nonnutritive stimuli when presented either intestinally or orally. Two compound stimuli, each comprising 1 nutrient and 1 nonnutritive flavor, were presented in training and were paired with LiCl or saline. Subsequent oral intake of the nutrients alone, the flavors alone, or the compounds was measured. Results showed that rats discriminated both nutrients and flavors independently after GI or oral training, whereas the compounds were discriminated only after oral training, indicating substantive differences in the processing of these stimuli. This suggests that nutrient activation of the GI tract may potentiate learning about nonnutritive flavors analogously to taste-potentiated odor conditioning. The ability to learn about the oral properties of stimuli in the GI tract suggests a new account of delayed taste aversion learning as well as learning about the positive nutritive consequences of food consumption. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned social aversion in the male Mongolian gerbil (Meriones unguiculatus).

Adult male Mongolian gerbils formed conditioned social aversions to young male conspecifics. The basic paradigm consisted of pairing an S with a young animal (test stimulus) for 5 min and then injecting the S with LiCl to produce gastrointestinal distress. When retested 48 hrs later, the S avoided the test stimulus, as indicated by significantly decreased investigation time and approach frequency. Through a series of 5 experiments with 290 Ss on dose level, delay of toxin injection, and stimulus generalization, it was demonstrated that a dose of .03 ml/g of .15 M LiCl was effective, the toxin should be given within 15 min of the preliminary social pairing, the social aversion was specific to the particular first paired stimulus animal, and isolation between test sessions was necessary for an aversion to develop. This paradigm extends knowledge of the learned aversion process and demonstrates that this type of learning can be generalized to a social situation by gerbils. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A failure to find socially mediated taste aversion learning in Norway rats (R. norvegicus).

Three studies with 240 Long-Evans rats investigated whether rats would avoid ingesting a diet as the result of interacting with an ill conspecific that had ingested that diet. Observer rats interacted with conspecific demonstrators immediately after demonstrators ate a novel diet and were made ill by LiCl injection. Following their interaction with demonstrators, observers were tested for aversion to their ill demonstrator's diet. Previous research has shown that (a) an observer can extract information from a demonstrator sufficient to permit identification of the demonstrator's diet and (b) a rat ill from LiCl toxicosis is an adequate UCS in a taste aversion learning paradigm. Two of the present experiments demonstrated that cues emitted by an S, reflecting the particular diet it has eaten, were an adequate CS in a toxicosis-induced aversion learning situation. Observer avoidance of a diet previously ingested by an ill demonstrator was, however, not demonstrated. Implications of the failure to find socially mediated aversion learning are discussed. (10 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Forebrain structures specifically activated by conditioned taste aversion.

This study investigates which forebrain structures show Fos protein expression during conditioned taste aversion (CTA) acquisition and whether Fos expression depends on the aversion strength. A novel taste paired with an intraperitoneal injection of a low dose of the malaise-inducing agent lithium chloride (LiCl) induced a weak CTA, whereas associating this novel taste with a high dose of LiCl induced a strong CTA. Increasing the strength of the gastric malaise alone enhanced Fos expression in central, basal, and lateral amygdala nuclei and decreased Fos expression in the nucleus accumbens core. Taste-malaise association induced specific Fos activation in the insular cortex (with both the low and the high doses of LiCl) and the nucleus accumbens shell (with the high LiCl dose only). No significant variation of Fos expression was measured in the perirhinal cortex. Several forebrain areas may be sites of taste-malaise convergence during CTA acquisition depending on the strength of the aversion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disruption of saccharin-aversion learning in rats by cortical spreading depression in the CS-US interval.

Taught 80 rats to associate the flavor of saccharin (.1%) with the sickness produced by ip injection of 100 mg/kg of lithium chloride (LiCl) 5 hr. after drinking. A choice test on the next day revealed 90% saccharin preference in naive Ss and 80% water preference in the training group. Bilateral cortical spreading depression (CSD) interfered with the aversion most clearly when applied 3 hr. after saccharin ingestion. Less complete aversion was induced when CSD was elicited 5 min. after saccharin administration or 15 min. before LiCl injection. The CSD evoked 5 min. after LiCl injection was without any amnesic effect. It is suggested that the cortical gustatory trace prolongs the temporal storage of taste cues at the bulbar level and helps to bridge the long CS-UCS delays typical for gustatory-visceral learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chronic lithium chloride infusions: Conditioned suppression of food intake and preference.

