Angiotensin II (ANG II) significantly increased noradrenaline (NA) uptake by cortical, hypothalamic and hippocampal synaptosomes thus activating noradrenergic neurotransmission. ANG II did not affect NA uptake by striatal synaptosomes. The interaction between AT1 receptors and noradrenergic neurons and the involvement of brain noradrenergic neurotransmitter system in ANG II-induced drinking in rats is suggested by the increase of NA uptake in hypothalamus and frontal cortex which are rich in AT1 receptors and are of importance for drinking behavior. The ANG II-receptor antagonists losartan, EXP 3174, sarmesin and saralasin decreased NA uptake in all brain regions studied as compared to the uptake in the same brain regions of ANG II-injected animals thus antagonising the effect of ANG II. There is no relationship between the inhibition of ANG II-induced water intake and the changes of NA uptake under the effect of the ANG II-receptor antagonists.
The aim of this study was to compare classical Balke and Bruce protocols with our modification of Balke protocol in pediatric cardiorespiratory diagnostics. The modification of Balke consists of nine stages per 1 min at a constant velocity of 5.6 km x h(-1) and increasing elevation from 6% to 22% in 2% increments. Sixty healthy children (mean age = 13.3+/-0.2 years; BMI = 18.8+/-0.6 kg x m(-2); mean +/- 95% CI), divided into three groups of 20 children each, matched by age, height and BMI performed integrative cardiopulmonary exercise testing using one of the treadmill protocols mentioned. At the end of each exercise increment and throughout the recovery period the children were asked to rate the perceived exertion (RPE) using the Borg Category Ratio scale--CR-10. Exercise results showed that Balke protocol had the longest duration (21.7+/-0.6 min.) and the lowest values for VO2/kg (34.2+/-1.8 ml x min(-1) x kg(-1)) due to the minimal workload increments. Bruce protocol had intermediate duration (14.9+/-1.1 min.) and children achieved the highest VO2/kg (48.6+/-2.7 ml x min(-1) x kg(-1)) but the test is symptom-limited which is ethically unacceptable in childhood. Exercise data revealed that our modification of the classical Balke protocol had an optimal duration (11 min.) and yielded peak VO2/kg values (39.4+/-2.3 ml x min(-1) x kg(-1)) adequate for evaluation of children's exercise capacity. Children's ratings of perceived exertion were highest in Bruce protocol (6.5+/-0.4) and lowest in the original Balke protocol (4.5+/-0.8). In conclusion, the modification of Balke protocol is suitable and reliable for screening and clinical testing in pediatric age group.
Cholecystokinin (CCK) is a classical brain-gut peptide that exerts a variety of physiological actions in the gastrointestinal tract and central nervous system. CCK occurs in several molecular forms of varying aminoacid length, the sulphated octapeptide (CCK-8) being the predominant form in the brain. CCK mediates its effects through interaction with specific receptors subdivided in two subtypes--CCK-A (present in the periphery and in few selected brain nuclei) and CCK-B (the predominant receptor subtype in the brain). CCK is implicated in variety of behavioral functions as satiety, anxiety, exploratory and locomotor activity and learning and memory. After a brief description of the distribution, molecular forms, release, inactivation, etc. of CCK in the brain, the present review summarizes the recent data on the role of CCK in learning and memory. The memory-enhancing effects of CCK have been demonstrated in various types of memory. Data showing that CCK-A receptors mediate mnemonic while CCK-B receptors mediate amnestic effects are also presented.
The effects of peptide and nonpeptide angiotensin II (Ang II)-receptor antagonists (losartan, EXP-3174, saralasin and sarmesin) on the levels of the biogenic monoamines dopamine, noradrenaline and serotonin in the frontal cortex, striatum, hypothalamus and hippocampus of rats with Ang II-induced water intake were investigated. Ang II administered i.c.v. at a dose inducing drinking behavior in rats significantly changed the levels of biogenic monoamines. The latter were also significantly affected by the Ang II-receptor antagonists, as in most cases the drugs antagonized the effect of Ang II. Most pronounced were the effects of Ang II and Ang II-receptor antagonists on the dopamine levels. These levels were reduced to zero after Ang II in all brain structures studied. The drugs tested increased the dopamine levels, restoring their values to the values in vehicle-injected rats. Ang II-receptor antagonists exerted mosaic effects on noradrenaline and 5-HT (serotonin) levels depending on both--the type of biogenic monoamine and the brain structure. There was no relationship between the inhibition of Ang II-induced water intake and the changes in the levels of brain biogenic monoamines under the effect of the Ang II-receptor antagonists. These antagonists may play a role in the modulation of brain monoaminergic neurotransmitter systems.
