The structure and switchable dielectric properties of a dabco complex with chromium chloride.

We report a metal-organic material of the following formula [DabcoH22+]·CrCl3(H2O)3·2(Cl-) (DabcoH22+ = C6H14N22+, diprotonated 1,4-diazabicyclo[2.2.2]octanium). This compound exhibits a dielectric anomaly, which is attributed to the rotatory fluctuation of the Dabco molecule. The complementary results of single-crystal X-ray diffraction, DSC, dielectric, NMR and Raman spectroscopy provide information about the general mechanisms of the phase transition, which results from the ordering of the DabcoH22+ molecules. The reversibility of dielectric switching with no observable attenuation of the dielectric signal during multiple cycling is observed. The dielectric switching characteristic of the crystal makes it an interesting material for potential application in smart devices.

Remote activation and detection of up-converted luminescence via surface plasmon polaritons propagating in a silver nanowire.

In this paper, we demonstrate remote activation and detection of the 2-photon up-conversion luminescence via surface plasmon polaritons propagating in a long silver nanowire. The hybrid nanostructure was assembled by locally depositing a submicron droplet of nanocrystal-containing colloidal solution on one of the ends of the metallic nanowire. When - using a classic confocal microscope - the second end of the nanowire, without the nanocrystals, is illuminated with infrared laser light, we observe strong emission from the same end. Therefore, it indicates that surface plasmon polaritons activated with infrared light at the second end of the nanowire propagate along it and can excite nanocrystals in the droplet at the opposite end. Subsequently, the excited nanocrystals up-convert the energy and by launching surface plasmon polaritons can guide the up-converted luminescence back to the starting point. The emergence of this effect is much more pronounced for a laser polarized along the nanowire. The spectral and temporal character of this emission reveals strong interactions between surface plasmon polaritons and electronic states of the nanocrystals. The details of local and non-local aspects of the effects of remote excitation and guiding of energy in a silver nanowire are elucidated using a unique experimental setup, based on two microscope objectives for spatial separation and control of both excitation and emission beams.

Nutrient digestibility in Arctic fox (Vulpes lagopus) fed diets containing animal meals / Digestibilidade dos nutrientes em raposa polar (Vulpes lagopus) alimentada com dietas que continham farinhas de origem animal

Three digestibility experiments on Arctic foxes were carried out. Control groups were fed standard diets (C1 and C2) composed of fresh or frozen animal by-products and steamed ground grain. Dry experimental diets (E1 and E2) contained animal meals, extracted meals and fat, were mixed with water prior to administration. In a preliminary experiment, the digestibility of dry diet E1 moistened with water for 15min and 24h was compared to determine the optimum moistening time during the experimental period proper. The preliminary experiment showed that moistening time had no significant effect on digestibility. In the main experiment, two independent digestibility trials were performed to compare the digestibility of diets fed to foxes during growth (C1 vs. E1) and fur development (C2 vs. E2). Better nutrient digestibility was noted for control diets, compared to experimental. The greatest differences were reported for total protein digestibility. Protein contained in meals undergoes denaturation during heat treatment, which reduces digestibility. It was found that the retention of nitrogen in relation to nitrogen digestion was higher in foxes fed experimental diets (E1 and E2).

Realizaram-se três ensaios de digestibilidade em raposas polares. Os grupos controles receberam dietas-padrão (C1 e C2) compostas por subprodutos de origem animal frescos ou congelados e sementes de cereais em grão. As dietas secas (E1, E2) usadas nos ensaios que continham farinha de origem animal e sementes em grãos extrudadas eram hidratadas antes de administradas. Em ensaio preliminar, avaliou-se a digestibilidade da dieta seca E1, submetida a 15 minutos e a 24 horas de hidratação. Verificou-se que o tempo de hidratação não influenciou a digestão. No experimento principal, foram realizados dois ensaios para comparar a digestibilidade das dietas fornecidas às raposas no período de crescimento (C1 vs E1) e no desenvolvimento de pelo (C2 vs E2). Melhor digestibilidade dos nutrientes foi observada para as dietas controle. As maiores diferenças foram relatadas para a proteína total. A desnaturação das proteínas, durante o tratamento térmico, reduz o índice de digestibilidade das dietas. Observou-se alto teor de retenção de hidrogênio em relação ao hidrogênio digerido nas raposas alimentadas com as dietas E1 e E2.