Developed a modified learned food aversion paradigm that simulated the prolonged food and illness exposure likely to characterize nutrient deficiencies or tumor growth. In this paradigm, a continuously available food was associated with a slow, continuous infusion of LiCl provided by an osmotic minipump. In Exps I and II, 68 rats were implanted with minipumps with LiCl or with empty pumps and exposed to novel or familiar diets. In Exp III, conducted with 40 Ss, the variable was prior exposure to the same diet. Significant aversions were acquired when the available diet was novel but not when it was familiar. Effects of drug infusions on daily food intake paralleled those on aversion formation. Marked, persistent suppression of food intake was seen in drug-treated Ss consuming a novel diet, but only transient declines were seen in those with a familiar diet. By separating the direct from the conditioned effects on food intake of chronic drug infusions, these studies provided strong evidence that learned food aversions can lead to anorexia. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of UVB on the synthesis of complement proteins by keratinocytes

Conditioned taste aversion is a common classic conditioning procedure used to identify noxious stimuli. When a rat is given a taste solution, the conditioned stimulus (CS), followed by an unpleasant experience, the unconditioned stimulus (US), the rat will avoid consumption of the CS in future presentations. These experiments use the taste aversion procedure to examine the effect of exposure to a high magnetic field. A solution consisting of 3.0 g glucose and 1.25 g saccharin per 1 L of solution (G+S) was used as the CS and a 9.4-T magnet served as the US. In Experiment 1, all rats received a 10 min presentation of the G+S solution followed by either a 30 min exposure to the magnetic field (Magnet, n = 8), a 30-min exposure in a container with similar conditions but lacking the magnetic field (Sham, n = 8), or no exposure (Control, n = 8). The Magnet Group showed a taste aversion on the first day of preference testing (p < 0.05). Experiment 2 employed the same US-CS protocol for 3 consecutive days of conditioning. The Magnet Group demonstrated a taste aversion for the postexposure Days 1-8 (p < 0.01). There was no difference between the Sham and Control Groups in either experiment. The results of this study clearly demonstrate that the rats associated the G+S solution with the experience of being exposed to the high magnetic field and avoided the solution in subsequent presentations.     

Attenuation of ethanol-induced conditioned taste aversion in mice sensitized to the locomotor stimulant effects of ethanol.

This study examined the effect of repeated ethanol (EtOH) injections that induced behavioral sensitization on subsequent acquisition of EtOH- and lithium chloride (LiCl)-induced conditioned taste aversion (CTA). CTA acquisition was assessed in independent groups of EtOH-sensitized and nonsensitized genetically heterogeneous female mice after injections of saline; 1, 2, or 4 g/kg EtOH; or 2 or 4 mEq/kg LiCl. Saline and 1 g/kg EtOH did not induce CTA. Four g/kg EtOH and 4 mEq/kg LiCl induced similar levels of CTA in EtOH-sensitized and nonsensitized groups. CTA induced by 2 g/kg EtOH and 2 mEq/kg LiCl was attenuated in EtOH-sensitized mice compared with nonsensitized counterparts. Thus, a sensitizing regimen of EtOH preexposure resulted in both a decrease in EtOH and LiCl aversion and an increase in EtOH locomotor sensitivity; such changes could ultimately contribute to enhanced EtOH intake and potentially to EtOH abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The US-Preexposure Effect in Lithium-Induced Flavor-Aversion Conditioning Is a Consequence of Blocking by Injection Cues.

In 2 experiments, rats received flavor-aversion conditioning in which the unconditioned stimulus (US) was an orally consumed solution of lithium chloride (LiCl). The resulting aversion was not attenuated by giving preexposure to injections of LiCl, although such preexposure did attenuate aversions established using injected LiCl as the US (Experiment 1). This outcome suggests that blocking by injection-related cues is responsible for the US-preexposure effect observed in this situation. Experiment 2 confirmed this interpretation by showing that presenting such cues (by giving an injection of saline) at the time that the LiCl was drunk resulted in an attenuation of conditioning in animals preexposed to injections of LiCl. The US-preexposure effect obtained in these experiments can be explained solely in terms of blocking by injection cues, although other mechanisms may contribute to the effect seen in other flavor-aversion paradigms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learned aversions to copulatory behaviors in male rats.

