Biomedical subjects

S Ribaric

Publications and source records attributed to S Ribaric.

16 recordsLinked to original sources

PubMed2005

Postural stability of Parkinson's disease patients is improved by decreasing rigidity.

Postural instability has a big impact on the quality of life of patients with Parkinson's disease (PD) as it often leads to an insecure stance and fall. We investigated if postural stability in these patients improves by decreasing rigidity with a dopaminergic agonist. In our study, we tested eight PD patients with no concomitant diseases. Their age was 61 +/- 2 years (mean +/- SE) and their Hoehn-Yahr score was 3 +/- 0.1. The patients were evaluated according to the Unified Parkinson's Disease Rating Scale for motor function (mUPDRS) and with stabilometric measurements of forward-backward and side-to-side body oscillations during free stance with eyes open. Both evaluations were performed in an "off "state and in an apomorphine-induced "on" state. As expected, the mUPDRS score was significantly decreased in the "on" state with posture being improved in six patients, gait in eight patients and postural stability in seven of eight patients. In addition, apomorphine caused a significant reduction of the relative amplitude of lower frequencies and an increase of the relative amplitude of higher frequencies of forward-backward body oscillations. The results of stabilometry and mUPDRS evaluations are in agreement with the effect of apomorphine on rigidity, indicating that postural stability of PD patients is improved by decreasing rigidity.

Antiparkinson Agents↗

PubMed2001

Selective stimulation of motor fibres in the sciatic nerve of a rat.

The aim of this study was to test the possibility of selective activation of slow and fast fibres within the rat tibialis anterior muscle, via selective stimulation of corresponding motor fibres within the sciatic nerve. For this purpose the implantable cuffs containing two and three platinum ring-electrodes were constructed and surgically fitted on the left and right sciatic nerve in five Wistar rats. In the left nerve, conventional, rectangular stimuli were delivered bipolarly via double-ring cuffs. In the right nerve quasitrapezoidal stimuli were delivered tripolarly via treblering cuffs. After 60 s of simultaneous and continuous stimulation of both nerves the left and right anterior tibialis muscle were isolated and immediately frozen in liquid nitrogen. Each muscle was completely cut in step serial sections. Glycogen depletion was demonstrated by Periodic acid-Schiff (PAS) reaction. In one randomly selected rat an immunohistochemical profile of muscle fibres (type I, IIA, IIB, and IIX) was determined with antibodies against myosin heavy chain isoforms. In other rats typing of glycogen depleted fibres was performed according to muscle fibre diameters. Preliminary results show that glycogen depleted fibres in the selected rat were type IIB fibres in both types of stimulation, except for a few type I fibres, stimulated by quasitrapezoidal impulses. In other rats glycogen depleted fibres were always the fibres of the largest diameter, most probably also type IIB fibres in both types of stimulation. Glycogen depletion of type I fibres was never observed in muscles stimulated by rectangular stimuli.

Animals↗

PubMed2001

Presentation of dermatological images on the Internet.

In this paper, we focused on selected problems of integrating and presenting medical images organised in a World Wide Web (WWW) database. To solve these problems we developed a prototype of a bilingual (Slovenian and English) WWW database of medical images for the field of dermatology. This dermatology database includes a graphic interface with four modes of access: (1) browsing, (2) searching, (3) comparison of images, and (4) self-testing. The quantity and quality of requests to this WWW database was estimated with log file analysis. There was a steady increase in the number of users and volume of data transferred from the dermatology WWW database.

Databases, Factual↗

PubMed2001

A Windows computer application for long term data acquisition, storage and presentation of biological signals.

We developed a windows application dedicated to recording, displaying and storing large amounts of biological signals on a standard PC. The application works in Matlab and uses an A/D-converter interface that enables a user to run the same software for signal acquisition, display and processing with different A/D-converter boards. The software program consists of three integrated modules, for setting the protocol for signal acquisition; for commands that can be accessed during data acquisition and for software routines that enable off-line viewing, pre-processing and processing of recorded data. It adapts to different computer hardware configurations by enabling the user to define file size, data resolution and file storage on local and network hard disks during signal acquisition.

Animals↗

PubMed2001

Three-dimensional study of the capillary supply of skeletal muscle fibres using confocal microscopy.

Three-dimensional (3D) study of capillary network of individual muscle fibres in rat extensor digitorum longus (EDL) and soleus (SOL) muscles is presented. Stereology and 3D reconstruction techniques were applied to stacks of serial optical sections recorded by a confocal microscope from thick muscle slices. The results suggest that SOL muscle fibres have a larger surface area and volume as well as a larger length of capillaries per fibre length than EDL. On the other hand, these two muscles have a similar ratio of capillary length to fibre surface area. The 3D approach to evaluation of muscle fibre capillarization brings many advantages over traditional measurements made on single muscle sections and could also be applied to the study of angiogenesis in other tissues.

