Perseveration of attention to conspecific odors and novel objects in castrated gerbils

Castrated male and female gerbils were tested for odor preference and for attention to conspecific odors and a novel object. Castrated gerbils housed with sham-operates preferred home odors, discriminated between two groups of male gerbils by olfactory cues, and perseverated in attention to odors of male gerbils and to a novel object. Similar perseveration to male conspecific odors was shown in gerbils given injections of L-DOPA (30 mg/kg). Combined treatment (castration and L-DOPA) resulted in additive effects on perseveration. This research challenges two general hypotheses of gonadal hormone function. The first, that changes in odor preference after castration are due to a loss in testicular androgen, is insufficient, because (1) female as well as male gerbils showed similar perseveration to odors, (2) there was a significant correlation between LH and duration of investigation of male conspecific odors, and (3) L-DOPA, the dopamine precurser, also caused perseveration to conspecific odors. The second, that gonadal hormones are responsible for persistence of attention, cannot be broadly generalized, because castration with resultant elevation of LH and regression of ventral glands resulted in perseveration of attention in male and female gerbils.     

Sensitization of sympathetic-adrenal medullary responses to a novel stressor in chronically stressed laboratory rats

Studies from this and other laboratories have demonstrated that sympathetic-adrenal medullary responses are reduced in laboratory rats exposed to chronic intermittent stress. To extend these findings, we have conducted three experiments in which laboratory rats were exposed daily for 26 consecutive days to the same (homotypic) stressor and then challenged with a novel (heterotypic) stressor. Each stress session lasted for 30 minutes and the following homotypic/heterotypic treatments were included: Experiment 1--restraint/footshock; Experiment 2--cold swim/restraint; and Experiment 3--footshock/cold swim. Controls were exposed to the heterotypic stressor only. Plasma levels of norepinephrine (NE) and epinephrine (EPI) were measured in blood samples taken from control and chronically stressed rats to provide an assessment of sympathetic-adrenal medullary activity. In each experiment, chronically stressed rats gained significantly less weight than handled controls. Basal plasma levels of NE and EPI were similar for chronically stressed and control rats. In contrast, plasma catecholamine responses to the heterotypic stressor were significantly greater in stressed rats compared to controls that were stressed for the first time. This pattern of exaggerated responses was especially evident for the cold swim/restraint and footshock/cold swim groups. These findings provide evidence for a sensitization of sympathetic-adrenal medullary responses to a novel stressor in animals previously exposed to chronic intermittent stress.     

Multiple exposures to familiar conspecific withdrawal is a novel robust stress paradigm in ewes

Paradigms used so far to study the effects of social isolation in sheep confound the effects of social isolation with those of other stressors (e.g. new environment) and showed contradictory effects after multiple social isolations. We propose here to characterize and examine the repeatable effects of social isolation induced by the familiar conspecific withdrawal (FCW). This latter test consists of socially isolating the ewe by the removal of group mates from the room test for 3 h. Behavioral and endocrine responses of adult ovariectomized-estradiol implanted ewes were compared 90 min before and 90 min after FCW, which was applied three times every fourteen days. We observed that each FCW induced significant increases in plasma cortisol level, in the number of vocalizations, foot pawing, circling attempts and a significant decrease in time spent lying down. An increase in plasma cortisol levels and decrease in duration of maintenance behaviors were significantly lower after the third FCW than after the first one. These differences could be explained by higher plasma cortisol levels and lower duration of maintenance behaviors before the third FCW than before the first FCW suggesting an anticipation of the social isolation period. These data indicate that social isolation is sufficient to induce distress with stable stressful responses after multiple exposures to familiar conspecific withdrawal.     

Ultrasounds in neonatal rats: Novel,predator and conspecific odor cues

Neonatal rat ultrasound repetition rates were monitored in response to 6 odor cues, including 1 novel, 2 predator, and 3 conspecific olfactory stimuli. Contrary to predictions of previous studies, predator odor did not elicit consistently low call rates. A significant difference was detected between litters tested with the same odor cue for the foreign and predator odor treatments. Odor was the only significant effect to explain differences in neonatal ultrasonic responses to conspecific odor treatments. Call rates recorded for the novel lactating female odor were significantly greater than those for the home bedding and adult male odors. Odors associated with the home cage or with an adult male elicited low call rates.     

