Jovan Savic

Ultrastructural and functional characteristics of blast injury-induced neurotrauma.

OBJECTIVE The present study investigates whether whole-body or local (chest) exposure to blast overpressure can induce ultrastructural, biochemical, and cognitive impairments in the brain. METHODS Male Wistar rats were trained for an active avoidance task for 6 days. On day 6, rats that had acquired the avoidance response were subjected to whole-body blast injury (WBBI), generated by large-scale shock tube (n = 40); or local (chest) blast injury (LBI), induced by blast overpressure focused on the right middle thoracic region and generated by small-scale shock tube (n = 40) while the heads of animals were protected. At the completion of cognitive testing, rats were killed at 3 hours, 24 hours, and 5 days after injury. Ultrastructural changes in the hippocampus were analyzed electron microscopically. Parameters of oxidative stress (malondialdehyde and superoxide anion generation) and antioxidant enzyme defense (superoxide dismutase and glutathione peroxidase activity) were measured in the hippocampus to assess biochemical changes in the brain after blast. RESULTS Ultrastructural findings in animals subjected to WBBI or LBI demonstrated swellings of neurons, glial reaction, and myelin debris in the hippocampus. All rats revealed significant deficits in performance of the active avoidance task 3 hours after injury, but deficits persisted up to day 5 after injury only in rats subjected to WBBI. Oxidative stress development and altered antioxidant enzyme defense was observed in animals in both groups. Cognitive impairment and biochemical changes in the hippocampus were significantly correlated with blast injury severity in both WBBI and LBI groups. CONCLUSION These results confirm that exposure to blast overpressure induces ultrastructural and biochemical impairments in the brain hippocampus, with associated development of cognitive deficits.

Blast injury from explosive munitions.

OBJECTIVE To evaluate the effect of blast in common war injuries. METHODS One thousand three hundred and three patients injured by explosive munitions and demonstrating extremity wounds without other penetrating injuries were admitted to the Military Medical Academy in Belgrade between 1991 and 1994. Of these, 665 patients (51%) had symptoms and physical signs that were compatible with the clinical diagnosis of primary blast injury, whereas the remaining 658 patients did not. RESULTS Random sampling of 65 patients in the blast group during the early posttraumatic period showed statistically significant elevations in blood thromboxane A2 (TxA2), prostacyclin (PGI2), and sulfidopeptide leukotrienes compared with the random sample of 62 patients in the nonblast group. This difference could not be accounted for by differing injury severity between the groups, because the severity of wounds as measured by both the Injury Severity Score and the Red Cross Wound Classification was similar in both groups. Amongst blast patients, 200 patients (30%) had long-term (1 year) symptoms and signs reflecting central nervous system disorders. These symptoms and signs were only sporadically found in 4% of the nonblast patients. These findings indicate that primary blast injury is more common in war injuries than previously thought and that of those affected by blast, a surprisingly high proportion retain long-term neurologic disability. The elevation in eicosanoids could be used to confirm and monitor blast injury. CONCLUSION In relation to the immediate management of patients injured by explosive weapons, it follows that particular attention should be paid to the presence and/or development of blast injury. Our findings indicate that blast is more common in war injuries than previously thought. Eicosanoid changes after blast injury suggest that blast injury causes a major physiologic stress. A variety of effects on the central nervous system suggest that blast injury could be responsible for some aspects of what is now considered to be the posttraumatic stress disorder.

Cognitive deficits following blast injury-induced neurotrauma: possible involvement of nitric oxide

