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J Bures

Publications and source records attributed to J Bures.

At least 163 records · Page 9Linked to original sources
PubMed1986

Operant slowing of the extension phase of the reaching movement in rats.

Motor learning was studied in rats (n = 8) trained to slow down the forepaw extension while reaching into a narrow tube equipped with an axially moving piston. The photoelectrically monitored velocity of the movement between points P1, P2 and P3 (13.0, 15.1 and 17.3 mm from tube entrance) was evaluated with a laboratory computer which also plotted distributions of the corresponding time intervals and delivered food pellets whenever the time interval between P1 and P2 exceeded a preset threshold value (Group I). The additional condition of attaining P3 was required in Group II. Marked prolongation of the P1-P2 interval required about 20 sessions of 512 reaches in Group I and 27 to 30 sessions in Group II. The rats prolonged the P1-P2 interval in two ways: (a) By generating movements the amplitude of which oscillated around the P2 level and thus exposed the P2 sensor to the slow terminal part of the movement; (b) By true velocity decrease in the middle part (P1-P2) of the movements attaining the level P3. It is concluded that reaching is a highly stereotyped instrumental reaction, the pattern of which is not easily modified by operant conditioning. Substantial slowing (2 times) of the ballistic extension phase of long reaches probably reflects programmed coactivation of the antagonist.

Animals↗
PubMed1986

Influence of electroconvulsive shock and naloxone on acquisition and retention of a spatial navigation task in rats.

The effects of electroconvulsive shock (ECS) on learning and memory were examined in rats using the Morris navigation task. Rats were trained to escape from a large pool of water onto an invisible underwater platform. Application of ECS at various intervals before training (15 to 120 min) induced a significant time-dependent impairment of the acquisition of escape behavior; naloxone (1 mg/kg IP 15 min before ECS) did not prevent the ECS-induced impairment. One single active escape trial preceding ECS prevented ECS-interference with the subsequent acquisition of the task. Spatial navigation in well trained animals was significantly impaired 30 and 60 min after ECS. It is concluded that ECS disturbs the disturbs the formation of a spatial memory trace more than the retrieval of a previously formed spatial trace. Release of opioid peptides do not seem to contribute substantially to the amnesic effects of ECS in the spatial navigation task.

Animals↗
PubMed1986

Differential effects of cholinergic blockade on performance of rats in the water tank navigation task and in a radial water maze.

The disruptive effect of cholinergic blockade was tested under conditions in which either the working memory or the spatial mapping requirements of the behavioral task were emphasized. In Experiment 1, 13 rats were trained in an eight-arm radial water maze to asymptotic performance. When delays of 5, 10, 20, and 40 min were inserted between Choice 4 and Choice 5, incidence of errors in Choices 5-8 increased after pretrial (20 min) scopolamine injection (0.2 mg/kg, ip) faster than under control conditions and approached chance level with the 40-min delay. Scopolamine after Choice 4 or pretrial methylscopolamine was ineffective. In Experiment 2, 30 rats were trained in a Morris water tank. Acquisition was impaired by pretrial injection (20 min) of 0.1 and 0.2 mg/kg scopolamine, but a higher dose (1.0 mg/kg) was required to impair overtrained performance. In a working memory version of the navigation task, scopolamine administered 20 min before the first trial deteriorated retention tested 40 min later at a dose of 1.0 but not at 0.4 and 0.2 mg/kg. It is concluded that the disruptive effect of scopolamine is proportional to the demands on the working memory component of the task whereas the use of an overtrained mapping strategy is relatively resistant to cholinergic blockade.

Animals↗
PubMed1986

Colicinogeny in chronic inflammatory bowel disease.

There are several indirect arguments for a possible role of colicins in chronic inflammatory bowel disease (IBD). Colicinogeny was therefore investigated in 54 patients with ulcerative colitis, 39 patients with Crohn's disease, and 160 clinically healthy controls. No significant difference was found among the examined groups. The leukocyte migration inhibition test (with colicins as antigens) was performed to estimate cellular hypersensitivity to colicins. Migration indices not exceeding the normal range in controls contrasted with abnormal values found in 36% of ulcerative colitis and 80% of Crohn's disease patients. The results are believed to be proof of cellular hypersensitivity of IBD patients to colicins of their own Escherichia coli strains. The importance of this finding must be further clarified.

