Cellular brain edema induced by water intoxication in rat experimental model.

OBJECTIVES: This paper presents our own rat model of the cellular brain edema, induced by water intoxication (WI). The basic principle of the model is an osmotic imbalance in the cell membrane followed by an intracellular flow of sodium and simultaneous accumulation of water leading to the subsequent increase of BBB permeability. METHODS: The usefulness of the model was tested in precisely specified conditions whose results were clearly expressed. The procedure determined both how WI induces cellular edema as well as the disturbances caused by cellular edema. RESULTS: The evidence of existing cellular edema with increased BBB permeability was proved by intracellular accumulation of intravital dye with a large molecular size; increased brain-water content was confirmed by using the dry/wet weight method and by the decrease in CT density; the elevated intracranial pressure (ICP) due to the expanding volume was determined by continuous monitoring the ICP; the structural lesions were proved by identification of the myelin disintegration; and the impaired nervous functions was demonstrated by the of open field test method. CONCLUSION: Our experimental model can help the future studies of pathophysiology of cellular brain edema and is suitable for testing neuroprotective agents.

Locomotion in young rats with induced brain cellular edema - effects of recombinant human erythropoietin.

OBJECTIVES: Effect of recombinant human erythropoietin (rhEPO) on spontaneous motor activity was tested in young rats after intraperitoneal (i.p.) administration of rhEPO, followed by induction of cellular brain edema (CE). Induced changes in the spontaneous horizontal locomotor activity was studied by open field test (OFT). METHODS: CE was induced by water intoxication (WI) using standard method of fractional hyperhydration accompanied with desmopressin administration. Using the accepted method of OFT average time spent in locomotion (s) was determined. 48 young rats at the age of 25, and 35 days were divided into three groups - controls, rats after WI (OFT followed after 44 hours), and rats administered with rhEPO prior to application WI (OFT after 48 hours). RESULTS: In 35-day-old rats rhEPO administration increased the spontaneous locomotor activity, previously decreased by cellular edema. In 25-day-old rats, rhEPO administration prior to the induced CE, decreased spontaneous locomotor activity. CONCLUSION: Presented results demonstrate the neuroprotective capacity of rhEPO, manifested by elimination of the suppressive influence of CE on the locomotion in 35-day-old rats. In 25-day-old rats the neuroprotective effect was not present. These results confirmed that the 10 day interval in the development may represent a different stage of brain maturation in the relation to the neuroprotective effect of rhEPO.

An experimental model of the "dual diagnosis": Effect of cytotoxic brain edema plus peripheral neuropathy on the spontaneous locomotor activity of rats.

OBJECTIVE: The aim of the study was to find how a simultaneous impairment of the CNS (cellular brain edema induced by water intoxication) and PNS (blockade of the right forelimb brachial plexus by local anesthewtic - Marcaine) affects spontaneous locomotor activity of adult rats. METHODS: Rats were divided into groups of animals without water intoxication (without WI) - A,B,C, and those that were water intoxicated (induction of brain edema - after WI) - D,E,F. Both groups were further divided into intact ones (A,D), animals with PNS lesion (Marcaine) (B,E) and sham-operated animals (C,F). Locomotor activity (LA) of the rats was tested by the open field test. RESULTS: LA of rats with both CNS and PNS impairment (WI + Marcaine) was significantly suppressed compared to the activity of control rats. Comparison of LA of rats with a single lesion - PNS impairment only (Marcaine only), CNS lesion only (WI) to those animals with both lesions (WI + Marcaine) revealed even larger decrease of LA of rats with combined lesions, which represents a model of the dual diagnosis. Also the pattern of behaviour of rats in both sham operated groups was different, which apparently depended on water intoxication. CONCLUSION: The presented results show that the LA of rats with combined lesions is significantly lower compared to the activity of rats with a single lesion in the CNS or PNS. Results also indicate that the already induced endoneurial edema prevents subsequent accumulation of water applied to the intimate vicinity of the peripheral nervous structures.

Study of locomotion, rearing and grooming activity after single and/or concomitant lesions of central and peripheral nervous system in rats.

