Brain protection: physiological and pharmacological considerations. Part I: The physiology of brain injury

Guidance for the use and reporting of anaesthetic agents in BJP manuscripts involving work with animals

Scientists who plan to publish in the British Journal of Pharmacology (BJP) should read this article before undertaking studies utilising anaesthetics in mammalian animals. This editorial identifies certain gaps in the reporting of details on the use of anaesthetics in animal research studies published in the BJP. The editorial also provides guidance, based upon current best practices, for performing in vivo experiments that require anaesthesia. In addition, mechanisms of action and physiological impact of specific anaesthetic agents are discussed. Our goal is to identify best practices and to provide guidance on the information required for manuscripts submitted to the BJP that involve the use of anaesthetic agents in studies with experimental animals.

M, Siva Sankar Reddy L, Dastagiri Reddy Y, Somasekhar G, Sirisha N, Nagaraju K, Shouib M, Rizwaan A. A new cerebral ischemic injury model in rats, preventive effect of gallic acid and in silico approaches

Current study was designed multiple occlusions and reperfusion of bilateral carotid arteries induced cerebral injury model and evaluated the protective effect of gallic acid on it. In silico study was involved to study gallic acid binding affinity on cerebrotonic proteins compared with standard drugs using Autodoc vina tool. Cerebral ischemia was induced by occlusion of bilateral common carotid arteries for 10 mins followed by 10 reperfusions (1 cycle), cycle was continued to 3 cycles (MO/RCA), then pathological changes were observed by estimation of brain antioxidants as superoxide dismutase, glutathione, catalase, oxidants like malonaldehyde, cerebral infarction area, histopathology, and study gallic acid treatment against cerebral injury. Gallic acid exhibited a strong binding affinity on targeted cerebrotoxic proteins. MO/RCA rat brain antioxidant levels were significantly decreased and increased MDA levels (p < 0.0001), Infarction size compared to sham rats. Gallic acid treatment rat brain MDA levels significantly decreased (p < 0.4476) and increased SOD (p < 0.0001), CAT (p < 0.0001), GSH (p < 0.0001), cerebral infarction area when compared to MO/RCA group. Developed model showed significant cerebral ischemic injury in rats, injury was ameliorated by Gallic acid treatment and in silico approaches also inhibit the cerebrotoxic protein function by targeting on active sites.

Avoiding use of total circulatory arrest in the practice of congenital heart surgery

Deep hypothermic circulatory arrest (DHCA) technique has been an important armamentarium in the correction of congenital heart diseases. There have been many controversies and concerns associated with DHCA, particularly neurological damage. Selective ante grade cerebral perfusion (SACP) was introduced as an adjunct to DHCA with the objective of limiting the neurologic injury during aortic arch repairs. Over the past two decades, various aspects of cardiopulmonary bypass and DHCA have been studied and modified such as optimisation of flows, anti-inflammatory interventions, haematocrit, and temperature to improve neurologic outcomes. With the changes in practice of DHCA, outcomes have significantly improved but SACP intuitively appears attractive to offer better neuroprotection. The strategy of conduct of SACP is evolving and needs to be standardised for comparing outcomes. In this review we have discussed the various physiological and technical factors involved in conduct of SACP in paediatric cardiac surgery and outcomes with SACP.

Neuroprotective effect of Convolvulus pluricaulis Choisy in oxidative stress model of cerebral ischemia reperfusion injury and assessment of MAP2 in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Convolvulus pluricaulis Choisy commonly known as Shankhapushpi, is traditionally prescribed for nerve debility, loss of memory, epilepsy and as nervine tonic. Plant also proved to have diverse pharmacological activity but the neuroprotection in ischemic stroke were not found.

AIM OF THE STUDY

To investigate the effect of Convolvulus pluricaulis against bilateral common carotid artery (BCCA) occlusion induced cerebral ischemic reperfusion injury.

MATERIALS AND METHODS

The neuroprotective activity of Convolvulus pluricaulis against bilateral common carotid artery (BCCA) occlusion induced cerebral ischemic reperfusion (I/S) injury. Sprague-Dawley rats of either sex (200-250 g) were divided into nine groups of 8 rats each. Sham and control group, saline treated 10 ml/kg orally. Third group treated with Quercetin 25 mg/kg orally and fourth to ninth groups treated with chloroform and ethanol extract of Convolvulus pluricaulis 100, 200, and 400 mg/kg (p.o.) respectively. Control, Quercetin and extract treated groups underwent 30 min BCCA occlusion and 24 h reperfusion on 10th day but sham underwent same surgery without BCCA occlusion and 24 h reperfusion on 10th day. The antioxidant enzymatic and non-enzymatic levels were estimated by UV spectroscopic method and cerebral infarction area, Blood brain barrier disruption, microtubule-associated protein 2 immunohistochemical and histopathological studies were carried out.

