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Biomedical subjects

I Krekule

Publications and source records attributed to I Krekule.

At least 19 recordsLinked to original sources
PubMed1992

Immunofluorescence detection of the vimentin epitope in chromatin structures of cell nuclei and chromosomes.

We describe immunofluorescence detection of the vimentin epitope, recognized by monoclonal antibody VI-01, in chromatin structures of eukaryotic cell nuclei and chromosomes. The approach used is based on increased sensitivity of 5-bromodeoxyuridine (BrdU)-substituted DNA to UV irradiation-induced crosslinking of DNA with proteins in vivo, by which the proteins interacting with chromosomal DNA can be immunovisualized in situ.

Animals↗
PubMed1991

[Imaging and computer processing of the ocular fundus picture].

Computer analysis of a picture in ophthalmology makes objective evaluation of the clinical finding possible. After analogue-digital transfer the pictures of the fundus on a black and white negative and coloured positive 24 x 36 mm were analyzed on a Pericolor 2000 E computer. We measured the area of the glaucoma excavation of the papilla of the optic nerve, calculated the C/D ratio, assessed changes in the picture of the fundus in exudative diabetic maculopathy on paired slides obtained after a one-year interval. We evaluated changes of fluorescein penetration during fluoroangiography in different diseases.

Fluorescein Angiography↗
PubMed1989

Image analysis of transparent particle systems by mathematical morphology methods.

The particle images are often distorted by apparent holes due to undeflected transmitted light. These apparent holes must be disregarded for a consequent image analysis. The reconstruction of the real particles by methods of mathematical morphology was used. The problems associated with touching particles were also dealt with. The method is illustrated on an ion-exchanger system.

Algorithms↗
PubMed1988

Does nondirectional signalization of target distance contribute to navigation in the Morris water maze?

The possibility that rats can navigate in the Morris water maze by reducing the difference between the memorized platform scene and the current sensory input was tested in nine blind rats. A computerized videosystem monitored the rats' movements in the pool and converted the rat-target distance into tones the frequency of which increased in 64 equal steps from 120 Hz at 128 cm to 7680 Hz at 0 cm. During 15 days of training to find a fixed platform position from different starting points (12 trials per day) average escape latencies decreased from 39.0 to 25.4 s. The performance significantly deteriorated when the acoustic distance signalization was omitted and/or when the target position was changed form trial to trial. It is concluded that blind rats solved the task by simultaneously employing search strategy based on position responses, mapping using acoustic background beacons, and distance reduction navigation. It is argued that the various strategies are additive and that their relative significance depends of the conditions of the experiment.

Acoustic Stimulation↗
PubMed1985

Quantitative evaluation of electromyogram activity in rat extensor and flexor muscles immobilized at different lengths.

Because immobilization of muscles in the "long" position mitigates the effects of inactivity and rapid wasting occurs when muscles are immobilized in the "short" position, a study was made of the EMG activity in the soleus (SOL)--an extensor muscle--and the tibialis anterior (TA)--a flexor muscle--in order to clarify the possible role of muscle function in modifying the course of disuse atrophy. EMG activity was recorded in the SOL and TA muscles in adult rats in which the ankle had been immobilized in a plaster cast either in plantar flexion or dorsiflexion. The number of action potentials per minute in samples of the EMG activity from control and immobilized muscles was assessed before, for 10 days during immobilization, and up to 9 days after removal of the cast. Immobilization in the short position (plantar flexion) led to a dramatic reduction in the EMG activity of the SOL (to 10% of the control). On the other hand, fixation of the SOL in the long position was without effect upon resting EMG activity. In the TA, EMG activity was exclusively phasic in character and corresponded to about 3% of that of the SOL. Neither the fixation of the ankle in plantar flexion nor dorsiflexion had any appreciable effect upon EMG activity in the TA. We conclude that, because immobilization in the lengthened position does not increase EMG activity in either extensor or flexor muscles, passive stretch appears to be the factor mainly responsible for mitigating the effects of disuse in this situation. On the other hand, when a typical extensor muscle (SOL) is immobilized in the shortened position and undergoes rapid wasting, an accessory role of decreased activity cannot be excluded.

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↗
PubMed1982

Pattern of labelling of the rat brain stem after intraventricular administration of 3H-leucine; low and high resolution autoradiographic study.