Oxygen uptake efficiency slope (OUES) is an index meant to provide an objective measure of cardiopulmonary function at submaximal exercise. The aim was to study the exercise performance and OUES in obese children performing standardized exercise. Sixty children aged 6-17 years performed incremental treadmill exercise test. They were divided into two groups matched by age, sex and height: thirty obese subjects (15 girls/15 boys; BMI = 27.4+/-1.7 m x kg(-2)) and 30 controls (BMI = 18.8+/-1.0 m x kg(-2)). Perceived exertion was assessed by means of CR-10 Borg scale. The duration of the exercise for the obese children was significantly shorter than for controls (p = 0.010) but obese children had greater absolute values for oxygen uptake (VO2 peak mL x min(-1) = 1907+/-249 vs. 1495+/-208; p = 0.013) which, adjusted for body mass, decreased significantly (VO2/kg mL x min(-1) x kg(-1) = 29.2+/-1.4 vs. 33.6+/-1.3; p < 0.001). OUES correlated strongly with VO2 peak (r = 0.91) and oxygen pulse (r = 0.80), as well as with anthropometric variables height (r = 0.88) and age (r = 0.83). Extremely high correlation was found between OUES calculated for 100% of exercise duration and OUES at the anaerobic threshold (r = 0.979; p < 0.001). No significant differences were found between the studied groups concerning the absolute values of OUES. Obese children rated perceived exertion significantly higher than controls (Borg score 6.2+/-0.4 vs. 5.2+/-0.4; p = 0.001). In conclusion, the absolute metabolic cost of exercise and perceived exertion were higher in the obesity group. OUES is an objective measure of cardiopulmonary reserve that doesn't require a maximal effort but it is considerably dependent on anthropometric variables which impedes its interpretation as exercise index in childhood.
The age-related differences in the synapses of the paraventricular hypothalamic nucleus (PVN) were studied with transmission electron microscopy in young (3-month-old) and senescent (25-month-old) Wistar rats. The changes in the axodendritic (ADS) and axospinous (ASS) synapses in the PVN neuropil were determined by morphometry. The majority of synapses were of the ADS type. In senescent rats the density of both ADS and ASS was diminished. The mean area of the ASS presynaptic boutons in aged rats was more enlarged than of the boutons in the ADS. The parameters characterising synaptic vesicles (SV) were diminished in aging rats. The number of SV per synaptic bouton decline was not significantly different. The changes in the length of synaptic contact zone (SCZ) were not significant with the exception of the total SCZ length per 1000 microm2 and the total area of the SCZ per 1000 microm3 in the ADS. The decrease of the number of dendritic spines (DS) per 1000 microm2 in the neuropil was significantly age-related diminished. Moreover, the mean area of the DS was significantly enlarged.
The OLETF rat develops microangiopathic complications similar to human diabetes and is considered a useful model of Type 2 DM. Erythrocyte, platelet and leucocyte abnormalities described in diabetic patients are thought to play a role in the development of diabetic microangiopathy. This study was designed to investigate whether OLETF rats show hematological alterations and the effect of sucrose treatment on metabolic and blood parameters. Hematological parameters, body weight, food and water intake, fasting and non-fasting blood glucose (BG) and HbA1c were measured in OLETF rats treated for two months with 30% sucrose added to drinking water. Non-treated OLETF rats and non-diabetic Long-Evans Tokushima Otsuka (LETO) rats were used as controls. In the control OLETF rats the number of platelets (Plt) and red blood cells (RBC) was higher, while the mean cell volume (MCV) and the mean cell hemoglobin content (MCH) were lower compared with LETO. Mean cell hemoglobin concentration (MCHC) was significantly higher in the diabetic rats. Sucrose administration decreased food intake and body weight and increased fasting blood glucose and HbA1c. It resulted in a decrease of RBC, Hb, Hct, MCV and MCH compared with control OLETF, while Plt count increased significantly. Our results point to significant alterations in erythrocyte count and morphology and Plt count in diabetic OLETF rats compared with non-diabetic LETO. Sucrose administration accelerated the development of diabetes, affected blood cells inducing the suppression of RBC and an increase in Plt count and some of its effects persisted after sucrose withdrawal.
