Effect of vibrissae removal on the defensive behavior of rats in early ontogeny

Influence of restricted sensory afferentation in rats forming of defensive reactions was studied by vibrissectomy from 9 to 20 day of postnatal ontogeny. Defensive withdrawal reaction in response to touch from 10 to 18 day, duration of freezing on 20 day, "open field" behavior on 25 day were measured. Intensity of withdrawal reactions, freezing duration, flight reaction and emotionality in "open field" were lower in vibrissectomized rats with comparison to control.     

Use of spatial information and search strategies in a water maze analog in Drosophila melanogaster

Learning the spatial organization of the environment is crucial to fitness in most animal species. Understanding proximate and ultimate factors underpinning spatial memory is thus a major goal in the study of animal behavior. Despite considerable interest in various aspects of its behavior and biology, the model species Drosophila melanogaster lacks a standardized apparatus to investigate spatial learning and memory. We propose here a novel apparatus, the heat maze, conceptually based on the Morris water maze used in rodents. Using the heat maze, we demonstrate that D. melanogaster flies are able to use either proximal or distal visual cues to increase their performance in navigating to a safe zone. We also show that flies are actively using the orientation of distal visual cues when relevant in targeting the safe zone, i.e., Drosophila display spatial learning. Parameter-based classification of search strategies demonstrated the progressive use of spatially precise search strategies during learning. We discuss the opportunity to unravel the mechanistic and evolutionary bases of spatial learning in Drosophila using the heat maze.     

Effect of circadian phase on performance of rats in the Morris water maze task

The authors examined spatial working memory in the Morris water maze during the activity and rest periods of Wistar rats. Wheel-running activity was measured continuously as a marker of circadian phase. To minimize possible masking effects on performance, animals were placed in constant dim light the day before testing and tested in similar light conditions. Three experiments were run, each of them using animals varying in their previous experience in the water maze. Half of the animals of each experiment were tested 2 to 3 h after activity onset (active group), and the other half were tested 14 to 15 h after activity onset (inactive group). In the three experiments, a significant phase effect was observed in the animals' performance in the water maze; animals tested in the active phase showed steeper acquisition curves. These phase effects on performance are due to the animals' search pattern and not to a better acquisition and maintenance of spatial information; rats tested in the inactive phase found the platform faster on the first trial of the test, when the information on the location of the platform had not been presented to the animals. This effect vanished as the amount of training in the pool increased. Finally, swimming speed also showed a temporal effect, suggesting the existence of a phase effect for motivation to escape from the water; rats tested during their inactive phase tended to swim faster. All together, the data suggest a modulating effect of the biological clock on performance in the water maze, particularly when the animals are less experienced.     

Effect of L-asparaginase on retention of maze learning in mice

Long-term memory impairment has been described previously in mice receiving inhibitors of protein synthesis. In the present work, the enzyme L-asparaginase was injected into mice by an intrathecal or by an intraperitoneal route and produced a significant impairment of memory. Glutamine and asparagine prevented the effect of asparaginase when injected by the intraperitoneal route.     

Effect of relative humidity on the movement of rat vibrissae in a 60-Hz electric field

The snouts of rats were placed in a 60-Hz electric field at an unperturbed field strength of 50 kV/m. A count of the number of vibrissae that moved in the field was made on a series of rats over a number of days where the laboratory humidity varied from 25% to 48%. The number observed to vibrate fell from nine to zero or one at relative humidities between 25% and 39%, respectively.     

Hairs and vibrissae in the Rhinocerotidae

Evidence is reviewed and observations are submitted concerning the occurrence and distribution of body hair in rhinoceroses. Absence of externally visible hair is shown to be not necessarily indicative of absence of hair follicles and to be part of a morphological cooling mechanism necessitated by the dynamics of the large body. Eyelashes are shown to be present on the lower eyelid of three species at least. The post-natal absence of all groups of facial vibrissae is confirmed for all rhinoceros forms, but a genal vibrissa is recorded for a Diceros foetus. Observations are submitted upon the hitherto undescribed histology of Diceros skin.     