Animals↗

PubMed2000

Reversible transitions between synchronization states of the cardiorespiratory system.

Phase synchronization between cardiac and respiratory oscillations is investigated during anesthesia in rats. Synchrograms and time evolution of synchronization indices are used to show that the system passes reversibly through a sequence of different phase-synchronized states as the anesthesia level changes, indicating that it can undergo phase transitionlike phenomena. It appears that the synchronization state may be used to characterize the depth of anesthesia.

Anesthesia↗

PubMed2000

Differential lusitropic responsiveness to beta-adrenergic stimulation in rat atrial and ventricular cardiac myocytes.

Cardiac myocyte relaxation is brought about mainly through Ca2+ uptake into the sarcoplasmic reticulum (SR) by a Ca2+-ATPase isoform, SERCA2a. Its activity is modulated by another protein, phospholamban (PLB). The levels of both proteins differ in some mammals between atrial and ventricular myocardium and this may lead to differences in relaxation, especially under stimulatory conditions. At a concentration of 100 nM, the beta-adrenergic agonist isoprenaline (ISO) accelerates the relaxation of rat papillary muscle more than that of the left atria (16.4 versus 4.0% hastening of time to 50% relaxation, respectively). Ventricular myocytes were 24.7% quicker in reaching 50% of their diastolic length after contraction when treated with ISO compared to atrial myocytes, which were only 3.6% faster. Ca2+ fluorescence transients were also abbreviated in ventricular compared to atrial myocytes exposed to ISO (41.9 versus 25.2% hastening of time to 50% peak Ca2+ respectively). Ca2+ uptake into ventricular SR vesicles was increased by 13% in the presence of protein kinase A while that into atrial SR vesicles remained unaffected. Western blotting analysis revealed 23% less SERCA2a protein, but 76% more PLB in ventricular compared to atrial tissue. We conclude that the distinct levels of SERCA2a and PLB in ventricular and atrial myocardium are responsible for the differential modulation of the relaxation process arising from beta-adrenergic stimulation in single rat atrial and ventricular myocytes.

Adrenergic beta-Agonists↗

PubMed2000

The contribution of lumbar sympathetic neurones activity to rat's skin blood flow oscillations.

Skin blood flow on the rat's paws using laser Doppler flowmeter, electrical activity of the heart (ECG) and respiration were measured simultaneously. The signals were recorded for 20 minutes, both before and after denervation, at core temperature 37 degrees C and 38.5 degrees C, that was maintained constant during the recordings. Spinal nerve fibres, at the level L3-L4, were transected. Experiments were performed on 15 adult Wistar rats under general anaesthesia. The oscillations in the measured signals were analysed in the time-frequency domain using wavelet transform. On the frequency region from 0.7 Hz to 5 Hz two characteristic peaks were observed in the skin blood flow spectrum. They correspond to the main peaks in the spectra of the ECG (around 3.3 Hz) and respiration (around 1.3 Hz). Several additional peaks were observed in the low frequency region, from 0.01 to 0.7 Hz, in all measured signals. In this frequency region the relative energy contribution of the blood flow oscillations decreased after denervation only in the denervated left hind paw. This difference was not statistically significant at 37 degrees C (p=0.098, Kruskal-Wallis test) but became statistically significant at 38.5 degrees C (p=0.017). Relative energy contribution of the low frequency region, from 0.01 to 0.7 Hz, decreased 2.5-fold in the blood flow of the denervated paw. Within this region the relative energy contribution decreased significantly in two intervals, from 0.01 to 0.08 Hz and from 0.08 to 0.2 Hz (p=0.023). In the higher frequency region, from 0.7 to 5 Hz, o statistically significant differences were obtained in any paws when compared before and after denervation at the same core temperature. We conclude that the activity of lumbar sympathetic neurones contributes to low frequency skin blood flow oscillations.

Animals↗

PubMed2000

Modification of skeletal muscle AChE expression by a novel method of stimulus application to the peripheral nerve.

We have developed a new method for chronic application of electrical stimuli to the rat peripheral nerve in vivo. This method has the following advantages: (1) the amplitude, duration and pattern of stimulation can be adjusted before and during the course of experiment, (2) the set-up allows the animal to move freely during the experiment, and (3) the set-up is constructed from inexpensive, of-the-shelf components that can be reused several times. The new method was used to study the influence of the pattern of muscle activation on acetylcholinesterase (AChE) regulation in extensor digitorum longus (EDL) and tibialis anterior (TA), fast skeletal muscles. Northern blot analysis of the chronically stimulated, fast EDL and TA revealed a rapid decrease of AChE mRNA level to a level typical for a slow, skeletal muscle.