Blast injuries, that is injuries caused by the complex pressure wave generated by some explosions, show increasing frequency throughout the world. However, whether blast injury is capable of inducing memory dysfunction has not been previously investigated. The present study examines the effects of blast injury-induced neurotrauma on memory deficit in rats. Furthermore, it is hypothesized that blast injury, stimulating nitric oxide production in the medial mesodiencephalic reticular formation and the dorsal hippocampus, both structures being involved in memory processing, may induce memory deficits. Prior to blast injury, Wistar rats were trained for an active avoidance task for 6 days. On day 6, rats that had acquired the avoidance response were subjected to whole-body blast injury, using a BT-I shock tube. Neurotrauma was confirmed by electron microscopical examination. At the completion of cognitive testing, rats were sacrificed at 3, 24 hours and 5 days after injury. The nitric oxide production in the brain structures was determined by the total nitrite/nitrate concentration, and by the expression of inducible nitric oxide synthase mRNA. The rats with blast injury revealed significant deficits in performance of the active avoidance task that persisted up to 5 days post-injury. Electron microscopical findings in both brain structures showed swellings of neurons, glial reaction, myelin debris, and increased pinocytotic activity on the fifth day following trauma. In blast injured rats, there was a significant elevation in total nitrite/nitrate levels 3 and 24 hours following injury which was comparable with the changes in the expression of inducible nitric oxide synthase mRNA. The results indicate that blast injury-induced neurotrauma is able to cause cognitive deficits.Blast injuries, that is injuries caused by the complex pressure wave generated by some explosions, show increasing frequency throughout the world. However, whether blast injury is capable of inducing memory dysfunction has not been previously investigated. The present study examines the effects of blast injury-induced neurotrauma on memory deficit in rats. Furthermore, it is hypothesized that blast injury, stimulating nitric oxide production in the medial mesodiencephalic reticular formation and the dorsal hippocampus, both structures being involved in memory processing, may induce memory deficits. Prior to blast injury, Wistar rats were trained for an active avoidance task for 6 days. On day 6, rats that had acquired the avoidance response were subjected to whole-body blast injury, using a BT-I shock tube. Neurotrauma was confirmed by electron microscopical examination. At the completion of cognitive testing, rats were sacrificed at 3, 24 hours and 5 days after injury. The nitric oxide production in the brain structures was determined by the total nitrite/nitrate concentration, and by the expression of inducible nitric oxide synthase mRNA. The rats with blast injury revealed significant deficits in performance of the active avoidance task that persisted up to 5 days post-injury. Electron microscopical findings in both brain structures showed swellings of neurons, glial reaction, myelin debris, and increased pinocytotic activity on the fifth day following trauma. In blast injured rats, there was a significant elevation in total nitrite/nitrate levels 3 and 24 hours following injury which was comparable with the changes in the expression of inducible nitric oxide synthase mRNA. The results indicate that blast injury-induced neurotrauma is able to cause cognitive deficits.

Involvement of the central nervous system in the general response to pulmonary blast injury.

The local, general, and cerebral responses of rabbits exposed to pulmonary blasts were examined to define the role of vagal afferentation in cardiorespiratory as well as metabolic control after a blast injury. Two series of experiments were conducted on rabbits to analyze the general, local, and cerebral responses to pulmonary injury caused by blast overpressure, and to evaluate the effects of bilateral vagotomy on the general, local, and cerebral responses to local (pulmonary) blast injury. The blast wave was generated in laboratory conditions using an air-driven shock tube that was able to cause moderate pulmonary blast injury, i.e., four pulmonary contusions characterized as confluent ecchymoses involving 30 to 60% of the lungs. One group of animals was subjected to pulmonary deafferentation, performed by bilateral transections of the vagus, glossopharyngeal, and hypoglossal nerves. Numerous hemodynamic as well as biochemical parameters were observed in systemic circulation and in lung and brain (medulla oblongata) tissues. After observation during the early posttraumatic period, rabbits were sacrificed by decapitation 30 minutes after the blast injury. On the basis of obtained results, it was concluded that vagal afferents have an important role in the modification of general and local responses to a pulmonary blast injury. Furthermore, it was suggested that functional changes in medulla oblongata may be the consequences of afferent neural impulses from the injured region (lungs) rather than consequences of ischemia, energy transfer to the brain, or both.

Relations among Plasma Prolactin, Testosterone, and Injury Severity in War Casualties

Abstract. Tissue trauma leads to a complex hormonal response of pituitary end-organ axis. This response can be recorded by determining parameters that represent the functional integrity of these systems. The concentrations of serum prolactin (PRL), serum testosterone, and plasma adrenocorticotropin (ACTH) were measured in 62 adult male casualties from the recent war in former Yugoslavia. Patients with brain injury were not included. Venous blood samples were taken as soon as possible (2–18 hours) after admission and at 1, 2, 5, and 14 days after injury. The severity of gunshot/missile wounds was assessed by the Injury Severity Score (ISS). The control group consisted of healthy blood donors. Uninjured subjects who had undergone great stress on the battlefield (explosion in the vicinity without injury) served as the sham-control group. Tissue trauma leads to a severity-dependent decrease in serum testosterone concentrations during the first 5 days following injury. Significant correlations were observed between ACTH, prolactin, and ISS during the first 18 hours after injury. A strong negative correlation between testosterone and prolactin serum concentrations was found during the first 18 hours. In patients with additional complications or unsatisfactory outcome, the prolactin concentrations remained elevated, whereas testosterone concentrations were reduced. Our results support the usefulness of recording hormonal changes for determining trauma severity and monitoring the clinical course. Such monitoring also helps assess the efficacy of therapeutic strategies. The relation between testosterone and prolactin might be helpful for predicting the clinical course and trauma outcome.