We intended to study the effect of swimming exercise on the brain, liver and heart malondialdehyde (MDA) levels which are the last product of oxidation, and to compare them with the brain, liver and heart MDA levels of controls. The experiments were carried out on 20 Wistar rats which were fed with a standard laboratory chow diet ad libitum. Rats were distributed in two groups, control group (n = 10) and exercise group (n = 10). The exercise group rats were exposed to swimming exercise for 30 minutes. After this animals in each group were sacrificed by decapitation, their brain, liver and heart tissues were quickly removed. MDA levels of the brain, liver and heart were determined according to the method in which MDA reacts with thiobarbituric acid. Results were evaluated by the Mann-Whitney U test. The liver and heart MDA levels in the exercise group were (29.59+/-6.73 and 10.49+/-1.90 nmol/g tissue, respectively) significantly higher than in the control group (21.78+/-3.46 and 8.86+/-1.25 nmol/g tissue, p<0.01 and p<0.05, respectively). However, the brain MDA levels were similar in both groups (exercise group 19.37+/-5.50 nmol/g tissue and control group 16.58+/-2.44 nmol/g tissue; p=0.325). It is concluded that swimming exercise might cause oxidative stress.
This paper deals with the effects of high (microwave) and extremely high (millimetre waves, MMW) frequency electromagnetic fields on the membrane processes and ion channels, molecular complexes, excitable and other structures. Microwaves as well as millimetre waves are widely used in medical practice and in everyday life. The existence of interaction between the exogenous and endogenous electromagnetic fields with biological systems is now a subject of intense discussion. The most contentious question is the existence of a possible specific (non-thermal) effect of microwaves, unrelated to that caused by increased temperature. Although numerous data have been published on the possible non-thermal effects of the studied electromagnetic fields on different kinds of living systems, only little understanding is gained about the modes of microwave action. Here we review data, which provide evidence that non-thermal microwave effects do exist and may play a significant role. This evidence is based on research at all biological levels, from cell-free systems through cells, tissues and organs, to animal and human organisms.
Natural sulfated polysaccharides (SPs) derived from brown seaweed comprise a complex group of macromolecules with a wide range of important physiological properties. SPs have been shown to bind and directly regulate the bioactivity of growth factors and cytokines such as basic fibroblast growth factor, interferon, various enzymes and transforming growth factor. Myostatin is a member of the transforming growth factor-beta (TGF-beta) family that acts as a negative regulator of skeletal muscle mass. In this work we demonstrated that SPs isolated from the brown seaweed Cystoseira canariensis bind to the myostatin protein in serum.