Effects of physical fatigue in mice on learning performance in a water maze

We investigated the effects of physical fatigue produced by swimming exercise on learning the Morris water maze in BALB/c mice. We measured the escape latency in the maze immediately after the swimming exercise. The control group was soaked in the water but not fatigued. For easier tasks, like one with an obvious cue flag, the escape latency was not changed by exercise fatigue. However, escape latency was increased after exercise fatigue for more difficult tasks of spatial learning. These results appear to suggest that physical fatigue impaired learning performance. The effects of swimming exercise fatigue on learning efficiency were then investigated. Mice were continuously fatigued during the spatial learning period. This increased escape latency between the first and third sessions. The results suggest that learning efficiency was impaired by exercise fatigue. This system may be useful for screening new foods used to enhance brain function during exercise.     

Neonatal exposure to intermittent hypoxia enhances mice performance in water maze and 8-arm radial maze tasks

Hypoxia has generally been reported to impair learning and memory. Here we established a hypoxia-enhanced model. Intermittent hypoxia (IH) was simulated at 2 km (16.0% O2) or 5 km (10.8% O2) in a hypobaric chamber for 4 h/day from birth to 1, 2, 3, or 4 week(s), respectively. Spatial learning and memory ability was tested in the Morris water maze (MWM) task at ages of postnatal day 36 (P36)-P40 and P85-89, respectively, and in the 8-arm maze task at P60-68. The long-term potentiation (LTP), synaptic density, and phosphorylated cAMP-responsive element-binding protein (p-CREB) level in the hippocampus were measured in mice at P36 under the IH for 4 weeks (IH-4w). The results showed that IH for 3 weeks (IH-3w) and IH-4w at 2 km significantly reduced the escape latencies of mice at P36-40 in the MWM task with significantly enhanced retention, and this spatial enhancement was further confirmed by the 8-arm maze test in mice at P60-68. The improvement in MWM induced by IH-4w at 2 km was still maintained in mice at P85-89. IH-4w at 2 or 5 km significantly increased amplitude of LTP, the number of synapse, and the p-CREB level in the hippocampus of P36 mice. These results indicated that IH (4 h/day) exposure to neonatal mice at 2 km for 3 or 4 weeks enhanced mice spatial learning and memory, which was related to the increased p-CREB, LTP, and synapses of hippocampus in this model.     

Modified water maze for studying spatial memory of rats

A method for evaluation of impairments of spatial memory in rats is put forward. Sensitivity of the advanced method based on the principles of Morris' water maze was compared with that of the classic prototype. Efficiency of the advanced method was assessed by dose- and time-dependent effects of agroclavine on the spatial memory of rats. Agroclavine (10 micrograms/kg) was shown to produce spatial memory impairment in rats. The obtained results also indicate that the modernized maze is more sensitive in revealing impairments of the spatial memory in rats than the classic water maze.     

Comparative accuracy of methods for protein sequence similarity search

MOTIVATION: Searching a protein sequence database for homologs is a powerful tool for discovering the structure and function of a sequence. Two new methods for searching sequence databases have recently been described: Probabilistic Smith-Waterman (PSW), which is based on Hidden Markov models for a single sequence using a standard scoring matrix, and a new version of BLAST (WU-BLAST2), which uses Sum statistics for gapped alignments. RESULTS: This paper compares and contrasts the effectiveness of these methods with three older methods (Smith- Waterman: SSEARCH, FASTA and BLASTP). The analysis indicates that the new methods are useful, and often offer improved accuracy. These tools are compared using a curated (by Bill Pearson) version of the annotated portion of PIR 39. Three different statistical criteria are utilized: equivalence number, minimum errors and the receiver operating characteristic. For complete-length protein query sequences from large families, PSW's accuracy is superior to that of the other methods, but its accuracy is poor when used with partial-length query sequences. False negatives are twice as common as false positives irrespective of the search methods if a family-specific threshold score that minimizes the total number of errors (i.e. the most favorable threshold score possible) is used. Thus, sensitivity, not selectivity, is the major problem. Among the analyzed methods using default parameters, the best accuracy was obtained from SSEARCH and PSW for complete-length proteins, and the two BLAST programs, plus SSEARCH, for partial-length proteins.      