RESULTS

The results of the study indicate that the chloroform and ethanol extract of Convolvulus pluricaulis showed neuroprotective activity by a significant decrease in lipid peroxidation (p < 0.001) and an increase in superoxide dismutase (p < 0.01, p < 0.001), catalase (p < 0.01, p < 0.001), glutathione (p < 0.001), and total thiol (p < 0.001) levels in extract-treated groups as compared to control group. Measurement of cerebral infarction area, blood brain barrier disruption, microtubule-associated protein 2 immunohistochemical and histopathological studies further supported the protective effect of the extract.

CONCLUSIONS

Present study revile that Convolvulus pluricaulis has potent neuroprotection against bilateral common carotid artery (BCCA) occlusion induced cerebral ischemic reperfusion injury.

An Extremely Low Frequency Magnetic Field and Global Cerebral Ischemia Affect Pituitary ACTH and TSH Cells in Gerbils

The neuroendocrine system can be modulated by a magnetic field and cerebral ischemia as external and internal stressors, respectively. This study deals with the separate or combined effects of an extremely low frequency (ELF) magnetic field (50 Hz, average magnetic field of 0.5 mT) for 7 days and global cerebral ischemia for 10 min on the morpho-functional features of pituitary adrenocorticotrophic (ACTH) and thyrotrophic (TSH) cells in 3-month-old gerbils. To determine the immediate and delayed effects of the applied stressors, measurements were made on the 7th and 14th days after the onset of the experiment. The ELF magnetic field and 10-min global cerebral ischemia, separately and particularly in combination, decreased (P < 0.05) the volume density of ACTH cells, while only in combination were intracellular ACTH content and plasma ACTH concentration increased (P < 0.05) on day 7. The ELF magnetic field elevated serum TSH concentration on day 7 and intracellular TSHβ content on day 14 (P < 0.05). Also, 10-min global cerebral ischemia alone increased serum TSH concentration (P < 0.05), while in combination with the ELF magnetic field it elevated (P < 0.05) intracellular TSHβ content on day 14. In conclusion, an ELF magnetic field and/or 10-min global cerebral ischemia can induce immediate and delayed stimulation of ACTH and TSH synthesis and secretion. Bioelectromagnetics. 2020;41:91-103. © 2019 Bioelectromagnetics Society.

Spectral Content of Electroencephalographic Burst-Suppression Patterns May Reflect Neuronal Recovery in Comatose Post-Cardiac Arrest Patients

PURPOSE

To assess the potential biologic significance of variations in burst-suppression patterns (BSPs) after cardiac arrest in relation to recovery of consciousness. In the context of recent theoretical models of BSP, bursting frequency may be representative of underlying network dynamics; discontinuous activation of membrane potential during impaired cellular energetics may promote neuronal rescue.

METHODS

We reviewed a database of 73 comatose post-cardiac arrest patients who underwent therapeutic hypothermia to assess for the presence of BSP and clinical outcomes. In a subsample of patients with BSP (n = 14), spectral content of burst and suppression periods were quantified using multitaper method.

RESULTS

Burst-suppression pattern was seen in 45/73 (61%) patients. Comparable numbers of patients with (31.1%) and without (35.7%) BSP regained consciousness by the time of hospital discharge. In addition, in two unique cases, BSP initially resolved and then spontaneously reemerged after completion of therapeutic hypothermia and cessation of sedative medications. Both patients recovered consciousness. Spectral analysis of bursts in all patients regaining consciousness (n = 6) showed a prominent theta frequency (5-7 Hz) feature, but not in age-matched patients with induced BSP who did not recover consciousness (n = 8).

CONCLUSIONS

The prognostic implications of BSP after hypoxic brain injury may vary based on the intrinsic properties of the underlying brain state itself. The presence of theta activity within bursts may index potential viability of neuronal networks underlying recovery of consciousness; emergence of spontaneous BSP in some cases may indicate an innate neuroprotective mechanism. This study highlights the need for better characterization of various BSP patterns after cardiac arrest.