Early plasma amino acid pool alterations in patients with military gunshot/missile wounds.

Plasma amino acid profiles in patients during the early period (first 18 hours) following military gunshot/missile wounds were investigated. Patients (n = 29) were casualties from the war in the former Yugoslavia with injury severity scores ranging from 4 to 18. They were divided into three groups: soft tissue (muscle) damage, wounds with fractures, and vital structures injured. Controls were normal blood donors (n = 17). Free amino acids were analyzed in venous plasma. Increased concentrations of phenylalanine and glutamine associated with increased molar phenylalanine/tyrosine ratio in plasma indicated increased net protein catabolism in the peripheral tissues, regardless of the type of injured tissues. Decreased plasma arginine, ornithine and citrulline levels, accompanied with increased molar glutamine/valine ratio, suggested disturbance in urea cycle activity, although urea level was not altered. We concluded that early changes in plasma amino acid pool characteristics after wounds were of systemic origin, not related to the type of injured tissues.

Transmitter interactions in the central cholinergic control of blood pressure regulation.

There are at least five mechanisms by which the central nervous system regulates neural and humoral systems that control the blood pressure (BP). Particular attention has been paid to central cholinergic-adrenergic interactions in the regulation of BP. Physostigmine and other anticholinesterases which penetrate the blood-brain barrier, both carbamates and organophosphates, produce an increase of BP. This effect can be abolished by atropine, but not by methylatropine. The available evidence indicates that physostigmine and other AChE inhibitors initially produce an activation of central muscarinic receptors, which subsequently leads to an increase of the peripheral adrenergic activity. The hypertensive response to physostigmine is possible only if a functionally competent ChE is present in the brain. This effect of physostigmine is regularly associated with a dose-related increase in the neural activity in the preganglionic fibers of the cervical sympathetic nerve. BP rise after physostigmine is significantly less in immunosympathectomized animals and almost completely abolished after chemical sympathectomy. Physostigmine significantly increased the plasma concentration of catecholamines. After electrocoagulation of the locus coeruleus, not only did a significant decrease occur in the basic level of noradrenaline in plasma, but there was also a strong depression of the noradrenaline plasma response to physostigmine and immobilization. Physostigmine increased lipolysis and glycogenolysis, whereas neostigmine did not produce any change. Several directly acting cholinergic agonists alter the functions of the cardiovascular system when injected directly into the cerebral ventricular system, or directly into various brain regions. The most probable sites of action of AChE inhibitors and directly acting cholinergic agonists are the locus coeruleus, the nucleus tractus solitarii and the rostral ventrolateral medulla (RVLM). The primary activation of the cholinergic synapse is believed to take place in RVLM. Met-enkephalin, Leu-enkephalin and beta-endorphin, when applied exogenously, depress or even abolish the hypertensive effect of physostigmine. The same type of response was obtained after application of substances which inhibit the enkephalin-degrading enzymes (bestatin, phosphoramidon). Thus, the exogenous or endogenous enkephalins activate the opioid receptors in the brain and at the same time produce a depression of the cholinergic-adrenergic interaction in the central nervous system, which is a prerequisite for the hypertensive response to physostigmine. The functional role of the central cholinergic mechanisms in BP control under physiological conditions has not been established with certainty. These mechanisms might have a more significant role under pathological or homeostatic disturbances. For example, physostigmine showed a life-saving effect in acute hypovolemic shock in rabbits.

Leukotrienes in the pathogenesis of pulmonary blast injury.