OBJECTIVE: Locomotion, rearing and grooming represent different forms of behaviour and motor activity in rats. In this study, changes in these activities were analysed in relation to impaired function of the nervous system by single and/or concomitant lesions representing an experimental model of the dual diagnosis. METHODS: 32 rats were divided into 4 groups of 8 rats: intact rats, rats with single lesion of peripheral nervous system (PNS) - Marcaine neuropathy, rats with single CNS lesion - cellular brain edema induced by water intoxication, and the concomitant lesions (combination of CNS and PNS lesion in one rat). Water intoxication was performed in a standard way by fractionated hyperhydration. The average time spent by locomotion, rearing and grooming was registered and analyzed using an open field test. RESULTS: All activities of the rats after water intoxication became inhibited due to the generally suppressive effect of brain edema. Lesion of PNS reduced activity in locomotion only, because for rearing and grooming activities, the function of the forelimb is not dominant. Combination of lesions (dual diagnosis) reduced locomotion and rearing activity more than single lesions, and enhances the stressogenic effect, which was manifested by a long periods of grooming. CONCLUSION: Results of our study confirmed the physiological and pathophysiological differences in the movement stereotype between locomotion, rearing and grooming caused by the characteristics and algorithms of the movements, which are inborn to rats - the dominant role of the forelimbs in locomotion, the dominant exploratory activity in rearing, and the precise syntactic movement pattern in grooming.

Neuronal excitability changes depend on the time course of cellular edema induced by water intoxication in young rats.

OBJECTIVES: The aim of the study was to determine whether the functional state of neurons is affected by the duration of the induced cellular edema and by the age of animals tested. The cellular edema was induced by water intoxication and neuronal functions were tested by the standard method of electrical stimulation of neurons of the cerebral cortex. METHODS: water intoxication was induced by standard method of fractionated hyperhydration. Excitability of cortical neurons was tested by cortical stimulation with the intensity required to induce cortical afterdischarge (AD). Animals were divided into three experimental groups (B, C, D) and three control groups (AB, AC, AD). Experimental groups differed in age of water intoxication (12 or 25 days) and age of excitability testing (25 or 35 days). Changes in the duration of AD (seconds) were statistically evaluated. RESULTS: Duration of cortical afterdischarges (AD) in the control groups was at the level literature data. In all experimental groups (B, C, D), excitability of cortical neurons was markedly inhibited. AD was possible to induce only in some of the animals and its average duration was significantly shorter than in control groups. CONCLUSION: This inhibitory effect can be explained by persistent impairment of astrocyte-to-neuron communication, which plays a key role in the process of formation of structural and functional changes during cellular edema. Some of the functional manifestations of the developing edema are influenced by the age of experimental animals. At least some events of this process are not influenced by the age of experimental animals.

Adipose Tissue as an Endocrine Organ: An Update on Pro-inflammatory and Anti-inflammatory Microenvironment.

Adipose tissue is recognized as an active endocrine organ that produces a number of endocrine substances referred to as "adipokines" including leptin, adiponectin, adipolin, visfatin, omentin, tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), resistin, pigment epithelium-derived factor (PEDF), and progranulin (PGRN) which play an important role in the food intake regulation and significantly influence insulin sensitivity and in some cases directly affect insulin resistance in skeletal muscle, liver, and adipose tissue. The review summarizes current knowledge about adipose tissue-derived hormones and their influence on energy homeostasis regulation. The possible therapeutic potential of these adipokines in the treatment of insulin resistance, endothelial dysfunction, a pro-inflammatory response, obesity, eating disorders, progression of atherosclerosis, type 1 diabetes, and type 2 diabetes is discussed.

Neuronal excitability after water intoxication in young rats.

OBJECTIVES: Our previous experiments with animal models revealed that water intoxication induces brain oedema and opens plasma membranes. Present study is aimed to determine whether the standard method of hyperhydration can influence cerebral microenvironment also in young rats. Neuronal functions were tested by standard electrical cortical stimulation. METHODS: Hyperhydration was induced by administration of distilled water (DW) intraperitoneally. Three groups of young rats were used: 12, 25, and 35-day-old. Cortical excitability was tested 19 to 20 hours after DW administration by electrical stimulation of the sensorimotor cortex with intensity necessary to elicit cortical afterdischarges (AD). Water content in the brain was estimated by dry/wet ratio and value of natremia by standard biochemical examination. Control animals of the same age groups were tested in the same way, only they did not receive DW. RESULTS: Brain water content in hyperhydrated animals was smaller than in controls in all studied age groups. Natremia was the same (normal) in both the hyperhydrated and control animals aged 25 days. Excitability of cortical neurons in young hyperhydrated animals was significantly inhibited in comparison to the same age groups of controls. CONCLUSION: Hyperhydration induced in young rats (12, 25, 35-day-old) had different effects than in adults. Absence of hyponatremia, lower water content in the brain and significant inhibition of cortical excitability can be explained on the basis of ontogenetically dependent aquaporine expression (AQP 4) and different activity of ionic membrane transporters.