Homeostatic dynamics, hysteresis and synchronization in a low-dimensional model of burst suppression

Burst suppression, a pattern of the electroencephalogram characterized by quasi-periodic alternation of high-voltage activity (burst) and isoelectric silence (suppression), is typically associated with states of unconsciousness, such as in deep general anesthesia and certain etiologies of coma. Recent computational models for burst suppression have attributed the slow (up to tens of seconds) time-scale of burst termination and re-initiation to cycling in supportive physiological process, such as cerebral metabolism. That is, activity-dependent substrate ('energy') depletion during bursts, followed by substrate recovery during suppression. Such a model falls into the category of a fast-slow dynamical system, commonly used to describe neuronal bursting more generally. Here, following this basic paradigm, we develop a low dimensional mean field model for burst suppression that adds several new features and capabilities to previous models. Most notably, this new model includes explicit homeostatic interactions wherein the rates of substrate recovery are tied to neuronal activity in a supply demand loop, creating a physiologically consistent, reciprocal interaction between the neural and substrate processes. We develop formal analysis of the model dynamics, showing, in particular, the capability of the model to produce burst-like activity as a consequence of neuronal downregulation only, without any direct perturbation to the substrate dynamics. Further, we use a synchronization analysis to contrast different mechanisms for spatially local versus global bursting. The analysis performed generates characterizations that are consistent with experimental observations of spatiotemporal features such as burst onset, duration, and spatial organization and, moreover, generates predictions regarding the presence of bistability and hysteresis in the underlying system. Thus, the model provides new dynamical insight into the mechanisms of burst suppression and, moreover, a tractable platform for more detailed future characterizations.

Effects of Danhong Injection (丹红注射液) and its main components on anticoagulation and fibrinolysis in cultured vein endothelial cells

OBJECTIVE

To observe the effects of Danhong Injection (丹红注射液) and its main components, including daiclzein and hydroxysafflor yellow A (HSYA), on the anticoagulation, fibrinolysis, anti-apoptosis in hypoxia model of vein endothelial cells (VECs).

METHODS

VECs were prepared and were put in a hypoxia environment, which consisted of mixed gas of 95% N and 5% CO mixed gas, when reached confluent culture. Five groups used different treatments, including normal control group, hypoxia group, daiclzein group, HSYA group and Danhong Injection group. The VECs were identified by fluorescence double labeling methods. The morphology was observed by a phase contrast microscopy. The effects of Danhong Injection, daiclzein and HSYA on 6 keto prostaglandin F1α (6-keto-PGF1α) level was measured by the method of radioimmunoassay (RIA). Superoxide dismutase (SOD) activity was tested by water soluble tetrazolium salt. The content of malondialdehyde (MDA) was measured by thiobarbituric acid. The activities of tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI) were measured by the method of chromogenic substrate. The contents of endothelin (ET) and nitric oxide (NO) were detected by non-equilibrium RIA and enzymelinked immunosorbent assay. Cells apoptosis rate was determined by flow cytometry.

RESULTS

Compared with the normal control group, the floating cells number, PAI activity, ET and MDA contents, and cells apoptosis rate in the culture solution of hypoxia group were all significantly increased, whereas the 6-keto-PGF1α and NO contents, and t-PA and SOD activities were decreased significantly (P<0.01). Compared with the hypoxia group, Danhong Injection markedly increased the 6-keto-PGF1α content and SOD activity, regulated PAI and t-PA activities, ET and NO contents, and decreased MDA content and cells apoptosis rate (P<0.05 or P<0.01).

CONCLUSIONS

Danhong Injection and its main components played an important role in protecting primary VECs from hypoxic damage by regulating the secretion and vasomotor function of VECs. The function of Danhong Injection was most remarkable.

A mean field model for neural-metabolic homeostatic coupling in burst suppression

Burst suppression is an inactivated brain state in which the electroencephalogram is characterized by intermittent periods of isoelectric quiescence. Recent modeling studies have suggested an important role for brain metabolic processes in governing the very slow time scales that underlie the duration of bursts and suppressions. In these models, a reduction in metabolism leads to substrate depletion and consequent suppression of action potential firing. Such a mechanism accounts for the appearance of burst suppression when metabolism is directly down-regulated. However, in many cases such as general anesthesia, metabolic down-regulation occurs in part as a homeostatic consequence of reduced neuronal activity. Here, we develop a mean-field model for neuronal activity with metabolic homeostatic mechanisms. We show that with such mechanisms, a simple reduction in neuronal activity due, for example, to increased neuronal inhibition, will give rise to bistability due to a bifurcation in the combined neuronal and metabolic dynamics. The model reconciles a purely metabolic mechanism for burst suppression with one that includes important dynamical feedback from the neuronal activity itself. The resulting fast-slow dynamical description forms a useful model for further development of novel methods for managing burst suppression clinically.

Protective effect of Danhong injection on cerebral ischemia-reperfusion injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Danhong injection (DH), a Chinese medical product, is used extensively for the treatment of cerebrovascular diseases such as acutely cerebral infarction in clinic.

AIM OF THE STUDY

To explore the protective effect and the relevant mechanisms of DH on cerebral ischemia-reperfusion (I/R) injury.