Adult↗
PubMed1986

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.

Animals↗
PubMed1986

Colicinogeny in colorectal cancer.

Colicins, bacteriocins of Escherichia coli and related bacteria of Enterobacteriaceae family, form a very heterogeneous group of antibiotically active substances of proteinaceous material. Antitumorous effect of colicins have also been demonstrated experimentally. The large bowel has been found to be a site of their native action. Therefore, our work has been aimed at investigating colicinogenicity in patients with colorectal carcinoma. From a total number of 77 patients with colorectal carcinoma, colicinogenic Escherichia coli was found in 32 persons (41.6%), whereas from a total of 160 control clinically healthy persons, colicinogenic Escherichia coli was found in 102 persons (63.8%). The difference is statistically significant (p less than 0.05). The absence of colicinogenic Escherichia coli may be one of the factors contributing to the origin and development of colorectal carcinoma in some of the patients studied. Studies of patients with adenomatous polyps, members of colon cancer families, and large prospective studies of the general population will be necessary to prove this hypothesis.

Adult↗
PubMed1985

Unilateral and bilateral cortical spreading depression interferes with radial maze performance in rats.

Seven rats with implanted cortical electrodes were trained in a 12-arm radial maze to asymptomatic performance (1.38 errors per trial). Single waves of cortical spreading depression (CSD) were elicited by application of cathodal current to the parieto-occipital cortex and monitored by suppression of callosal responses in the frontal cortex. Bilateral CSD elicited before the trial caused a small increase of error incidence in choices 1-6 but did not affect accuracy of choices 7-12. Bilateral CSD between choices 6 and 7 increased error incidence in the second half of the trial from 1.33 to 2.84, i.e. almost to the chance level of 3.0. Unilateral CSDs elicited before the first half of the trial in one hemisphere and in the same or in the contralateral hemisphere before the second half of the trial caused similar deterioration of performance in choices 7-12 (2.4 and 2.1 errors, respectively). It is concluded that the CSD effects have both proactive and retroactive components and that the working memory record is not lateralized at the cortical level.

Animals↗
PubMed1985

A response-specific conditioned aversion to rewarding hypothalamic stimulation in rats.

Rats with hypothalamic electrodes were trained to self-stimulate by nose-poking and by licking at a dry spout. Separate groups of animals were then exposed to pairings of either self-stimulation by licking or by nose-poking with the subsequent administration of LiCl. The licking/LiCl pairing group exhibited a marked attenuation of licking maintained by hypothalamic stimulation on the first retention trial (24 h post LiCl). This effect was enhanced by a further licking/LiCl pairing. In a final cross-over trial with this group, nose-poking maintained by stimulation at the same site and intensity was found to be unaffected. With another group of animals nose-poking/LiCl pairing had no effect on self-stimulation, despite two conditioning trials. In a final cross-over trial with this group licking maintained by stimulation of the same site and intensity was also unaffected. These data indicate that the sensory properties of brain stimulation may be dependent on the behavioural context in which the stimulation occurs.

Animals↗
PubMed1985

Post-trial flicker stimulation interferes with spatial memory in the Morris water maze.

Rats (n = 20) trained under monocular viewing conditions in the working memory version of Morris water maze task received daily a single acquisition trial with a new location of the invisible escape platform followed after 15 min by a single retrieval trial. Escape latency decreased by 50% during retrieval. Flash stimulation (20 Hz, 0.6 J) during the entire 15-min delay disrupted retention, but this effect was not observed when the flashes started 3 or 5 min after acquisition. It is concluded that successful place learning requires a brief interference-free post-acquisition interval.

Animals↗
PubMed1985

D-ala2-Metenkephalinamide blocks the synaptically elicited cortical spreading depression in rats.