Used LiCl for an aversive effect on copulatory behavior in adult experienced and inexperienced male hooded rats (Exp I) and in inexperienced adult male Holtzman rats (Exp II). When males received an injection of LiCl immediately after an encounter with an estrous female, the vigor of subsequent copulatory responding was initially unaffected. After 5–20 such pairings, however, males displayed an aversion to copulatory behaviors; they ceased to copulate entirely. These aversions persisted when Ss were tested in a novel environment and extinguished after 4 nonreinforced trials. This multiple-trial adaptation of the conditioned taste aversion paradigm provides a new approach to the aversive control of sexual behavior. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Within-compound learning with US presentation in taste aversion.

Determined whether the presentation of a LiCl unconditioned stimulus/stimuli (UCS) disrupts within-compound learning in a taste aversion preparation, using 30 male and 32 female rats in 3 experiments. In Exp I, Ss showed stronger associations between 2 solutions presented in a compound when the compound was followed by LiCl. Exp II showed that an immediate LiCl injection produced stronger flavor–flavor association than a delayed injection. Exp III provided a comparison with Ss that did not receive the treatment to enhance consumption of salty solutions. Results indicate that the effects of Exp II depended on the treatment that altered consumption of 1 component. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of the interoceptive sensory consequences of CCK, LiCl, and satiety in rats.

In three experiments we assessed the degree to which ad lib feeding, injection of cholecystokinin (CCK), and injection of lithium chloride (LiCl) produce states with similar sensory consequences. In each experiment, two groups of rats were trained to use cues arising from food deprivation and satiation of discriminative signals for shock. One group was shocked when deprived but not when nondeprived. The other group received the reversed discrimination. Testing began when incidence of freezing was greater under the shocked deprivation than under the nonshocked deprivation condition. In Experiment 1, the rats were tested under 24-hr food deprivation after injections of CCK, LiCl, and saline (in counterbalanced order). The effects of CCK on freezing did not differ from those of saline, whereas both CCK and LiCl had effects that were different from ad lib feeding. This pattern of results was also obtained when deprivation level during training and testing was reduced to 8 hr (Experiment 1A) and also when rats received small amounts of food in conjunction with CCK (Experiment 2). The intubation of a high-calorie stomach load (Experiment 1A) produced a response profile like that observed after free feeding. Freezing after LiCl treatment differed from that observed after free feeding and from that found after injection of CCK. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increased immune activation precedes the inflection point of CD4 T cells and the increased serum virus load in human immunodeficiency virus infection

In sickness-conditioned learning, animals become ill after sampling a new substance and develop an aversion that is expressed as avoidance of that substance in subsequent presentations. We examined the parameters of a one-trial, nongustatory, sickness-conditioned learning task in day-old chicks. Chicks pecked a bead and were made ill by i.p. injection of lithium chloride (LiCl). Both 0.5 and 1.0 M LiCl (0.1 ml) produced reliable avoidance at test. Chicks injected with LiCl between 15 and 45 min after training avoided the bead at test, whereas those injected within 5 or 10 min or more than 45 min after training did not. Avoidance was present until 24 h posttraining and absent after 48 h. Therefore, robust learning of the sickness-conditioned learning task occurs in one trial without the need for gustatory cues, and memory for the task lasts at least 24 h. Uses of this task to study memory formation in the day-old chick are discussed.     

Toxocara canis infection in the paratenic host: a study on the chemosusceptibility of the somatic larvae in mice