MATERIALS AND METHODS

Cerebral I/R injury was induced through four-vessel occlusion (4-VO) or middle cerebral artery occlusion (MCAO). Adult male SD rats were randomly divided into six kinds of groups: normal control group, sham-operated group, I/R injury group, DH-treated groups at doses of 0.5ml/kg, 1.0ml/kg and 2.0ml/kg. The effects of DH on murine neurological deficits and cerebral infarct volume, 6-keto-prostagladin F(1α) (6-keto-PGF(1α)) level, malondialdehyde (MDA) level and superoxide dismutase (SOD) activity in brain tissue, as well as the activities of plasma tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI) after I/R were evaluated. Moreover, the expressions of Bcl-2 and Bax protein were detected by immunohistochemistry.

RESULTS

There was no significant difference between the control group and the sham-operated group based on the measurement indicators. Compared with the vehicle-treated group, rats treated with DH showed dose dependent reductions in brain infarction size, and improvement of neurological outcome. The level of 6-keto-PGF(1α) and the activities of SOD and plasma t-PA were enhanced significantly, whereas the level of MDA and the activity of plasma PAI were declined significantly. The immunohistochemical staining results also revealed that the expression of Bcl-2 protein was up-regulated and that of Bax protein was down-regulated when exposed to DH.

CONCLUSION

DH demonstrates a strong ameliorative effect on cerebral I/R damage in rats by its anticoagulant, antithrombotic, antifibrinolytic and antioxidant activities. Furthermore, suppressing apoptosis through regulating Bcl-2 and Bax protein expressions should be another potential mechanism by which DH exerts its neuroprotective function.

Response of hippocampal neurons and glial cells to alternating magnetic field in gerbils submitted to global cerebral ischemia

The purpose of this study was to determine whether exposure to an extremely low-frequency magnetic field (ELF-MF, 50 Hz) affects the outcome of postischemic damage in the hippocampus of Mongolian gerbils. After 10-min bilateral carotid occlusion, the gerbils were continuously exposed to ELF-MF (average magnetic induction at the center of the cage was 0.5 mT) for 7 days. The impact of ELF-MF was estimated immediately (the 7th day after reperfusion) and 7 days after cessation of exposure (the 14th day after reperfusion) compared with ischemic gerbils without ELF-MF exposure. Applying stereological methods, histological evaluation of changes in the hippocampus was done for determining its volume, volume densities of degenerating neurons and astrocytes, as well as the number of microglial cells per unit area. ELF-MF per se did not induce any morphological changes, while 10-min global cerebral ischemia led to neuronal death, especially in CA1 region of the hippocampus, as expected. Ischemic gerbils exposed to ELF-MF had significantly a lower degree of cell loss in the examined structure and greater responses of astrocytes and microglial cells than postischemic gerbils without exposure on the seventh day after reperfusion (immediate effect of ELF-MF). Similar response was observed on the 14th day after reperfusion (delayed effect of ELF-MF); however, differences in measured parameters were low and insignificant. Applied ELF-MF has possible neuroprotective function in the hippocampus, as the most sensitive brain structure in the model of global cerebral ischemia, through reduction of neuronal death and activation of astrocytes and microglial cells.

A neurophysiological-metabolic model for burst suppression

Burst suppression is an electroencepholagram (EEG) pattern in which high-voltage activity alternates with isoelectric quiescence. It is characteristic of an inactivated brain and is commonly observed at deep levels of general anesthesia, hypothermia, and in pathological conditions such as coma and early infantile encephalopathy. We propose a unifying mechanism for burst suppression that accounts for all of these conditions. By constructing a biophysical computational model, we show how the prevailing features of burst suppression may arise through the interaction between neuronal dynamics and brain metabolism. In each condition, the model suggests that a decrease in cerebral metabolic rate, coupled with the stabilizing properties of ATP-gated potassium channels, leads to the characteristic epochs of suppression. Consequently, the model makes a number of specific predictions of experimental and clinical relevance.

Extremely low frequency magnetic field induced changes in motor behaviour of gerbils submitted to global cerebral ischemia

The purpose of this study was to evaluate behavioural effects of an extremely low frequency magnetic field (ELF-MF) in 3-month-old Mongolian gerbils submitted to global cerebral ischemia. After 10-min occlusion of both common carotid arteries, the gerbils were placed in the vicinity of an electromagnet and continuously exposed to ELF-MF (50Hz, 0.5mT) for 7 days. Their behaviour (locomotion, stereotypy, rotations, and immobility) was monitored on days 1, 2, 4, 7, and 14 after reperfusion for 60min in the open field. It was shown that the 10-min global cerebral ischemia per se induced a significant motor activity increase (locomotion, stereotypy and rotations), and consequently immobility decrease until day 4 after reperfusion, compared to control gerbils. Exposure to ELF-MF inhibited development of ischemia-induced motor hyperactivity during the whole period of registration, but significantly in the first 2 days after reperfusion, when the postischemic hyperactivity was most evident. Motor activity of these gerbils was still significantly increased compared to control ones, but only on day 1 after reperfusion. Our results revealed that the applied ELF-MF (50Hz, 0.5mT) decreased motor hyperactivity induced by the 10-min global cerebral ischemia, via modulation of the processes that underlie this behavioural response.