Strain-independent global effect of hippocampal proteins in mice trained in the Morris water maze

A series of individual proteins have been linked to performance in the Morris water maze (MWM) but no global effects have been reported. It was therefore the aim of the study to show which proteins were strain-independent, global factors for training in the MWM. Strains C57BL/6J, apodemus sylvaticus and PWD/PhJ were used. MWM and gels from trained animals were from a previous own study and corresponding yoked groups were generated. Hippocampal proteins were extracted and run on two-dimensional gel electrophoresis. Spots with different expressional levels between trained and yoked groups were punched and identified by mass spectrometry (nano-LC-ESI-MS/MS, ion trap). Two-way ANOVA with two factors (strain and training) was carried out and a Bonferroni test was used to compare groups. 12 proteins from several pathways and cascades showed different levels in trained mice versus corresponding yoked animals in all strains tested. Four out of these proteins were verified by immunoblotting: beta-synuclein, profilin 2, nucleoside diphosphate kinase A (NME1) and isocitrate dehydrogenase 3. Four proteins verified by immunoblotting could be shown to be involved in training in the MWM as a global effect, independent of the strain tested.     

Reward type influences performance and search structure of an omnivorous bird in an open-field maze

Open-field mazes are routinely used to study the spatial cognitive abilities of birds and are often implicitly assumed to be suitable tests of generic spatial memory ability. In recent years there has been extensive research motivated by considerations of an animals’ ecology, demonstrating potential examples of specialisations of spatial cognition, as a result of foraging niche. The study reported here demonstrates differences in maze performance as a function of reward type (nectar and invertebrates) that can be predicted from the natural distributions of these rewards. As well as specific implications for the nature of spatial memory specialisation in this species, the results hold more general implications for the use of open-field mazes as tools for measuring and comparing spatial memory ability between species.     

The effect of binocular and monocular viewing conditions on performance of rats in the Morris water maze

The visually guided behaviour in the Morris water maze (using distal extramaze cues for navigation to a small invisible platform in a large pool of opaque water) was analyzed by comparing monocular and binocular performance of hooded rats in various versions of this task. A dish-shaped metal foil occluder connected to a carrier fixed to the frontal bones was used to restrict vision to one eye. Acquisition of the water maze task with one eye occluded proceeded at the same rate as with both eyes open. There was no difference in the transfer from binocular to monocular and from monocular to binocular viewing. Retrieval of the monocularly acquired habit was equally efficient with the same as with the contralateral eye. Similar results were obtained in naive and overtrained rats. In the working memory version of the task, rats received a single acquisition trial with a new position of the escape platform followed after a delay of 2, 5, 20 or 40 min by a single retrieval trial. Performance deteriorated with increasing delay faster under interocular transfer conditions then when the same eye was used in both trials. No signs of ocular dominance were found in this task. It is concluded that successful place learning is little affected by monocular or binocular viewing conditions, but that monocular impairment becomes apparent when the difficulty of the task is increased.     

Effect of ppGpp on the accuracy of protein biosynthesis

The maintenance of accuracy in protein biosynthesis in amino acid-starved rel+ strains of Escherichia coli has been attributed to an effect of ppGpp on the accuracy of aa-tRNA selection by the ribosome. It has been determined that concentrations of ppGpp characteristic of those found in amino acid-starved cells have no effect on the rate of reaction of poly(U)-programmed ribosomes with either the cognate (Phe) or the near-cognate (Leu2) ternary complexes. Neither the rate of GTP hydrolysis, which signals selection of the ternary complex, nor the rate of peptide formation, which signals the acceptance of the aa-tRNA after proofreading, is affected by the nucleotide. The results indicate that the effect of ppGpp in maintaining the accuracy of protein biosynthesis in cells starved for an amino acid is not due to a direct effect on the rate constants for substrate selection by the ribosome.     

The experience in the water maze task can affect the circadian rhythm of locomotor activity

Wistar rats maintained in cages with running wheels and submitted to a skeleton photoperiod or to a light - dark cycle were tested in the Morris water maze. Half of the animals were exposed to the task during their active phase while the other half was exposed during their inactive phase. The effect of the experience in the water maze, a strong arousing event, on the rhythm of wheel-running activity was evaluated. In the first experiment, a group of animals submitted to a skeleton photoperiod was trained every day in the reference memory version of the task. The novel experience in the water maze had a strong phase-dependent masking effect: it produced an intense post-training bout of activity in the animals tested during their inactive phase. Another experiment was run using single working memory sessions in the water maze and with animals submitted to a light - dark cycle. The circadian rhythm of locomotor activity was evaluated on undisturbed days and compared with testing days. The experience in the water maze produced a significant increase in variability of activity onset during both circadian phases. Taken together, the data suggest that there is a modulating effect of the arousing experience in the pool on the overt circadian rhythm of locomotor activity.