Effects of a single dose of erythropoietin on motor function and cognition after focal brain ischemia in adult rats.

We tested the influence of erythropoietin (EPO), a basic cytokine in erythropoiesis regulation, on the process of motor function and cognition after focal brain ischemia induced by a local application of endothelin. Endothelin-1 (ET-1) induced short lasting strong vasoconstriction, with described impact on the structure and on the function of neuronal cells. Neurological description of motor function and Morris water maze test (the swimming test is one of most widely used methods for studying cognitive functions in rodents) were used to study the process of learning and memory in three-month-old male albino Wistar rats (n=52). Both tests were performed one week before, and three weeks after ischemia induction (endothelin application on the cortex in the area of a. cerebri media dx.). Experimental group received i.p. injection of EPO (5,000 IU/kg body weight, 10 min before endothelin application). Control group of animals received one i.p. injection of saline at the dose of 1 ml/kg body weight at the same time. Only sham surgery was performed in the third group of animals. Rats with EPO pretreatment before the experimental lesion exhibited significantly better motor and cognitive function then those with saline injection. No significant changes in the motor and cognitive function were found in the third group of rats (sham operated controls).

Ascorbic acid and alpha-tocopherol protect age-dependently from hypoxia-induced changes of cortical excitability in developing rats.

OBJECTIVES: The effects of ascorbic acid and α-tocopherol pre-treatment on hypoxia induced changes in brain cortex excitability were tested in immature rats exposed chronically to simulated altitude of 7 000 m. METHODS: Rat pups were kept together with their mothers for 8 hours a day in hypobaric chamber since the day of the birth till the postnatal day 11 or 17. Each day immediately before placing to hypobaric chamber pups were pretreated intraperitoneally either with ascorbic acid (100 mg/kg) or α-tocopherol (1 500 mg/kg). Cortical afterdischarges were elicited by repeated stimulation of the right sensorimotor cortex. The duration of evoked cortical afterdischarges was analyzed. RESULTS: Duration of cortical afterdischarges progressively declines with age. Hypoxia prolonged the duration of afterdischarges in 12-, 18- and 25-day-old animals. Pretratment with ascorbic acid or α-tocopherol shorted afterdischarges duration in youngest experimental group when compared with animals exposed to hypoxia only. CONCLUSION: Hypoxia significantly affects the brain cortex excitability by prolonging afterdischarges duration. This effect differs with age. Antioxidant pre-treatment brought about shorter duration of cortical afterdischarges only in the youngest experimental group. The antioxidant effect is therefore age dependent.

Impact of chronic ethanol intake of rat mothers on the seizure susceptibility of their immature male offspring.

The aim of present study was to examine the impact of prenatal ethanol exposure on seizure susceptibility of the offspring. Pregnant Wistar rats were compelled to drink either 10% or 20% ethanol solution, as the only drinking fluid since conception up to the weaning of their offspring at the age of 28 days. Pregnant and nursing rats of the control group drank water. Electrophysiological experiments (repeated electrical stimulation and analysis of cortical afterdischarges duration) were than performed on their immature offspring. Rat pups were tested on postnatal day 18, 25, and 35. Shortening of afterdischarges duration was observed in 18-day-old animals (mothers drank 20% ethanol) when compared with age matched controls and failure of post-ictal depression phenomenon was found in 25- and 35-day-old animals. Our findings signalize that ethanol exposure during pregnancy influences seizure susceptibility by acting on excitatory/inhibitory brain systems and this effect is dose- and age-dependent.

Nicotine reduces mortality of developing rats exposed to high-altitude hypoxia and partially suppresses the duration of cortical epileptic afterdischarges.

Nicotine has been repeatedly reported as substance possessing neuroprotective properties. This study focused on the possible beneficial effects of nicotine against the high-altitude hypoxia (9000 m for one hour). 15 min prior to hypoxia exposition rats (12- and 35-day-old) were treated with nicotine. Next day electrodes have been implanted and the effects of nicotine and hypoxia (or both factors) on duration of afterdischarges (ADs) were tested. Administration of nicotine declined the hypoxia-induced mortality in 35-day-old animals. Nicotine pretreatment had no effect on ADs duration in 12-day-old pups, therefore brought about suppression of ADs in 35-day-old animals. Taken together, our data show that nicotine exhibits an anticonvulsant effect that is age-dependent. The mechanisms of nicotine neuroprotective properties include probably the influence of calcium homeostasis, increase synthesis of variety of growth factors, inhibition of the caspase cascades and antioxidant capability of nicotine.