Effects of fluprazine hydrochloride on conspecific odor preferences in rats

The effect of Fluprazine Hydrochloride (DU 27716) on preference for conspecific male, estrous female and food odors was examined in male rats utilizing a two-compartment choice apparatus. Treatment with 8.0 mg/kg Fluprazine enhanced the preference of males for male odors but had no effect on preference for either estrous female or food odors. The drug-induced enhancement of male odor preference is consistent with the suggestion that Fluprazine interferes in some way with the processing of olfactory stimuli which normally precede offensive attack. The failure of the drug to alter the preference of males for estrous female odors suggests that the increased sniffing of estrous females noted during social testing may be secondary to other sources of conspecific stimulation or may reflect a highly transitory effect on olfactory processes. These results suggest that the suppressive effects of Fluprazine on intermale aggression and copulation are mediated by somewhat distinct mechanisms.     

Appetitive conditioning in neonatal rats: Conditioned orientation to a novel odor

These experiments document a form of early appetitive learning in rats obtained using classical conditioning procedures. Some of the special determinants of this conditioning are described, as well as ontogenetic changes in the effectiveness of training procedures. Learning was apparent when deprived 3- and 6-day-old rats oriented to and maintained contact with a novel and normally aversive odor after this odor had been paired with oral infusions of milk (Experiment I). The effectiveness of the conditioning procedures depended on the temperature at which pups were trained (Experiment IB). Moreover, the reinforcing properties of milk infusions depended on deprivation (Experiment IC). This conditioned change in responsiveness to odor was specific to the odor that had been paired with milk (Experiment II) and was retained for at least 24 hr (Experiment III).     

The spatial distribution of visual attention in developmental dyslexia

The present study investigated the spatial distribution of visual attention in dyslexic and normally reading children. The performances of the two groups were investigated using two different paradigms. In experiment 1 we analyzed the distribution of processing resources both inside and outside the focus of visual attention by simply recording reaction times to the detection of a white dot target projected at different eccentricities from the fovea. The distribution of attentional resources differed significantly between the two groups of children. The eccentricity of the stimulus was significant only for normally reading children - who showed a normal gradient - as it influenced their detection speed, whereas it had no effect on dyslexic children, who exhibited a diffused distribution of visual processing resources inside the visual field. In experiment 2 we studied the distributed (unfocused) mode of attention in a visual search task by measuring reaction times to a target stimulus inside a large configuration with a variable number of distractors. Results show that as compared to normal children dyslexics are better able to distribute their attentional resources diffusely. Our conclusion is that reading disability may be characterized by a diffused distribution of visual processing resources. These data might be interpreted in the framework of studies on magnocellular deficits in dyslexia, whereby the anomalous distribution of visual attention might explain how transient pathway functioning influences the reading process.     

Persistence of rat parvovirus in athymic rats

Summary Euthymic (SD or outbred rnu/+) and athymic (rnu/rnu) rats were inoculated oronasally or intraperitoneally with the RV-Y strain of rat virus when they were 2 days or 4 weeks old. Clinical signs of infection in athymic infants were similar to those in euthymic infants, but significantly more athymic infants died. Some infants developed anemia and thrombocytopenia. After inoculation of infants, RV-Y was detected in surviving euthymic rats for 7 weeks and in surviving athymic rats for at least 10 weeks. After oronasal inoculation of 4 week-old rats no clinical illness was observed. RV-Y persisted less than 6 weeks in juvenile euthymic rats but at least 12 weeks in athymic juvenile rats. Intraperitoneal inoculation of juveniles resulted in infection for at least 6 weeks. The antibody response of athymic rats to RV-Y was significantly reduced compared to that of euthymic rats. These studies indicate that T cell deficiency increases the severity and duration of RV infection and imply that T cells are required for the full expression of resistance to RV infection. They also suggest that RV-Y induced anemia could serve as a model for human parvovirus-induced anemia.     