Spreading depression (SD) was elicited in rats anesthetized with pentobarbital by a train of 8 electrical pulses (0.1 ms, 10 Hz) applied to parietal cortex. Local application of 50 micrograms of D-ala2-metenkephalinamide (DAME) on the stimulated area evoked one or two SD waves followed by an increase of SD threshold from 40 V to 90 V. This effect could be partly prevented by naloxone (1 mg/kg i.p.) and reversed by local application of 4-aminopyridine (10(-3) M, 2 microliters), which reduced SD threshold to 5 and 20 V in normal and DAME-treated cortex, respectively. It is argued that DAME exerts an inhibitory effect on cortical neurons and that the initial SD facilitation is due to initial blockade of inhibitory neurons in the superficial cortical layers.

Aminopyridines↗
PubMed1985

Operant control of the pattern of licking in rats.

In an attempt to slow down the highly regular rate of licking by instrumental conditioning, 10 rats were trained to obtain their daily ration of water in an apparatus equipped with a retractable drinking spout. Termination of a photoelectrically monitored lick started a computer controlled delay during which the spout was made inaccesible. The subsequent return of the spout was either permanent or limited to a time window (D or W conditions). The cycle was reset by each lick. With stationary spout, the interlick intervals (ILIs) were around 210 +/- 16 ms (median and interquartile range). The spout return was gradually delayed during 22 sessions from 140 to 260 ms and limited to a 260-340 ms window during 11 sessions. A session consisted of 512 licks with stationary spout followed by 7 X 512 licks under D or W conditions. Two rats were able to smoothly adjust to the limited spout availability by increasing median ILI to 290 ms. Four rats generated bimodal ILI distributions indicating gradual reduction of tongue protrusion to an undetected lick followed by abrupt increase of lick amplitude. Three rats increased the median ILI to 260 ms and the interquartile range to 80-150 ms. The above changes of lick pattern allowed the rats to attain tongue-spout contact in 41 to 89% licks. It is concluded that the rats can substantially slow down their lick rate provided that they receive feedback information about the failure or success of each lick.

Animals↗
PubMed1985

Threshold of synaptically elicited cortical spreading depression: drug-induced changes in rats.

The role played by synaptic phenomena in the initiation of Leão's spreading depression (SD) was examined in 30 rats anaesthetized with pentobarbital. SD was elicited by a train of 8 electrical pulses (0.1-0.3 msec, 10 Hz) applied through bipolar electrodes to the exposed cortical surface. The slow potential waves of SD were recorded from the stimulated site and from a remote cortical area. Threshold stimulus intensity (40 V) was increased above 80 V when low frequency stimulation (0.3 Hz, 10 V) was applied through the same electrodes. SD penetration into the stimulated area was blocked with higher stimulus rates (3-10 Hz) and intensities (20 V). Systemic application of the pyrrolopyrimidine drug BE 58-271 decreased SD threshold from 40 V to 7 V and reduced also the intensity and frequency of stimulation inducing the SD blockade. Similar effects were obtained with local application of 2 microliters of 10(-3) M 4-amino-pyridine to the stimulated cortex. The SD threshold was reduced from 40 V to 5 V, probably by prolonged depolarization of axon terminals and increased output of transmitters. Estimation of SD threshold revealed a biphasic effect of locally applied penicillin: an initial threshold decrease which gradually changed with the development of regular interictal discharge into a threshold increase and eventual SD blockade. It is concluded that sudden synaptic activation of cerebral cortex elicits SD whereas prolonged continuous stimulation decreases SD susceptibility, probably by enhancing the K+ clearance.

4-Aminopyridine↗
PubMed1985

Radial maze in the water tank: an aversively motivated spatial working memory task.

An 8-arm radial maze with 40 X 40 X 12 cm channels was inserted into a circular tank (120 cm in diameter, 60 cm high) filled 30 cm deep with 25 degrees C opaque water. Rats (n = 13) had to escape from the central area of the maze (30 cm in diameter) onto an invisible bench (1 cm below water surface) at the far end of each channel. Twenty sec after each choice the bench was collapsed and the animal was forced to choose again until all 8 channels had been visited. From the very beginning rats performed better than chance. The acquisition and performance of this aversively motivated radial maze test is similar as in conventional elevated 8-arm radial mazes.