Acetylcholinesterase↗

PubMed1999

Combined effects of glucocorticoids and electromechanical activity on the acetylcholinesterase expression in the fast rat muscle.

Protein synthesis is impaired in the glucocorticoid (GC)-treated fast mammalian muscle. Electromechanical activity was reported to alleviate this effect. Acetylcholinesterase (AChE; EC 3.1.1.7) synthesis in the skeletal muscle is regulated by both, GCs and electromechanical activity. In light of the above reports, one would expect that electrical stimulation will prevent GC-mediated fall of AChE synthesis in the muscle. On the other hand, a substantial body of evidence suggests that electromechanical activity exerts its effect at the AChE mRNA level, while GCs most probably act at the translational or early posttranslational level. Different levels of action would be more consistent with the independent and therefore additive influences of the two regulatory factors. In order to ascertain whether glucocorticoid and electromechanical effects interact in the control of AChE activity, we compared the effects of GCs on normal, nonstimulated fast rat skeletal muscle, with those of GC-treated and simultaneously electrically stimulated (tonic pattern, 10 Hz) muscle. Untreated and stimulated-only muscles were used as respective controls. The effects on the fast extensor digitorum longus muscle and slow soleus muscle, treated similarly were compared. As expected, chronic GC treatment and electrical stimulation of fast rat muscles with slow activity patterns both downregulated AChE activity. However, no additional decrease in AChE activity was observed, if stimulated fast muscle was simultaneously treated with GCs, suggesting that slow pattern of electromechanical activity prevents GC-mediated downregulation of AChE. The most plausible explanation of this observation is, that muscle activity blocks expression of some generally acting factors, which are induced by GCs and are responsible for the impaired synthesis of several proteins including AChE.

Acetylcholinesterase↗

PubMed1999

Organization and dissemination of multimedia medical databases on the WWW.

In the paper, we focus on the problem of building and disseminating multimedia medical databases on the World Wide Web (WWW). The current results of the ongoing project of building a prototype dermatology images database and its WWW presentation are presented. The dermatology database is part of an ambitious plan concerning an organization of a network of medical institutions building distributed and federated multimedia databases of a much wider scale.

Computer-Assisted Instruction↗

PubMed1996

Computer aided data acquisition and analysis of acetlycholinesterase velocity sedimentation profiles.

Acetylcholinesterase (AChE) is an enzyme that appears in several molecular forms. Individual AChE molecular forms can be isolated and identified on the basis of their velocity sedimentation profiles. We have improved an existing method for analyzing AChE sedimentation profiles with a computer aided data acquisition and analysis system. The software facilitates measurements of AChE activity of individual molecular forms and comparison among AChE velocity sedimentation profiles. In practice, our program increased precision and reduced the time of AChE velocity sedimentation profile analysis. The software can also be applied to velocity sedimentation analysis of other proteins. We plan to upgrade the program by making it compatible with Microsoft Windows.

Acetylcholinesterase↗

PubMed1991

Interactions between intrinsic regulation and neural modulation of acetylcholinesterase in fast and slow skeletal muscles.

1. Initiation of subsynaptic sarcolemmal specialization and expression of different molecular forms of AChE were studied in fast extensor digitorum longus (EDL) and slow soleus (SOL) muscle of the rat under different experimental conditions in order to understand better the interplay of neural influences with intrinsic regulatory mechanisms of muscle cells. 2. Former junctional sarcolemma still accumulated AChE and continued to differentiate morphologically for at least 3 weeks after early postnatal denervation of EDL and SOL muscles. In noninnervated regenerating muscles, postsynaptic-like sarcolemmal specializations with AChE appeared (a) in the former junctional region, possibly induced by a substance in the former junctional basal lamina, and (b) in circumscribed areas along the whole length of myotubes. Therefore, the muscle cells seem to be able to produce a postsynaptic organization guiding substance, located in the basal lamina. The nerve may enhance the production or accumulation of this substance at the site of the future motor end plate. 3. Significant differences in the patterns of AChE molecular forms in EDL and SOL muscles arise between day 4 and day 10 after birth. The developmental process of downregulation of the asymmetric AChE forms, eliminating them extrajunctionally in the EDL, is less efficient in the SOL. The presence of these AChE forms in the extrajunctional regions of the SOL correlates with the ability to accumulate AChE in myotendinous junctions. The typical distribution of the asymmetric AChE forms in the EDL and SOL is maintained for at least 3 weeks after muscle denervation. 4. Different patterns of AChE molecular forms were observed in noninnervated EDL and SOL muscles regenerating in situ. In innervated regenerates, patterns of AChE molecular forms typical for mature muscles were instituted during the first week after reinnervation. 5. These results are consistent with the hypothesis that intrinsic differences between slow and fast muscle fibers, concerning the response of their AChE regulating mechanism to neural influences, may contribute to different AChE expression in fast and slow muscles, in addition to the influence of different stimulation patterns.