Our previous studies demonstrate a significant increase of sulfidopeptide leukotriene concentrations in animals exposed to a free air blast. The aim of this study was to analyze the role of leukotrienes in the local response of lung tissue as well as in the general response of organisms to blast overpressure. The study was conducted on adult rabbits exposed to moderate blast overpressure (four pulmonary contusions characterized as confluent ecchymoses involving 30 to 60% of the lungs), generated in laboratory conditions. One group of experimental animals was treated with 5-lipoxygenase (5-LO) inhibitor, diethylcarbamazine (DEC, Sigma, St. Louis, Missouri) (50 mg/kg, i.v.), immediately before blast. The early posttraumatic period was observed (30 minutes after blast). Hemodynamic parameters (mean arterial pressure, heart rate, blood gases) as well as arterial plasma levels of conjugated dienes were observed. The myeloperoxidase activity, lipid peroxidation products levels, and water contents were measured in the lung tissue of injured rabbits. We observed that 5-LO inhibition reduced edema formation, accumulation of neutrophils, and generation of lipid peroxidation products in injured lungs. In this study, we demonstrated that treatment with DEC inhibits the increased systemic generation of conjugated dienes after blast injury. Although DEC exerts local antioxidant activity with beneficial effects on lung tissue, this 5-LO inhibitor intensifies the blast overpressure caused hemodynamic insufficiency.

The Cardiovascular Effects of the Administration of l-NAME during the Early Posthemorrhagic Period

1. The effects of the various doses of NG-nitro-L-arginine methyl ester (L-NAME, 10 and 30 mg/kg) on some cardiovascular and biochemical parameters during the early posthemorrhagic period were studied in anesthetized rabbits subjected to hemorrhagic hypovolemia. 2. Hemorrhagic shock was produced by intermittent bleeding of 40% of the estimated blood volume for 15 min. Blood samples were taken before and after bleeding (0, 15 and 60 min). Simultaneously, the mean arterial pressure (MAP) and the heart rate (HR) were measured. Hemorrhaged rabbits were treated by L-NAME10 or L-NAME30 (10 or 30 mg/kg, i.v. bolus injection, respectively) or the corresponding volumes of saline (0.6 ml, i.v. bolus) immediately after the end of bleeding. 3. The observed cardiovascular parameters (MAP, HR) were significantly reduced after the end of bleeding in all rabbits. 4. The rise of the MAP was significantly more pronounced 30 min after the injection of L-NAME30 in comparison with the corresponding values in the saline (S) group. In contrast, L-NAME10 produced only a small, insignificant increase in the MAP in hemorrhaged rabbits. 5. The L-NAME30-induced rise of the MAP was accompanied by a severe bradycardia, hyperkalemia and an aggravated metabolic acidosis, more severe than the corresponding disturbance of the acid-base status in the S group. The changes in the acid-base parameters were observed both in arterial (pH, excess base) and in venous blood (pH) of hemorrhaged rabbits. 6. In conclusion, the i.v. bolus injection of L-NAME30 (immediately after the end of bleeding) produced a significant increase in the MAP during the first hour after the injury, but the presumable inhibition of the endothelial constitutive nitric oxide synthase during the early posthemorrhagic period resulted in severe cardiovascular and metabolic disturbances.

The effect of physostigmine on acid-base status in arterial and venous blood of anaesthetized rabbits following hypovolemic shock

1. The effects of physostigmine (70 micrograms kg-1, intravenously) on acid-base status in arterial and venous blood were studied in anaesthetized rabbits subjected to hemorrhagic hypovolemia. 2. Hemorrhagic shock was produced using intermittent bleeding of 50% of the estimated blood volume, during 30 min. Experimental group was treated with physostigmine (70 micrograms kg-1 body mass, intravenously) and the control group with the same volume (0.1 ml) of saline, immediately after bleeding. Blood samples were taken before and after bleeding (0, 15 and 60 min). 3. It was found that physostigmine increased the mean arterial blood pressure, did not change the heart rate, and improved survival of the animals. 4. These effects of physostigmine were associated with significant decrease in venous pH, produced mainly by increased PCO2. This can partly be explained in terms of additional vasoconstriction due to physostigmine action. 5. In arterial blood decreased pH, decreased standard bicarbonate, negative values of excess base and decreased PCO2 were observed both in physostigmine-treated and the control group of animals, indicating partly respiratory compensated metabolic acidosis. These findings indicate that the hypertensive effect of physostigmine in shock was not accompanied by more severe disturbance in arterial acid-base status than was observed in hypovolemic shock alone.