Neonatal Brain Protection and Deep Hypothermic Circulatory Arrest: Pathophysiology of Ischemic Neuronal Injury and Protective Strategies

Deep hypothermic circulatory arrest (DHCA) has been used for the past 50 years in the surgical repair of complex congenital cardiac malformations and operations involving the aortic arch; it enables the surgeon to achieve precise anatomical reconstructions by creating a bloodless operative field. Nevertheless, DHCA has been associated with immediate and late neurodevelopmental morbidities. This review provides an overview of the pathophysiology of neonatal hypoxic brain injury after DHCA, focusing on cellular mechanisms of necrosis, apoptosis, and glutamate excitotoxicity. Techniques and strategies in neonatal brain protection include hypothermia, acid base blood gas management during cooling, and pharmacologic interventions such as the use of volatile anesthetics. Surgical techniques consist of intermittent cerebral perfusion during periods of circulatory arrest and continuous regional brain perfusion.

Protective effect of triflusal and its main metabolite HTB in an in vitro model of anoxia-reoxygenation in rat brain slices: comparison with acetylsalicylic and salicylic acids

Triflusal is a fluorinated derivative of acetylsalicylic acid (ASA) with demonstrated antithrombotic activity. Recently, evidence for a neuroprotective effect has been obtained. The aim of this study was to compare the neuroprotective effects of the main metabolite of triflusal (2-hydroxy-4-trifluoromethylbenzoic acid, HTB) and the ASA metabolite salicylic acid (SA) in an in vitro model of anoxia-reoxygenation in rat brain slices. Rat brain slices (n=10 per group) were subjected to a period of anoxia followed by 180 min reoxygenation. We measured oxidative stress parameters (lipid peroxidation, glutathione system), prostaglandins (PGE(2)), nitric oxide pathway activity (NO) (nitrites+nitrates, constitutive and inducible NO synthase activity) and LDH efflux, a biochemical marker of cell death. Various concentrations (10, 100 and 1,000 microM) of triflusal, HTB, ASA or SA were tested. Triflusal at 10, 100 and 1,000 microM decreased LDH efflux in rat brain slices after anoxia/reoxygenation by 24%, 35% and 49% respectively. This effect was proportionately greater than that of ASA (0%, 13% and 32%). The results with HTB were similar to those with triflusal, whereas SA showed a greater protective effect than ASA (13%, 33% and 35%). The antioxidant effects of HTB and SA on the biochemical mechanisms of cell damage studied here were also greater than the effects of triflusal and ASA, a finding attributable mainly to the decrease in lipid peroxidation and to the ability of HTB to also increase glutathione levels. The triflusal metabolite reduced inducible NO synthase activity by 18%, 21% and 30%, whereas SA inhibited this activity by 9%, 17% and 23%. Triflusal and HTB led to greater increases in NO synthase than ASA or AS. In conclusion, the metabolite HTB plays an important role in the neuroprotective effect of triflusal, at least in the experimental model of anoxia-reoxygenation tested here.

Effects of triflusal on oxidative stress, prostaglandin production and nitric oxide pathway in a model of anoxia-reoxygenation in rat brain slices

Acetylsalicylic acid (ASA) is the most widely used drug in the prevention of ischemic vascular accidents, mainly because of its antithrombotic effect. Recently, evidence of a neuroprotective effect has appeared. The aim of this study was to evaluate the neuroprotective effect of triflusal, a fluorinated derivative of ASA, in a model of anoxia-reoxygenation in rat brain slices. Rats (n=10 per group) were treated for 7 days with 1, 10 or 50 mg/kg/day p.o. of triflusal or ASA or solvent (control group), then brain slices were obtained and subjected to a period of anoxia followed by 180 min of reoxygenation. We measured oxidative stress parameters (lipid peroxidation, glutathione system), prostaglandins (PGE(2)), nitric oxide pathway activity (NO) (nitrites+nitrates, constitutive and inducible NO synthase activity) and cell death (lactate dehydrogenase (LDH) efflux). Triflusal decreased cell death in rat brain slices subjected to reoxygenation after anoxia by 21%, 42% and 47% with 1, 10 and 50 mg/kg/day, respectively. This effect was proportionately greater than the effect of ASA (0%, 25% and 24%). The antioxidant effects of triflusal on the biochemical mechanisms of cell damage studied here were also greater than the effects of ASA: lipid peroxidation was reduced by 29%, 35% and 36% with triflusal, and 0%, 19% and 29% with ASA. Inducible NO synthase activity was reduced by 25%, 27% and 30% with triflusal, and 0%, 25% and 24% with ASA. Triflusal can be considered an alternative to ASA as a neuroprotective agent, at least in the experimental model of anoxia-reoxygenation used in the present study.