Haemophilus infection in a colony of laboratory rats

During routine quality control of laboratory rodents, short gram-negative rods with satellite growth adjacent to a Staphylococcus strain were isolated from rats. They proved to be members of the family Pasteurellaceae. On the basis of their dependence on V factor they were classified as Haemophilus sp. Systematic investigations in our laboratory rat colony revealed a high prevalence of these bacteria. They were isolated from 75 of 446 rats (16.8%) which were monitored by culture during a 2-year investigation. Most strains were isolated from the lungs and the trachea; some were cultured from the nasal cavity and the female genital tract. Antibodies to these bacteria were detected in sera from 385 of 829 rats (46.5%) by using an indirect immunofluorescence test. The majority of culturally and serologically positive animals came from three separate holding areas; they all came from the same breeder. Investigation of rats immediately on receipt from the breeder showed that they were culturally and serologically positive for Haemophilus sp. Histological examination of rats which were monoinfected with Haemophilus sp. showed a mild inflammatory cell infiltration in the lungs and a light diffuse hyperemia. In the physiological and biochemical investigations of 53 isolates, all strains had an identical biochemical profile. On the basis of the 35 criteria examined, a definite classification is not possible. These Haemophilus bacteria are probably members of a hitherto unknown species.     

Response to novelty of various types in laboratory rats

One purpose of the two studies reported here was to examine the reactions of rats to changes in the spatial arrangement of a familiarized environment under low stress conditions. The second purpose was to test the role of rats' experience with novelty. In Experiment I the novelty was manipulated by introducing new tunnels into one zone of the experimental chamber. The introduction of novelty took place after 11 habituation sessions. In Experiment II in the course of habituation sessions the experimental group of rats was subjected to a persistent change of tunnel arrangement in the experimental zone, whereas for the control group nothing changed. All animals reacted to the novelty with increased time spent in the experimental zone and decreased time spent in other zones. Both experiments show that under low stress conditions rats demonstrate a positive response toward novelty and that their previous experience with novelty does not affect that reaction.     

Screening of toxic-haemolytic anaemia in laboratory rats: a model of phenylhydrazine-induced haemolysis

An increase of the plasma haemoglobin level was found to be a reliable characteristic of toxic-haemolytic anaemia induced by a single dose of phenylhydrazine in laboratory rats. Very high doses of the substance increased the changes in many other characteristics to an extent that was up to now observed only for haemolytic events.     

Fetuin-A levels in obesity: differences in relation to metabolic syndrome and correlation with clinical and laboratory variables

Introduction

Fetuin-A is an important player in the enhancement of insulin resistance. There are very limited data available concerning the relationships between fetuin-A, weight status and features of the metabolic syndrome (Met S) in obese Egyptian subjects, and especially in children. The aim of the study was to evaluate fetuin-A serum level in subjects with obesity and its possible association with other laboratory and clinical variables.

Material and methods

A total of 140 obese subjects and 50 controls aged 10-40 years were recruited. Demographic, anthropometric and biochemical features were collected according to a standard protocol. Serum fetuin-A levels were measured using ELISA and the modified Third Report of the National Cholesterol Education Program (NCEP-ATP III) criteria were adopted to diagnose Met S.

Results

A higher level of serum fetuin-A was detected in obese subjects. Met S cases were also significantly associated with higher serum fetuin-A. Fetuin-A correlated significantly with BMI (r = 0.437), systolic (r = 0.228) and diastolic blood pressure (r = 0.295), waist circumference (r = 0.332), insulin resistance calculated by the homeostasis model (HOMA-IR) (r = 0.295) and high-density lipoprotein (HDL) (r = 0.362).

Conclusions

Fetuin-A levels were higher in adults and children with obesity and Met S. They were related to insulin resistance and to features of the Met S in cross-sectional analyses. Our study demonstrates a novel association between human fetuin-A and the Met S among obese subject. Therefore, fetuin-A might be a new promising link between obesity and its comorbidities.     

Selective attention to pain: a psychophysical investigation

Laboratory research suggests that the processing of painful stimuli can be modulated by selective attention to a particular sensory modality. However, alternative accounts for previous findings remain possible in terms of task-switching and spatial attention effects. In the present study, we examined whether attention can be selectively directed to the pain modality in order to facilitate the processing of the sensory-discriminative aspects of painful laser heat stimuli when these alternatives were ruled out. Participants made speeded spatial discrimination responses to an unpredictable sequence of painful laser heat and visual stimuli presented on the left forearm. On each trial, a symbolic cue predicted the likely modality for the upcoming target on the majority of trials. Participants responded more rapidly when the target was presented in the expected as opposed to the unexpected modality, demonstrating that selective attention can modulate the processing of painful stimuli. These findings are discussed in relation to contemporary theories of crossmodal attention and multisensory information-processing.