A research on formulation and dosage strategies of anthelmintics have been conducted in mice experimentally infected with eggs of Toxocara canis. Multidose treatments commenced at days 2, 14, 81, 87 and 123 postinfection. Results indicated no detectable difference in the chemosusceptibility of the migrating early infection larvae and the resting hypobiotic chronic infection larvae. Application of medicated dry food (pellets) may be a simple way of improving efficacy of treatment compared to oral drenching. The larvicidal potential of fenbendazole (FBZ), albendazole (ABZ), flubendazole (FUBZ), oxibendazole (OBZ) and ivermectin was assessed. Reductions of 84.2 to 99.7 or 88.8 to 100% of group mean larval counts were recorded after 20-30-day courses of feeding pellets containing FBZ at 6 g kg-1 or ABZ at 1.6 g kg-1 food, respectively. Efficacies of 57.8 to 88.2 or 81.1 to 32.0% were achieved by 20-day courses of feeding pellets medicated with FUBZ and OBZ at 1.6 g kg-1 or 6.0 g kg-1 food, respectively. Ivermectin at various dosing regimens showed only moderate larvicidal potential. Efficacy rates were not closely correlated with the amount of drug taken by the animals. The blood-brain barrier is permeable for the anthelmintics tested, and the brain of mice does not provide a site promoting survival of larvae.     

Rationale for en bloc vein resection in the treatment of pancreatic adenocarcinoma adherent to the superior mesenteric-portal vein confluence. Pancreatic Tumor Study Group

The enzymatic activity of protein kinase C (PKC) was measured in the cytosol and particulate fraction of parabrachial nucleus, the presumed site of conditioned taste aversion (CTA) engrams. At various time intervals after acquisition of the task (pairing saccharin consumption with subsequent LiCl poisoning) the nucleus was dissected from the frozen coronal sections. An increase (+40%) in the cytosol PKC activity was found 48 h after that pairing in comparison with controls (saline injection instead of LiCl). Particulate enzyme activity virtual did not change (-5%). Thus the total PKC activity increased significantly (21%). Qualitatively similar but less markedly expressed PKC shifts (+18% in cytosol) ere found 24 h following CTA. Twelve hours and 5 days after CTA acquisition the activity and distribution of PKC was similar to that seen in normal rats. The control experiments revealed that 6 h after LiCl injection alone (without previous saccharin consumption) translocation of PKC from the cytosol to the membrane fraction (found previously 1 h after LiCl injection alone) still persisted but did not differ from that found 6 h after its pairing with saccharin drinking (CTA). It is concluded that acquisition of conditioned taste aversion may be followed by synthesis of PKC rather than by its translocation or downregulation.     

Effect of intracranial electrical stimulation on the primary learned aversion to LiCl and the generalized aversion to NaCl.

Notes that following LiCl intoxication rats develop an aversion to the substance and will, by generalization, refuse to ingest similarly tasting equimolar solutions of NaCl. Prolonged electrical stimulation of the brain during the period immediately following ingestion of LiCl has previously been found to disrupt the generalized NaCl aversion. Results of the present 3 experiments with a total of 47 male Holtzman albino rats establish that such continuous long-term stimulation of diencephalic and telencephalic loci effectively eliminates the generalized NaCl aversion but leaves the primary learned aversion to LiCl intact. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of transforming growth factor beta one (TGF-beta 1) on wound healing, with or without barrier membranes, in a Class II furcation defect in sheep

The purpose of this study was to analyse the effect of TFG-beta 1 on wound healing in standardized Class II furcation defects of 48 mandibular second premolar teeth in 24 sheep. The experimental design included a control group (carrier only, 25% pluronic F-127), and 2 experimental groups: group A (80 micrograms/ml TGF-beta 1 + carrier) and group B (80 micrograms/ml TGF-beta 1 + carrier covered with a barrier membrane). Sheep were killed either 2 wk or 6 wk after surgery. Mesiodistal sections of the decalcified specimens were quantified histologically using stereology. Percentage volumes of regenerated bone, fibrous connective tissue and cementum were calculated for each furcation defect. Mean values were analysed using multiple ANOVA; p values were calculated using paired and unpaired Student's t-tests. After 2 wk there was more bone in group B than either of the other 2 groups, but this was not statistically significant. By 6 wk more bone was present in group A than in the control group (p < 0.02) and also in group B when compared with both group A and the control group (p < 0.02 and p < 0.44), respectively. In the 4 wk between sampling significantly more bone had formed (group A < 0.05 and group B p < 0.003, respectively). A negative correlation existed between volumes of bone and fibrous connective tissue and no significant differences between the volumes of cementum were evident between any of the groups. This study demonstrated that TGF-beta 1 encouraged bone regeneration in Class II furcation defects in sheep, an effect enhanced by the presence of a barrier membrane. This is the first report on the use of TGF-beta 1 in conjunction with GTR in periodontal defects.