The aim of the present work was to study the antioxidant activity of the new derivative of succinic acid-succinate mono[(2-dimethyl-amino) ethyl ether] of succinic acid (yackton) under conditions of hypoxic and hemic hypoxia as well as to examine in vitro the antiradical activity of this preparation. Hypoxia in the rats was modelled by: (i) allowing the rats to breath a gas mixture with 7% O2 and 93% N2 for 30 minutes (hypoxic hypoxia), and (ii) injecting the rats sodium nitrite subcutaneously in a dose of 60 mg/kg body weight (hemic hypoxia). Yackton was injected intraperitoneally to both groups 30 minutes before the extreme influence in a dose of 140 mg/kg body weight. Then in homogenates and in post-mitochondrial fractions of liver, heart, lungs, brain we studied the content of secondary products of lipid peroxidation (LPO), activity of antioxidant enzymes superoxide dismutase (SOD) and catalase, and the activity of enzymes responsible for the maintenance of reduced glutathione (GSH) glutathione reductase (GR-ase) and glutathione peroxidase (GP-ase). In vitro studies were made on the antiradical activity of yackton in reaction with the stable radical diphenylpicrylhydrazine (DPPH) as well as on the reaction velocity of the preparation with DPPH, and its period of semi-transformation in a non-radical form. It was shown that yackton treatment before hypoxic and hemic hypoxia decreased lipid peroxidation (LPO) level and increased SOD activity. After the yackton injection the state of glutathione system was normalized in comparison with its state at hypoxic and hemic hypoxia. Yackton had no antiradical properties in vitro. We concluded that yackton promotes optimization of prooxidant-antioxidant homeostasis of the organism under the hemic and hypoxic hypoxia acting as antioxidant of a non-direct action.
An inverse relationship between HDL-c plasmatic levels and Li+ flux (Na+-Li+ exchange mediated) has been reported in normotensive individuals with hypertensive ancestors as well as in essential hypertensive subjects. This lipoprotein reaction with plasmatic membrane components induces modifications in membrane transport mechanisms as well as in cellular enzymes. In this paper we present data on Li+ flux (Na+-Li+ exchange mediated) in red blood cells from normotensive individuals without hypertensive ancestors. Kinetic analysis of Li+ efflux as a function of Na+(extracell) concentration was carried out. Vmax and Km values were determined. HDL-c plasmatic levels were also determined. Vmax showed a significant inverse correlation with HDL-c levels. No significant correlation of Km values with HDL-c levels was observed. The data presented support previous data showing that variable Vmax is sensitive to cellular environmental factors. Otherwise the Km variable not influenced by these factors is sensitive to hereditary influences.
OBJECTIVES:To determine A-waves of a family with autosomal recessive form of demyelinatig hereditary motor and sensory neuropathy Lom (HMSNL).METHODS:A-waves were investigated during conventional F-wave study of family members with HMSNL which had genetic testing.RESULTS:During routine F-wave studies A-waves were observed in all tested nerves. They appeared between M-responses and F-wave. The A-waves were with low amplitude, shorter duration and constant shape and latency than F-waves. They appeared independently of F-waves. A-waves were more often recorded as multiple waves in lower and upper extremities. More than three A-waves per nerve were found mostly in ulnar and facial nerves. In 16 cases A-waves were found in the absence of F-waves.CONCLUSION:It is assumed that the A-waves could be seen as additional signs of pathology because they were not observed in unaffected members of the family and in healthy subjects.
We studied the influence of stance width and vision on the plantar pressures for the left and right foot during bipedal quiet standing on the pressure-sensitive insoles. The support widening shifted the left and right centers-of-foot-pressure (CFPs) laterally and forward (right foot), diminished SDs of: the left and right mean plantar pressures (MPPs), the anteroposterior and mediolateral displacements of left and right CFPs. It also decreased negative correlations between left and right MPPs and between mediolateral displacements of left and right CFP and increased positive correlation between anteroposterior displacements of left and right CFPs, more expressive with eyes-open. The later results suggested that support widening increased the weight of exploratory behaviour regarding anteroposterior equilibrium and decreased exploratory sway serving mediolateral equilibrium. Eyes' closure lead to a small left bias of the body-weight-bearing and forward shift of the left versus right CFP, thus suggesting that vision increased bilateral symmetry of stance.
Several mechanisms were investigated by which the Jendrassik manoeuvre might potentiate tendon jerk and H-reflexes, recorded here as surface EMG from the triceps surae muscle group. If fusimotor activation is involved, then, after muscle conditioning designed to leave spindles in a slack state, interposing a Jendrassik manoeuvre before reflex testing should have increased reflex amplitude by restoring spindle sensitivity; but this was not the case. The Jendrassik manoeuvre failed to increase facilitation of the soleus H-reflex by a quadriceps volley, contrary to expectations if it operates by presynaptic disinhibition. There was no increase in the level of ongoing EMG during a Jendrassik manoeuvre, indicating that it does not operate by direct facilitation of motoneurones. The Jendrassik manoeuvre produced less reflex potentiation when spindles had a high rate of resting discharge. A remaining, untested mechanism is the modulation of oligosynaptic pathways that may contribute to the largely monosynaptic reflex response.