Antioxidant effect of acetylsalicylic and salicylic acid in rat brain slices subjected to hypoxia

Acetylsalicylic acid (ASA) reduces the incidence of ischemic stroke mainly through its antithrombotic action; however, it also has a direct neuroprotective effect. The present study was designed to evaluate the effect of ASA on oxidative stress and the activity of nitric oxide synthase (NOS) in an in vitro model of hypoxia in rat brain slices. Rat brain slices were perfused with nitrogen (hypoxia) for a maximum of 120 min, after which we measured lipid peroxidation, glutathione levels, glutathione-related enzyme activities, and constitutive nitric oxide synthase (cNOS) and inducible nitric oxide synthase (iNOS) activities. In brain tissue subjected to hypoxia, ASA reduced oxidative stress and iNOS activity (all increased by hypoxia), but only when used at higher concentrations. The effects of salicylic acid (SA) were similar but more intense than were those of ASA. After oral administration, the effect of SA was much greater than that of ASA, and the decrease in cell death with SA was seen much more clearly. In view of the greater effect of SA compared to ASA on changes in oxidative stress parameters in a model of hypoxia, and higher brain concentrations of SA when it is administered alone than when ASA is given (undetectable levels), we conclude that SA plays an important role in the cytoprotective effect in brain tissue after ASA administration.

Release of excitatory amino acids in the penumbra of a focal cortical necrosis

A cortical tissue necrosis from focal trauma expands between 30% and 300% from its initial size within 24 h, depending on the species studied. To shed light on the pathophysiological processes in the penumbra 1 zone after a focal cortical lesion, the release of excitatory amino acids into the traumatic penumbra zone 1 was measured throughout the entire period of necrosis expansion. A microdialysis probe was inserted at an oblique angle into the cortex of Sprague-Dawley rats 2 mm below the brain surface. One day later, a highly standardized cortical freezing lesion was induced at the brain cortex above the microdialysis probe. Dialysate was continuously collected prior to, during, and up to 24 h after trauma and analyzed for primary amino acids. In each animal, it was confirmed histologically that the tip of the microdialysis probe was localized in the gray matter in close proximity to the primary lesion. Following induction of the trauma, a statistically significant sharp increase of the dialysate level of aspartate, glutamate, glycine, and serine was observed. Thereafter, the dialysate levels of these amino acids returned to baseline levels without any further increase throughout the remaining observation period. This process ranged in time from a few minutes to a few hours. The level of alanine in the dialysate was essentially not altered throughout the experiment. Although the early post-traumatic increase of the excitatory neurotransmitters aspartate and glutamate may well contribute to the secondary lesion growth of a cortical necrosis after trauma, glutamate receptor targeted therapeutic intervention may be in view of these findings of limited use when initiated post trauma.

Increased plasma beta-hydroxybutyrate, preserved cerebral energy metabolism, and amelioration of brain damage during neonatal hypoxia ischemia with dexamethasone pretreatment

Dexamethasone (DEX) pretreatment has been shown to be neuroprotective in a neonatal rat model of hypoxia ischemia (HI). The exact mechanism of this neuroprotection is still unknown. This study used 31P nuclear magnetic resonance spectroscopy to monitor energy metabolism during a 3-h episode of HI in 7-d-old rat pups in one of two groups. The first group was pretreated with 0.1 mL saline (i.p.) and the second group was treated with 0.1 mL of 0.1mg/kg DEX (i.p.) 22 h before HI. Animals pretreated with DEX had elevated nucleoside triphosphate and phosphocreatine levels during HI when compared with controls. Saline-treated animals had significant decreases in nucleoside triphosphate and phosphocreatine and increases in inorganic phosphate over this same period. 31P nuclear magnetic resonance data unequivocally demonstrate preservation of energy metabolism during HI in neonatal rats pretreated with DEX. Animals pretreated with DEX had little or no brain damage following 3 h of HI when compared with matched controls, which experienced severe neuronal loss and cortical infarction. These same pretreated animals had an increase in blood beta-hydroxybutyrate levels before ischemia, suggesting an increase in ketone bodies, which is the neonate's primary energy source. Elevation of ketone bodies appears to be one of the mechanisms by which DEX pretreatment provides neuroprotection during HI in the neonatal rat.