Effect of methylprednisolone on experimental brain edema in rats - own experience reviewed.

Brain edema - a frequently fatal pathological state in which brain volume increases resulting in intracranial pressure elevation - can result from almost any insult to the brain, including traumatic brain injury. For many years, the objective of experimental studies was to find a method to prevent the development of brain edema at the onset. From this perspective, the use of methylprednisolone (MP) appears promising. High molecular MP (MW>50 kDa) can be incorporated into the brain - in the conditions of the experimental model - either by osmotic blood-brain barrier disruption (BBBd) or during the induction of cellular edema by water intoxication (WI) - a condition that increases the BBB permeability. The time window for administration of the MP should be at the earliest stages of edema. The neuroprotective effect of MP on the permeability of cytoplasmatic membranes of neuronal populations was proved. MP was administrated in three alternative ways: intraperitoneally during the induction of cytotoxic edema or immediately after finishing cytotoxic edema induction in a dose of 100 mg/kg b.w.; into the internal carotid artery within 2 h after finishing cytotoxic edema induction in a dose of 50 mg/kg b.w.; into internal carotid artery 10 min after edema induction by BBBd in a dose of 50 mg/kg b.w.

Nicotine effects on rat seizures susceptibility and hippocampal neuronal degeneration.

OBJECTIVES: Nicotine is a widely used drug of abuse exerting number of effects on the central nervous system. The study was aimed at the effects of nicotine in various doses on the excitability of cerebral cortex and - by using the methods of histochemistry - to identify possible signs of neuronal degeneration after nicotine administration. METHODS: Cortical afterdischarges were elicited by repeated stimulation of the right sensorimotor cortex. The duration of evoked ADs was monitored in animals treated with nicotine (0.75 or 1.0mg/kg) and in animals treated with saline. Methods of histochemistry (Fluoro-Jade B and bis-benzimide) were used to detect possible neuronal degeneration in hippocampus or in cerebral cortex. RESULTS: No Fluoro-Jade B positive cells were found in hippocampi of control animals, or animals treated with nicotine. ADs length was significantly influenced by administration of nicotine. CONCLUSION: Nicotine in 0.75 or 1.0 mg/kg dose leads to the decrease in ADs duration, influences the seizure susceptibility, and doesn't cause any detectable neuronal damage.

Melatonin modulates hypoxia-induced changes of rat brain excitability.

The aim of our study was to test the hypothesis, if melatonin pre-treatment (in dose of 100 mg/kg) can influence the changes of brain function after short-term hypoxia exposition (simulated altitude 9000 m) in young immature rats. Experiments were performed on freely moving 12-, 25- and 35-day-old male Wistar rats. One hour prior to hypoxia exposition, animals were pre-treated with melatonin and 24 hours after hypoxia cortical afterdischarges (ADs) were elicited by repeated stimulation of the right sensorimotor cortex. The duration of evoked ADs and shape of evoked graphoelements was monitored. Short-term exposure to hypoxic conditions resulted in significantly shorter ADs duration in 12-day-old rats after stimulations (except the 2nd one stimulation) compared to control group. Administration of melatonin prolonged the duration of ADs after all stimulations except the 1st one. Analysis of the duration ADs revealed no significant changes, either after the exposition to hypobaric hypoxia or after melatonin administration in 25- and 35-day-old animals. Effects and mechanisms of melatonin action on the brain seizure susceptibility and the possible beneficial role of that treatment in hypoxic brain damage are discussed.

Selective vulnerability of the hippocampus to the cytotoxic edema; magnetic resonance imaging and fluorescence microscopy studies in the rats.

OBJECTIVES: Changes in the hippocampus induced by water intoxication were studied using fluorescence microscopy (FM) and magnetic resonance imaging (MRI). METHODS: In three animals (rats), intracellular/extracellular distribution of Evans blue (EB) in cerebral cortex and hippocampus of both hemispheres was revealed by injection of EB into the internal carotid artery (ICA) in hyperhydrated rats (water intoxication, WI). A total of 8 experimental rats were used for the MRI study. The animals were scanned before WI, then the experimental brain edema was induced by WI and MR scanning was performed at day 1 and day 8 after WI. Besides standard T2-weighted imaging an apparent diffusion coefficient (ADC) and transverse relaxation time (T2) were evaluated. RESULTS: Hyperhydration brought about the largest intracellular deposits of EB in CA3 hippocampal region, followed by the cerebral cortex and CA1 hippocampal region with the lowest amount of intracellular EB in the dentate gyrus. A higher apparent diffusion coefficient (corresponding to a vasogenic edema) was found the first day after hyperhydration in the cortex and in the CA1 and CA3 regions with no changes in dentate gyrus. CONCLUSION: Both FM and MRI confirmed a selectively higher vulnerability to hyperhydration and hyponatremia (achieved by water intoxication) of the hippocampal cells compared to dentate gyrus cells.