The pattern of labelling of proteins of the periventricular grey matter was studied two hours after intraventricular administration of 3H-leucine by low- and high-resolution autoradiography. The pattern was investigated by computer-controlled densitometry. The deposition of radioactive, proteins in the periventricular grey surrounding the mesencephalic part of the aquaeductus Sylvii was compared with that surrounding the fourth ventricle. In the former case, the distribution, of grains was in a circular area 500-600 micrometer in diameter; the densitometric tracing revealed a homogeneous distribution of the label; in the latter case, the distribution was nonhomogeneous and was limited by the tissue components forming the wall of the fourth ventricle. A comparison of the intensity of labelling (performed by a combination of low- and high-resolution autoradiography indicated: a) relatively substantial labelling of proteins of ependymal cells, b) very sparce labelling of subependymal layers, c) very high labelling ot neurones, adjacent to the subependymal layers. The significance of these findings for the interpretation of studies using the intraventricular administration of labelled amino acids for investigating brain macromolecular metabolism is discussed.

Animals↗
PubMed1979

Radial maze type as a determinant of the choice behavior of rats.

Spatial memory of rats was examined in two types of radial mazes in which animals had to obtain food from 6-, 8-, or 12-different arms without repeating choices. In Maze 1 with tubular channels closed at the far end rats returned to the central platform by backing out from the just visited alley. In Maze 2 the tubular channels were equipped with one-way doors at both ends and the central platform was raised 5 cm above the floor. Rats leaving the far end of the alley returned to the central platform through a circular hole in its center. Performance was almost perfect in both apparatuses, but rats preferred to enter adjacent alleys in Maze 1 and widely separated alleys in Maze 2. These behaviors were significantly different from computer-simulated random choice from the set of correct solutions of the task. It is concluded that Maze 2 is better suited for repeated experiments with the same animal because the obligatory return to the center of the platform precludes the simplification of the task by response chaining.

Animals↗
PubMed1978

Chronic polyelectromyography in awake, unrestrained animals.

A procedure is described for making an implantable electrode array for recording EMG activity in muscles of awake, unrestrained animals (rats and cats) at rest, during rhythmic activity and in response to various reflexogenic stimuli. The electrode array consists of a percutaneous connector (covered with Dow-Corning Silastic Medical Adhesive), steel wire spiral leads contained in silicone tubing and silicone plate probes with platinum electrodes. These plate probes can be fixed either to the bone underneath the muscle, slipped under the fascia, or fixed between muscles. EMG records are presented of postural activity and ambulation in rats, mastication in cats and unilateral and bilateral spinal and supraspinal reflex responses in rat hind limb muscles up to 6 months after implantation. The advantages (and drawbacks) of this technique and its possible uses in neurophysiology are enumerated in the discussion.

Animals↗
PubMed1976

Work-induced potassium changes in skeletal muscle and effluent venous blood assessed by liquid ion-exchanger microelectrodes.

Using liquid ion-exchanger semimicroelectrodes with a side pore, we measured changes of extracellular potassium concentration (Ke+) in adult rabbit and cat gastrocnemius muscles and in venous effluent blood flowing from the cat gastrocnemius muscle during various bouts of activity induced by sciatic nerve stimulation. 1. Isometric tetanic contractions (at 50 Hz) of various durations caused transient accumulation of Ke+ which was non-linearly related to the duration of muscle activity. The peak values of Ke+ in response to muscle stimulation were analogous in rabbits and cats, attaining values, e.g. after a 20-sisometric tetanus, between 8-9 mEq/1K+ in both species. 2. Potassium concentration in venous effleunt blood (K+ven) was transiently increased after isometric tetani. Since blood flow was measured at the same time, it was possible to calculate the amount of K+ lost by the muscle after tetani of various durations. A 32 g gastrocnemius muscle of the cat, for example, loses 9.36 +/- 1.52 muEqK+ after a 20-s isometric tetanus, which corresponds roughly to 0.5% of the total muscle potassium content. The loss of K+ in this muscle was 29.3 pEq K+ /impulse/100 g fresh muscle tissue. 3. There was no evident difference between the amount of K+ released during isometric tetani, or tetanic contractions performed under isotonic conditions. Single twitches evoked by indirect stimulation at 1 HZ for several minutes also induced a small rise in K+ven. 4. If the loss of K+ from the muscle into the blood stream is transiently prevented by arterio-venous occlusion installed immediately before a 10-s isometric tetanus, most K+ is released subsequently when blood flow is renewed, if the occlusion lasts for 20-25 s. It is not until blood flow is occuded for 40-60 s that most K+ is apparently resorbed and only a minor portion is released and is to be found in the venous blood. 5. The transient accumulation of muscle extra-cellular potassium may locally affect nerve endings, skeletal and smooth muscle cells.

Animals↗