Determination and clinical significance of plasma levels of prostaglandins in patients with acute brain injury

BACKGROUND

Models of brain injury in experimental animals have shown that the level of prostaglandins (PGs) is increased in damage brain tissue, and that PGs play an important role in secondary brain damage. Almost all previous studies of the relationship between PGs and brain injury have been carried out in animals. In the present study we show that the PGs change in humans with brain injury.

METHODS

The plasma levels of thromboxane B2, 6-Keto-PGF2alpha, prostaglandin F2alpha, and prostaglandin E2 were measured by radioimmunoassay on the 1st, 3rd, 7th, and 14th days after brain injury. The same measurements were made on a control group of 26 healthy volunteers.

RESULTS

The levels of all four PGs were elevated, most markedly in the first week, with levels remaining high in the second week in the severely injured. On the first day levels were, on average, three times those found in the controls, with a seven-fold rise in some of the severely injured patients. Dividing the patients into three groups according to outcome, it was found that if the PGs were markedly increased to begin with and remained high, death or permanent disability was likely. In the group with good outcome, the levels dropped steadily from the initial high levels. The T/K ratio was studied. It related closely to the severity of injury, being higher in more severe injuries and decreasing with recovery. In patients who did not recover, the ratio increased steadily to its highest value on the 7th day, and remained high at the 14th.

CONCLUSION

Changes in PGs levels were closely related to the brain injury severity and its outcome, and there was a marked disturbance of the levels of PGs, which therefore appears to be an important indicator of secondary brain damage.

Complement system in healthy term newborns: reference values in umbilical cord blood

Activation of the complement system occurs in several diseases. For reliable identification of complement activation in neonates, we establish reference ranges of several components in cord blood of healthy term newborns. For this study, cord blood samples were taken from 125 healthy term newborns. Concentrations of C1r, C2, C5, C7, Properdin, and factors D, H, and I were determined by single radial immunodiffusion. C3a and C5a were measured by specific EIA and complement function was measured by hemolytic assays. The results were expressed as 5th percentile, median, and 95th percentile. The following respective concentrations were found: C1r: 27, 47, 65 mg/l; C2: 12.0, 18.0, 24.0 mg/l; C5: 64, 92, 127 mg/l; C7: 32, 60, 89 mg/l; Properdin: 5.6, 9.7, 14.2 mg/l; factor D: 3.6, 5.2, 7.3 mg/l; factor H: 178, 234, 296 mg/l; and factor I: 15, 24, 32 mg/l. The functional activity of the whole complement system was 24%, 43%, 97% and for the alternative pathway 39%, 58%, 76%. The concentration of the activated split products C3a was 4, 65, 255 microg/l and of C5a, 0.11, 0.26, 1.19 microg/l. These reference values may be important for the detection of deficiencies of native complement proteins or perinatal processes leading to an activation of the complement system.

Complement and contact activation in term neonates after fetal acidosis

AIMS

To evaluate complement and contact activation after fetal acidosis.

METHODS

Fifteen term neonates with hypoxic-ischaemic encephalopathy after umbilical arterial pH < 7.10 were compared with 15 healthy neonates with umbilical arterial pH > 7.20. Determinations of the complement function and C1-inhibitor activity were performed as kinetic tests 22-28 hours after birth. C1q, C1-inhibitor, and factor B concentrations were determined by radial immunodiffusion and those of C3a, C5a, and factor XIIa by enzyme immunoabsorbent assay.

RESULTS

Median complement function (46 vs 73%), C1q (4.3 vs 9.1 mg/dl), and factor B (5.2 vs 7.7 mg/dl) decreased after fetal acidosis. The activated split products C3a (260 vs 185 micrograms/l), C5a (5.0 vs 0.6 micrograms/l), and factor XIIa (3.2 vs 1.3 micrograms/l) increased in the neonates after fetal acidosis. No differences were found in the concentration and activity of C1-inhibitor.

CONCLUSIONS

Complement and contact activation occurred in the newborns with hypoxic-ischaemic encephalopathy. Activation of these systems generates mediators which can trigger inflammation and tissue injury.