Two experiments addressed the issue of the role of (learned) action effects in response planning. In an initial acquisition phase participants perveived that each of their responses to visual stimuli would produce a particular stimulus contingent to the given action-demanding stimulus. In a succeeding test phase targets were presented together with noise elements which (among others) would or would not represent (learned) effects of the response to the target stimulus. We obtained an effect of the effect-compatibility indicating that noise elements representing the effect of the to-be-executed response allowed for faster responding. These findings suggest that anticipations of action effects play a functional role in response planning.
Surface EMG signals were detected from the biceps brachii muscle of five subjects using linear electrode arrays during isometric voluntary contractions at low force levels. A classification method based on neural networks has been used to identify the active motor units during the contraction. In addition, surface EMG global variables have been computed. It was found that at low contraction levels it is possible to reliably identify motor unit action potentials from the interference surface EMG signal and to classify them as belonging to different motor units. Progressive recruitment of new motor units during long duration contractions was observed in all the investigated cases from the first few minutes of contraction (3-4 minutes), indicating a change in the recruitment threshold of non-active motor units as a consequence of muscle fatigue. The recruitment of new motor units was more pronounced for higher force contraction levels than for the lower ones. This behaviour was confirmed in two out of five cases by changes of the global EMG variables.
For rehabilitation of cerebral paresis, e.g. following stroke, we developed a Method that helps to relearn lost movements of paretic arms, hands and fingers. The concept is to restore the lost proprioceptive afferent inflow to the CNS to facilitate reorganization by neuromodulation. Continuous movements are induced using closed-loop position controlled functional magnetic stimulation (FMS). In order to induce a equivalent proprioceptive afferent pattern to the lost pattern, the controller has to elicit movements of single fingers using a physiological stimulation frequencies in the range of 15 to 40 Hz. It has to integrate the remaining voluntary motor performance of the paretic extremity while stimulating. The presented controller is able to induce smooth movements and lifts the finger into the target position within two seconds. Following the stimulation of the plegic finger extensors the patients could perform rapid finger extension movements with larger displacement amplitude and velocity at rather diminished amounts of activity (EMG).
In the present study motor unit (MU) firing pattern was analysed during long-term static contraction in order to see if fatigue would induce rotation of activity between different MU. Surface as well as intramuscular EMG were obtained from ten subjects during a sustained hand lift for 5 minutes after performance of a 30% MVC fatiguing contraction of the extensor carpi radialis muscle. A newly developed decomposition program constituted a powerful tool to obtain detailed knowledge of long term activity pattern of MU during low force contractions. Although the muscle was highly fatigued the majority of MU showed a continuous firing pattern after recruitment and no clear incidences of rotation were found for any of the subjects. Therefore, long term, low force contractions, as performed during many occupational work tasks, may involve continuous activation of the low threshold MU and this could have mechanical as well as metabolic implications for these muscle fibers.
The information transmission properties of single, deefferented, primary muscle spindle afferents (MSAs) from the hind limb of the cat were investigated. Random stretches were delivered to the gastrocnemius medialis muscle, while recording spike trains from several MSAs near the dorsal root. Two classes of input stimuli were used: Gaussian noise with band-limited flat spectrum, and Gaussian noise with a more "naturalistic" 1/fn spectrum. The "reconstruction" method was used to calculate a lower bound to the information rate (in bit/ sec) delivered from MSAs to the spinal cord. Results show that in response to flat spectrum primary MSAs transfer information mainly about high frequencies, carrying 1.97 bits per spike. In response to naturalistic spectrum MSAs transfer information about both low and high frequencies, with "spiking efficiency" increasing to 2.99 bits per spike. A simple muscle spindle model was simulated, exemplifying the part of the intrafusal fiber mechanical properties in information transmission.