Acetylcholinesterase↗

PubMed1991

Biochemical, morphological, and functional changes during peripheral nerve regeneration.

The success of axon regeneration after nerve injury should be judged by the extent to which the target organs regain their function. Recovery of muscle contraction involves axon regeneration, reestablishment of nerve-muscle connections, recovery of transmission, and muscle force. All these processes were investigated under the same experimental conditions and correlated in order to better understand their time-course and interdependence. The sciatic nerve of a rat was crushed in the thigh. The ingrowth of regenerating motor axons into the soleus (SOL) and extensor digitorum longus (EDL) muscles was monitored by measuring the activity of choline acetyltransferase (ChAT), a marker enzyme for cholinergic nerve terminals, in the muscles. The electron microscopic cytochemistry of acetylcholine esterase (AChE) was used to estimate the reestablishment of neuromuscular junctions in these two muscles. The recovery of muscle contraction was followed by measuring the force of isometric contraction in the triceps surae muscle in vivo. The pattern of ChAT recovery during reinnervation was similar in the EDL and SOL. The statistically significant increase of ChAT activity in these muscles, 14 d after the nerve crush, signified the entry of regenerating axons into the calf muscles. Electron microscopic cytochemistry revealed the first small nerve endings in contact with the denervated end plates 12 d after denervation. Subsequently, the number of reinnervated motor end plates and the surface area of the neuromusclar junctions steadily increased. The recovery of muscle force started between d 14 and 21 after the nerve crush. Thirty-five days after denervation, the difference between the muscle force of the reinnervated muscle and the control became statistically insignificant. Morphological normalization of the motor end plates was practically complete 33 d after denervation, concomitant with the normalization of the muscle force. At that time, however, ChAT activity in both muscles was still clearly subnormal (33.5% in EDL and 45% of the control in SOL) and therefore does not reflect the true extent of muscle force recovery. Yet, it seems that in spite of this, the regenerated nerve terminals contained sufficient amounts of acetylcholine (ACh) to trigger normal muscle contractions.

Animals↗

PubMedDate not supplied

The effect of insulin-like growth factor-1 on adult rat cardiac contractility.

There is increasing evidence that insulin-like growth factor-1 (IGF-1) may play a role in both physiological and pathophysiological events in the mammalian myocardium. The present study investigated the acute effects of IGF-1 on isometric force development in isolated rat cardiac muscle and on intracellular calcium (Ca2+) handling in isolated cardiac myocytes. IGF-1 had a positive inotropic effect on rat ventricular papillary muscles increasing force development by 17.8 +/- 4.6%, 18.5 +/- 5.8% and 11.9 +/- 4.9% (n = 12-20) at concentrations of 1, 10 and 100 ng/ml respectively. Isoprenaline increased tension in these papillary muscles by 56.7 +/- 7.7% at a concentration of 100 nM (n = 22). In comparison, insulin increased papillary muscle force development by 11.6 +/- 3.2%, 17.7 +/- 4.1% and 19.7 +/- 5.6% at concentrations of 1, 10 and 100 nM respectively (n = 16-20). In the single cardiac myocyte IGF-1 increased, the peak cytosolic free Ca2+ concentration, the amplitude of the Ca2+ transient and the time to peak Ca2+ as measured with the fluorescent bioprobe Indo-1 AM. The positive inotropic response to IGF-1 by rat ventricular muscle is therefore associated with a rise in free, peak cytosolic Ca2+ in isolated cardiac myocytes. Increasing insulin concentrations (1-1000 nM) elicited a progressive elevation in isometric force and free, cytosolic Ca2+. In contrast, in the presence of IGF-1, the maximal rise in isometric force and free cytosolic Ca2+ were both observed at 10 ng/ml. Recent reports have suggested that IGF-1 may act on the mammalian myocardium when administered chronically, but this study is amongst the first to demonstrate an acute effect of IGF-I on the mammalian heart. IGF-1 may prove then to be a novel cardioactive agent in both normal and pathophysiological states.

Animals↗

PubMedDate not supplied

A novel staining method for quantification and 3D visualisation of capillaries and muscle fibres.

The aim of this study was to introduce a combined fluorescent staining that clearly demonstrates capillaries and distinguishes them from the basal lamina of muscle fibres in skeletal muscle tissue. The triple staining with CD31, Griffonia (Bandeira) simplicifolia lectin (GSL I) and laminin efficiently distinguishes vascular endothelium from the basal lamina of skeletal muscle fibres in physiological and pathological conditions. The presented triple staining method has several advantages, which facilitate quantitative analysis of the capillary network, and its relation to individual muscle fibres.

Animals↗