Fos imaging reveals differential neuronal activation of areas of rat temporal cortex by novel and familiar sounds.

To provide information about the possible regions involved in auditory recognition memory, this study employed an imaging technique that has proved valuable in the study of visual recognition memory. The technique was used to image populations of neurons that are differentially activated by novel and familiar auditory stimuli, thereby paralleling previous studies of visual familiarity discrimination. Differences evoked by novel and familiar sounds in the activation of neurons were measured in different parts of the rat auditory pathway by immunohistochemistry for the protein product (Fos) of the immediate early gene c-fos. Significantly higher counts of stained neuronal nuclei (266 +/- 21/mm2) were evoked by novel than by familiar sounds (192 +/- 17/mm2) in the auditory association cortex (area Te3; AudA). No such significant differences were found for the inferior colliculus, primary auditory cortex, postrhinal cortex, perirhinal cortex (PRH), entorhinal cortex, amygdala or hippocampus. These findings are discussed in relation to the results of lesion studies and what is known of areas involved in familiarity discrimination for visual stimuli. Differential activation is produced by novel and familiar individual stimuli in sensory association cortex for both auditory and visual stimuli, whereas the PRH is differentially activated by visual but not auditory stimuli. It is suggested that this latter difference is related to the nature of the particular auditory and visual stimuli used.

Neither perirhinal/entorhinal nor hippocampal lesions impair short-term auditory recognition memory in dogs.

Visual, tactile, and olfactory recognition memory in animals is mediated in part by the perirhinal/entorhinal (or rhinal) cortices and, possibly, the hippocampus. To examine the role of these structures in auditory memory, we performed rhinal, hippocampal, and combined lesions in groups of dogs trained in auditory delayed matching-to-sample with trial-unique sounds. The sample sound was presented through a central speaker and, after a delay, the sample sound and a different sound were played alternately through speakers placed on either side of the animal; the animal was rewarded for responding to the side emitting the sample sound. None of the lesion groups showed significant impairment in comparison either to their own preoperative performance or to the performance of intact control dogs. This was the case both for relearning the delayed matching rule at a delay of 1.5 s and for task performance at variable delays ranging from 10 to 90 s. From these findings we suggest that the tissue critical for auditory recognition memory is located outside both the perirhinal/entorhinal cortices and the hippocampus.

Cognitive functions of the temporal lobe in the dog: a review.

1 The current paper reviews the role of temporal lobe structures in learning and different kinds of memory, with an emphasis on behavioral tasks that re auditory stimuli. 2 The effects of lesions to structures in the temporal lobe were examined in separate groups of dogs, which were trained on an auditory spatial delayed response, or in a trial-unique auditory delayed match to sample recognition task. 3 Spatial memory was impaired after bilateral hippocampal lesions. On the other hand, neither an anterior temporal lesion or rhinal cortical injury nor combined lesion to the hippocampus and the anterior temporal lobe, affected postoperative retraining and performance of the spatial task. 4 Auditory recognition memory task was not impaired after a hippocampal and/or rhinal cortex lesion. However, postoperative retraining of the task was impaired after a lesion to auditory association areas. 5 These results confirm the role of the hippocampus in spatial memory in the dog. On the other hand, the organization of auditory recognition functions within the temporal lobe appears to be different from those described for visual recognition functions.

Effects of the anterior temporal lobe lesions, separate or combined with hippocampal damage, on spatial delayed responses guided by auditory stimulus.