Animals↗
PubMed1985

Lateralized rewarding brain stimulation affects forepaw preference in rats.

Rats trained to reach for food pellets into a narrow tubular feeder consistently prefer to perform this stereotype instrumental movement with either the left or right forepaw. In 16 rats with established handedness electrodes were implanted into both lateral hypothalami. The animals were rewarded by intracranial self stimulation (ICSS, 300 msec, 50 Hz, 20-60 microA) for reaching into a modified feeder for a plastic ball operandum, the movement of which between the bottom and entrance of the feeder was monitored by mechanical contacts. The rats readily continued to reach when ICSS was delivered immediately after the photoelectrically detected reach or after the displacement of the operandum. Most rats learned in a single session to modify the movement when ICSS delivery was made contingent upon holding the operandum between the bottom and entrance of the feeder for 256 or 512 msec. The efficiency of reaching (ratio of successful reaches to all reaches) decreased with increasing holding time; only a few animals were able to master a 1024 msec delay. Reaching was supported by ICSS of either lateral hypothalamus. Whereas in 8 rats the strongly expressed forepaw preference was not changed by lateralized ICSS, in 8 latently ambidextrous animals stimulation of the lateral hypothalamus ipsilateral to the preferred forepaw increased reaching with the normally non-preferred forepaw from 15% to 60%. Stimulation of the lateral hypothalamus contralateral to the preferred forepaw did not change the preference. The preference shift was equally well expressed in simple and difficult versions of the task. It is concluded that lateralization of motivational influences can be reflected in the asymmetry of the neural mechanisms processing the lateralized sensory signals and/or elaborating the lateralized motor output.

Animals↗
PubMed1985

On-demand platform improves accuracy of the Morris water maze procedure.

In order to prevent chance finding of the hidden target in the Morris water tank task, the rigid underwater platform is replaced with a collapsible platform, resting at the bottom of the pool. A computerized videosystem tracks the rat's movement across the pool and raises the platform when the animal has stayed in the target area for a predetermined time. Acquisition of the task with the collapsible platform proceeds at a similar rate as with the rigid platform when the criterion conditions are easy (target distance 15 cm, target time 2.5 s), but gradually deteriorates when the target time increases to 10.0 s. Successful solution of the modified task requires accurate localization of the target under open loop conditions and is thus well suited for investigation of the fine structure of the cognitive maps and of their changes induced by lesions or drugs.

Animals↗
PubMed1985

Persistence of working memory of rats in an aversively motivated radial maze task.

The effects of various within-trial delays on the performance of rats in an 8-arm radial water maze (RWM) were investigated. Rats (n = 13) were trained to escape from 25 degrees C opaque water onto a submerged bench situated at the far end of each channel of the maze. After 20 s the chosen bench was collapsed and the rat had to return to a central platform, 1 cm above water level. After 15 s the platform was lowered and the animal was forced to choose again. This was repeated until all 8 channels had been visited. After 30 daily trials the mean number of correct choices per trial (first 8 choices) was 7.8. In Experiment 1, delays from 40 min up to 21 h were inserted between choices 4 and 5. The number of revisited channels (errors) in the second half of a trial increased rapidly with the duration of the delay, and was not significantly different from chance at 640 min. In Experiment 2, delays of 2.5, 5, 10 or 20 min were inserted between individual choices. Again, performance deteriorated with the duration of the delay. When the incidence of errorless trials was analyzed, performance was not significantly different from random at 5 min inter-choice delays. Comparison with conventional radial maze studies indicates that spatial working memory in the RWM has a slower, but also exponential decay.

Animals↗
PubMed1985

Transplantation of brain tissue. Substantiation of a collaborative research project.

Recent research into the transplantation of foetal cerebral tissue into the brains of adult mammals is reviewed. Functional integration of the graft with the host CNS makes it possible to form new intercentral connections and heterotopic sensory inputs, to replace lost neuroendocrine or modulatory influences and to produce brains with unusual functional properties. The potential significance of the transplantation studies for the therapy of traumatic or degenerative brain lesions calls for international coordination of these multidisciplinary research projects.

Animals↗