In vitro activation of complement and contact system by lactic acidosis

The activation of complement and contact systems occurs in reperfusion injuries with initial tissue hypoxia, and lactic acidosis such as mycardial infarction and birth asphyxia. The aim of our experiment was the formal proof of activation by sole lactic acidosis. Lactic acid was added to blood and plasma samples from 10 healthy volunteers. C5a and factor XIIa were measured by EIA after incubation at 37 degrees C for 1 h. Both concentrations increased (P < 0.0001 by Friedman analysis) in blood and plasma samples with increasing amount of added lactic acid. Lactic acidosis can activate C5 from the complement system and factor XII from the contact system directly, even in the absence of cellular components.

Acute stroke intervention with intraarterial urokinase infusion

PURPOSE

A preliminary evaluation of the efficacy and safety of treating patients with acute stroke with intraarterial urokinase infusions was performed.

PATIENTS AND METHODS

Twelve patients with acute stroke were treated within 8 hours of symptom onset (average, 5 hours). Thrombolysis was performed within the middle cerebral (n = 10), internal carotid (n = 1), and basilar (n = 1) arteries. Urokinase (160,000-500,000 IU) was infused through microcatheters placed into or adjacent to the thrombi.

RESULTS

Thrombolysis was angiographically successful in nine patients (75%), all of whom had long-term neurologic improvement. No or minimal neurologic deficits were present in six patients (50%). Thrombolysis failed in three patients (25%); one patient died and two developed severe permanent neurologic deficits. No hemorrhagic complications occurred.

CONCLUSION

Preliminary results suggest that intraarterial urokinase infusion may be effective and safe for treating patients with acute stroke. Potentially devastating neurologic damage was averted or lessened in nine patients (75%). No additional neurologic damage was caused by intervention in the remaining three patients (25%).

[Osmolality and brain]

A modification of serum osmolarity induces always movements of water across cell membranes and therefore variations of cell volume of all tissues, including brain. To avoid a severe cell dehydration or hyperhydration, the organism has several regulation means called osmoregulation. Cerebral osmoregulation is essential as the brain is contained in a unexpandable box. In comparison with other organs, this phenomenon is complex and particular as: 1) cerebral volume consists of 3 sub spaces (intracellular, extracellular and cerebrospinal fluid [CSF]); 2) exists a blood-brain barrier (BBB) which behaves functionally as a semi-permeable membrane, essentially sensitive to osmolar disturbances. This brain volume regulation mechanism is working whatever the nature of the solutes initiating the osmotic deviation (sodium, glucose, mannitol...). Cerebral osmoregulation results from intracerebral osmolar modifications. Thus, every variation of plasma osmolarity elicits a similar variation of intracerebral osmolarity. This phenomenon results from modifications of the brain cell "protective" osmoles content. When the osmolar disturbance occurs quickly (in a few hours), cerebral osmoregulation is not complete. It results essentially from modifications of brain cell inorganic solutes content, i.e. electrolytes (Na, K, Cl) which originate from plasma, CSF and extracellular brain spaces uptake. When the osmolar disturbance is more progressive, cerebral osmoregulation is complete. The brain volume returns then to its initial value, by increasing its brain cell electrolytes, but above all organic "idiogenic" osmoles content. These idiogenic osmoles are identified as amino acids, polyols and trimethylamines. During treatment, the delayed normalization of brain osmolarity compared with plasma osmolarity prescribes a slow correction of the osmolar disturbance, as much as it is a chronic one.

Influence of nicardipine on post-hypoxic injury in the isolated perfused rat liver

We investigated microcirculatory changes and hepatocellular injury due to hypoxia/reoxygenation and the effects of nicardipine, a calcium channel blocker, using the isolated perfused rat liver technique. Liver perfusion was carried out in three consecutive phases: 30-min pre-hypoxia perfusion, 120-min hypoxia perfusion and 30-min reoxygenation perfusion in two groups, a control (n = 5) group and a nicardipine group (n = 5). In the nicardipine group, nicardipine (2 x 10(-6) M) was added to the perfusate prior to the hypoxia perfusion. Intrahepatic volumes, sinusoidal volume and extravascular volume accessible to albumin, were assessed by the multiple indicator dilution technique. Though 120-min hypoxia per se caused only a slight increase in the lactate dehydrogenase (LDH) release and no significant alterations in perfusion pressure and intrahepatic volumes, reoxygenation elicited hepatocellular injury assessed by the LDH level in the perfusate along with a substantial increase in perfusion pressure and an increase in extravascular volume. Nicardipine pretreatment attenuated the increase in LDH level, perfusion pressure and intrahepatic volumes after reoxygenation, but there were no difference in liver microcirculation during 120-min hypoxia. The data of the current study emphasized the crucial role of Ca2+ influx in hypoxic/reoxygenation hepatocellular injury and suggested that a direct vasodilating effect of nicardipine on the intrahepatic vasculature during hypoxia is unlikely as the mechanism for its cytoprotective effects.