Seventeen dogs were trained in a three-choice auditory spatial delayed response task, guided by auditory stimulus, at a 10 s delay to a criterion of 90% correct responses in 90 consecutive trials. Four dogs then received bilateral anterior temporal lobe lesions (AT), 6 dogs received hippocampal lesions (H), and 7 dogs served as controls (C). Group C reached postoperative criterion immediately while groups AT and H needed additional training. When subsequently tested at longer delays and with distractions, the group H animals performed more poorly than either the AT or C animals. Further, the group H dogs were again impaired when they retrained at a 10 s delay. In the second phase, the group H and AT animals received a second lesion forming a group (HAT) with bilateral lesions to both the hippocampus and the anterior temporal lobe. Unexpectedly, dogs from group HAT were unimpaired in either postoperative retraining or during performance task and distractions. The results emphasize the importance of the hippocampus in spatial delayed response with an acoustic cue. Effect of combined lesions after extensive training is discussed. Data might support the view, that the hippocampus plays time limited role in memory storage.

Effect of experimental setting on learning and performance of Auditory Delayed Matching-to-Sample task in dogs.

Twelve dogs were trained in a new task for auditory recognition memory: auditory Delayed Matching-to-Sample (DMS). The animals were tested in two experimental settings using approach (Setting 1) or bar-press (Setting 2) responses. At the early stages of training, the learning took more trials in Setting 2, which was caused by different instrumental response and/or different relationship among manipulanda, stimuli, and reward in these two settings. The performance of the final task did not differ between settings and showed a gradual decline with extended delays. No differences were found in responding patterns or in dynamics of learning. Therefore, we conclude that the auditory DMS, trained in either setting, offers a valuable and reliable tool for studies of neural substrate of auditory recognition memory. The detailed analyses of the dogs' behaviour will allow to evaluate the subtle effects of experimental manipulations in future experiments, and for many reasons the data obtained from these two settings may be combined in further analyses.

Thalamic and amygdaloid connections of the auditory association cortex of the superior temporal gyrus in rhesus monkey (Macaca mulatta).

Thalamic and amygdaloid connections of three association auditory areas (AA1, AA2, AA3) of the superior temporal gyrus (STG) were investigated. In order to define the projections of the particular areas, injections of fluorescent tracers were made in three monkeys. Distribution of labeling indicates that area AA1 differs from areas AA2 and AA3 in patterns of both thalamo-cortical and amygdalo-cortical connections. Area AA1 receives its predominant inputs from the ventral and dorsal nuclei of the medical geniculate body (MGB). The amygdaloid projection to the area AA1 originates from the basal nuclei, whereas input from the lateral nucleus was not found. The characteristic thalamic projections to areas AA2 and AA3 originate from the dorsal MGB nucleus and the polymodal nuclei of the posterior thalamus. The density of projections from the dorsal nucleus gradually decreases from area AA1 to area AA3 while projections from the Plm, Sg and Lim nuclei increase in the same direction. Areas AA2 and AA3 are the source of strong connections with the lateral nucleus of amygdala, which density increases progressively when injections shift from area AA2 to AA3. The basal and accessory basal nuclei are the source of a less significant amygdalofugal projections to both cortical areas. Thus, our experimental data indicate that influence of the polymodal thalamic nuclei increases substantially in the direction of the higher order association areas. The strong relation of the same cortical areas with the lateral amygdaloid nucleus might suggest that areas AA2 and AA3, in addition to auditory input are the site of transfer of complex sensory information to the amygdala.

The method of training dogs in auditory recognition memory tasks with trial-unique stimuli.

Three adults dogs were trained in a auditory recognition delayed-matching-to-sample (DMS) task. The experimental setting consisted of one central speaker located in front of the dogs head, two side speakers with nearby response pedals and one rotary food delivery system. Three hundred twenty natural sounds were used as trial-unique stimuli. Sample stimuli were always given through the central speaker. After the delay of 1.5 s, both sample and testing stimuli were activated alternately through the two side speakers. Bar-press response toward the sample stimulus was rewarded by food. The DMS training was continued until attaining a criterion 90% correct responses in 90 consecutive trials. After a control pause, the dogs were retrained to the criterion, and then they were given performance tasks with delays extended to 10-, 30-, 60- and finally to 90-s, in blocks of 90 trials. Dogs required about 1,000 trials of auditory recognition memory training in order to reach the criterion. Their behavior was also stable after the control pause. The dogs performance declined gradually with extended delays reaching an average of 63.4% for the delay of 90 s. Results indicate that the DMS task with auditory stimuli alternating during the testing stage of trial, is a promising method for testing auditory recognition memory.