Intracranial pressure and mean arterial pressure monitoring in freely moving rats via telemetry; pilot study.

OBJECTIVES: Accurate values of the intracranial pressure (ICP) and mean arterial pressure (MAP) are the prerequisite for calculating cerebral perfusion pressure (CPP). Increased ICP values decrease CPP. The origin of ICP increase in the clinical cases after brain ischemia and diffuse brain injury is the cellular brain edema (CE). Short-term monitoring of ICP and MAP is possible only in the unconscious patients, in experiments with rats it used to be possible only in general anesthesia. Long-term monitoring of ICP or MAP in the clinical practice is not possible. We therefore introduce an experimental model with telemetric monitoring. METHODS: ICP (subdurally) and MAP (intracarotically) were monitored in freely moving rats for 72 hours by DSI™ (Data Sciences International) telemetry system. The control group consisted of 8 rats, the experimental group had 8 animals with CE-induced by water intoxication. RESULTS: The mean MAP, ICP and CPP values were significantly higher in the experimental group. Average values of MAP were 19.9 mmHg (18%), ICP 5.3 mmHg (55%), CPP 14.5 mmHg (15% higher). CONCLUSION: The results of the pilot study verified possibilities of long-term telemetric monitoring of the mean arterial and intracranial pressures for the determination of current cerebral perfusion pressure in freely moving rats under physiological conditions and with increased intracranial pressure due to the induced cerebral edema. Detailed analysis of the course of the curves in the experimental group revealed episodes of short-term CPP reduction below the optimum value of 70 mmHg. Interpretation of these episodes requires simultaneous monitoring of rat behavior.

Cytotoxic brain edema induced by water intoxication and vasogenic brain edema induced by osmotic BBB disruption lead to distinct pattern of ICP elevation during telemetric monitoring in freely moving rats.

OBJECTIVES: A novel method of long-term telemetric monitoring of mean arterial pressure (MAP) and intracranial pressure (ICP) for the determination of current cerebral perfusion pressure (CPP) and the time course of ICP in freely moving rats under physiological conditions and with increased ICP due to the induced cerebral edema were studied. METHODS: The brain edema, that caused volume enlargement and ICP elevation was achieved in entirely experimental conditions without any parallel pathological process. Vasogenic/extracellular edema was induced by osmotic blood-brain barrier disruption (BBBd) and for induction of cytotoxic/intracellular edema the water intoxication model (WI) was used. RESULTS: The results showed significantly elevated values of ICP both in conditions of osmotic blood-brain barrier disruption (BBBd model) and cytotoxic/intracellular edema (WI model) compared to intact rats. The average values of ICP were significantly higher in WI model compared to osmotic BBBd model. Distinct pattern of elevated ICP, related to the selected way of experimental brain edema induction, was found. In the experimental model of osmotic BBB disruption, the elevation of ICP started earlier but was of very short duration. In WI model the elevation of ICP was present during the whole period of monitoring. CONCLUSION: Our results indicate that purely experimental models of brain edema (WI, BBBd) without any parallel pathological process can compromise the basic brain homeostatic activity.

New approach to the urogynecological ultrasound examination.

OBJECTIVE: To evaluate a new system for the ultrasound evaluation of urethral mobility. STUDY DESIGN: We studied the structure of interpubic disc and found landmarks that can be used to align different images and set up an universal system of coordinates. The method for capturing and post-processing of the introital ultrasound examination is described. The urethra in its entire course is evaluated. Ten patients were examined and some important points at the interpubic disc and the urethra were traced to assess the reproducibility of the method. RESULTS: The mean intra-observer difference for x and y coordinates were 1.88 mm (S.D. 1.53) and 2.00 mm (S.D. 1.54), respectively. The inter-observer difference was 2.30 mm (S.D. 1.64) and 2.50 mm (S.D. 1.79), respectively for x and y coordinates. CONCLUSION: The method shows good inter- and intra-observer correlation and presents data that can be further used for biomechanical analysis.