Investigation of the effect of Angelica sinensis root extract on the proliferation of melanocytes in culture.

Aqueous extracts of Angelica sinensis root, a herb commonly used in the treatment of vitiligo in Traditional Chinese Medicine, were tested for their activity on mouse melanocyte proliferation in culture. At concentrations of 0.5-2500 micrograms/ml, these extracts were not able to stimulate melanocyte cell division. On the contrary, they exerted a general cytotoxicity to the cells at higher concentrations. Cytotoxicity was reduced by prior treatment of the extract with polyvinylpolypyrrolidone, which was shown by thin layer chromatography to reduce the coumarin content.

Effects of hippocampal lesions on spatial delayed responses in dog.

Thirteen dogs were trained to perform spatial delayed responses to auditory cues in a three-choice Nencki testing apparatus with a delay of 0 s and then 10 s with a criterion of 90% correct responses in 90 consecutive trials. Then six dogs received bilateral surgical removal of the hippocampus via the cortex of the suprasylvian gyrus (without additional injury to the entorhinal and parahippocampal cortex). Three dogs received control surgical ablation of the suprasylvian gyrus, which was damaged in ablation of the hippocampus, and four dogs served as intact controls. After the surgery or rest period, the dogs were tested for their retention (10-s delay), and then they were given additional tests with extended delays (30, 60, and 120 s) and with distractions during the 60-s delay period. In comparison with both control groups, dogs with hippocampal ablations had moderately impaired postoperative retention, as evidenced by the elevated numbers of errors on criterion. In subsequent stages of testing with extended delays, the impairment was greater and was significantly correlated with the extent of injury to the hippocampus. These data, together with an analysis of the animals' responses to the three-choice situation, indicate that in dogs lesions of the hippocampus impair spatial memory.

The role of the inferior prefrontal convexity in performance of delayed nonmatching-to-sample.

Findings in an earlier study (Bachevalier, J. and Mishkin, M. Behav. Brain Res. 20, 249-261, 1986) indicated that ventromedial prefrontal cortex, which receives thalamic projections from the limbo-diencephalic system, is critical for visual recognition; whereas the dorsolateral prefrontal cortex, which receives no such thalamic projections, makes little or no contribution to this type of memory. In the present study, we examined the role in recognition of another prefrontal area outside the thalamic projection zone of the limbo-diencephalic system, namely, the inferior prefrontal convexity. In the first experiment, monkeys with lesions of this cortex (Group IC) were found to be impaired in relearning delayed nonmatching-to-sample (DNMS), but not on the subsequent DNMS performance test in which memory demands were greatly increased. In a second experiment, monkeys with combined lesions of the inferior and dorsolateral prefrontal cortex (Group LAT) were also found to be impaired in relearning DNMS, but in this case they were impaired, in addition, on the subsequent performance test. Neither group (IC or LAT) showed retardation in acquiring visual discrimination habits. Analysis of the DNMS behavior of both groups suggested that their deficits on this task were due not to a loss in recognition memory, but to various forms of perseverative interference. The results support the view that the inferior prefrontal convexity, like the dorsolateral prefrontal cortex, lies outside the limbo-diencephalic memory system not only anatomically but also functionally.

Influence of the varieties of differentiation training and prefrontal lesions on retention and reversal learning of avoidance responding in dogs.

The postoperative retention and reversal of go, no-go avoidance reflex differentiation with symmetrical and asymmetrical reinforcement were studied in dogs with prefrontal lesions and unoperated controls. The general pattern of the influence of such experimental variables as type of differentiation task an,d quality and arrangement of conditioned stimuli' was similar to that oberved preoperatively. However, prefrontal surgery changed the interactions between these experimental variables. The modifying role of the medial and the lateral parts of prefrontal cortex on the retention of differentiation and on reversal learning is discussed.

Stimulus control of instrumental reflexes in dogs: a comparison of alimentary and avoidance behaviors after prefrontal damage.

Two experiments involving parallel procedures to investigate stimulus generalization in prefrontal dogs under alimentary and defensive reinforcement were compared. Twelve dogs in the alimentary study were trained on a 50 percent partial reinforcement schedule, and 24 dogs were trained to avoid shock with either continuous shock availability and response contingent CS termination or with only 50 percent partial shock availability and response independent CS termination. One third of the subjects received bilateral medial prefrontal lesions, 12 dogs were given bilateral lesions of the lateral prefrontal cortex and the remaining subjects served as nonoperated controls. Generalization along the frequency dimension of the tonal CS was assessed during a sampling procedure within normal acquisition training, during complete extinction and following differentiation training. The results indicate specific effects from both the quality and the contingency of reinforcement. Within the limits of each reinforcement treatment, a dissociation occurred such that medial subjects tended to show heightened sensitivity to reinforcement density, while lateral subjects showed characteristic elevated reactivity during all generalization tests.

The role of contextual and sporadic stimuli in escape conditioning in dogs.

Instrumental escape bar-pressing responses were rapidly acquired in four male dogs and showed great resistance despite a long pause in experimental sessions. More intertrial responses were performed after short- than after long-latency escape responses. In the next stage of the experiment shock trials were discontinued and on the defensive context novel accoustical stimuli were introduced. The auditory stimuli provoked instrumental bar-press responses that were somewhat dependent on the intensity of stimuli.

Differentiation learning and auditory generalization in normal and prefrontal dogs after extensive avoidance training.

The continuation of a study of 24 dogs in the stages of avoidance reacquisition, differentiation training and generalization testing is reported. Subjects had previously received avoidance training with either response contingent CS termination on all trials or on only 50 percent of the training trials, prior to the administration of medial or lateral prefrontal lesions in 16 subjects. The remaining 8 subjects served as nonoperated controls. Following the appropriate surgical treatment, subjects were tested twice for generalization along the tonal frequency dimension of the avoidance CS. Trials to reacquisition criterion were comparable among all dogs, and subjects trained earlier with continuous response contingent CS termination had overlall faster response latencies, except for the medial subject that were slower than subjects trained under the partial schedule. Differentiation performance tended to show more success in the group given the earlier continuous response contingent avoidance training, although data from both training groups were variable. Subjects trained with the partial schedule had more extra- and intertial responses, which are considered as a byproduct of residual fear. Systematic effects from the surgical treatments were not found during differentiation training. Stimulus control by tonal frequency was more pronounced in subjects that had received the partial training schedule, and frequency generalization was disrupted by the lesion effects. The data are considered in light of reinforcement determinates from CS prolongation in the modification of defensive reflex control.

Avoidance responding in dogs trained in symmetrical or asymmetrical go, no-go differentiation.

The acquisition and the consolidation processes of avoidance responding in go, no-go differentiation with asymmetrical and symmetrical reinforcement procedures were studied in 49 male mongrel dogs. Differentiation training procedures with asymmetrical and symmetrical reinforcement were contrasted by the occurrence of painful shock on negative trials. The quality of conditioned stimuli and their relative saliency exerted strong effects on the rapidity of learning and the number of commision errors when the "asymmetrical" procedure was used, whereas these effects were strongly attenuated under "symmetrical" procedure of reinforcement. Dogs trained in "symmetrical" go, no-go differentiation showed characteristic responses executed with shorter latencies and larger percentages of errors on negative trials and numerous extra-and intertrial responding in early stages of differentiation learning. Retention tests showed a greater stability of acquired differential responding trained under "symmetrical" than under "asymmetrical" procedure of reinforcement. The data indicate that the strength of the secondary punishing effect of CS ;prolongation is directly related to the saliency of the stimulus. The relations between the primary and secondary punishing effects in the two types of differentiation task, and problem of signalling and arousing properties of stimuli used in training, were discussed.