Cellular and immunological basis of the host-parasite relationship during infection with Neospora caninum

Neospora caninum is an apicomplexan parasite that is closely related to Toxoplasma gondii, the causative agent of toxoplasmosis in humans and domestic animals. However, in contrast to T. gondii, N. caninum represents a major cause of abortion in cattle, pointing towards distinct differences in the biology of these two species. There are 3 distinct key features that represent potential targets for prevention of infection or intervention against disease caused by N. caninum. Firstly, tachyzoites are capable of infecting a large variety of host cells in vitro and in vivo. Secondly, the parasite exploits its ability to respond to alterations in living conditions by converting into another stage (tachyzoite-to-bradyzoite or vice versa). Thirdly, by analogy with T. gondii, this parasite has evolved mechanisms that modulate its host cells according to its own requirements, and these must, especially in the case of the bradyzoite stage, involve mechanisms that ensure long-term survival of not only the parasite but also of the host cell. In order to elucidate the molecular and cellular bases of these important features of N. caninum, cell culture-based approaches and laboratory animal models are being exploited. In this review, we will summarize the current achievements related to host cell and parasite cell biology, and will discuss potential applications for prevention of infection and/or disease by reviewing corresponding work performed in murine laboratory infection models and in cattle.

Alterations of exhaled nitric oxide in pre-term infants with chronic lung disease

Animal models suggest that reduced nitric oxide (NO) synthase activity results in lower values of exhaled NO (eNO) present at birth in those individuals who are going to develop chronic lung disease of infancy (CLDI). Online tidal eNO was measured in 39 unsedated pre-term infants with CLDI (mean gestational age (GA) 27.3 weeks) in comparison with 23 healthy pre-term (31.6 weeks) and 127 term infants (39.9 weeks) at 44 weeks post-conceptional age, thus after the main inflammatory response. NO output (NO output (V'(NO)) = eNO x flow) was calculated to account for tidal- flow-related changes. Sex, maternal atopic disease and environmental factors (smoking, caffeine) were controlled for. The mean eNO was not different (14.9 ppb in all groups) but V'(NO) was lower in CLDI compared with healthy term infants (0.52 versus 0.63 nL x s(-1)). Values for healthy pre-term infants were between these two groups (0.58 nL x s(-1)). Within all pre-term infants (n = 62), V'(NO) was reduced in infants with low GA, high clinical risk index for babies scores and longer duration of oxygen therapy but not associated with post-natal factors, such as ventilation or corticosteroid treatment. After accounting for flow, the lower nitric oxide output in premature infants with chronic lung disease of infancy is consistent with the hypothesis of nitric oxide metabolism being involved in chronic lung disease of infancy.

Mutations in Uroplakin IIIA are a rare cause of renal hypodysplasia in humans

BACKGROUND: Renal hypodysplasia, characterized by a decrease in nephron number, small overall kidney size, and maldeveloped renal tissue, is a leading cause of chronic renal failure in young children. Familial clustering and renal hypodysplasia phenotypes observed in transgenic animal models suggest a genetic contribution. Uroplakin IIIa (encoded by UPIIIA) is an integral membrane protein present in urothelial plaques, and the murine UPIIIa knockout is associated with urothelial anomalies and vesicoureteral reflux. De novo UPIIIA mutations recently were identified in 4 of 17 patients with severe bilateral renal adysplasia. METHODS: To evaluate the overall role of UPIIIA in human renal hypodysplasia pathogenesis, we performed UPIIIA mutation analysis in a cohort of 170 pediatric patients affected by severe unilateral or bilateral renal hypodysplasia. Eighty-one patients were affected by bilateral nonobstructive renal hypodysplasia; of these, 61 were without vesicoureteral reflux. Eighty-four patients presented with unilateral nonobstructive renal hypodysplasia, including 24 patients with unilateral multicystic dysplastic kidneys. Family history was positive in 11%. RESULTS: Mutation analysis showed 2 heterozygous mutations not observed in 200 race-matched control chromosomes. In only 1 family was distribution of the UPIIIA mutation consistent with a disease-causing effect. This de novo missense mutation (Gly202Asp) was identified in a patient with unilateral multicystic dysplastic kidneys. The second (intronically located) mutation appeared unlikely to be disease causing because it did not segregate with an obvious disease phenotype in the affected family. CONCLUSION: Our results indicate that de novo mutations in UPIIIA can be involved in defective early kidney development, but probably constitute only a rare cause of human renal hypodysplasia in a minor subset of individuals.

Seasonal changes in bone metabolism in sheep

There is a great need for animal models of osteoporosis and sheep are a suitable large animal that meets most requirements. Since it is known that bone mass in humans responds to seasonal changes, this study investigated natural bone metabolism in sheep in order to better define the sheep as a model for osteoporosis. Bone mineral density (BMD), trabecular structure, biochemical markers of bone formation and resorption and estrogen were analysed over a period of 18 months. The lowest BMDs, measured by peripheral quantitative computed tomography (pQCT), were observed during winter. Thereafter, a 5.1% increase in BMD was observed during spring and summer (P<0.05). Bone resorption markers showed a variable pattern, with higher values in spring compared to autumn (P<0.001). The physiological estrus phase during autumn was detected by serum estrogen levels. The findings show that it is necessary to take seasonal variations into account if sheep are used to establish an animal model for osteoporosis.

In utero haematopoietic stem cell transplantation. Experiences in mice, sheep and humans

Early prenatal diagnosis and in utero therapy of certain fetal diseases have the potential to reduce fetal morbidity and mortality. The intrauterine transplantation of stem cells provides in some instances a therapeutic option before definitive organ failure occurs. Clinical experiences show that certain diseases, such as immune deficiencies or inborn errors of metabolism, can be successfully treated using stem cells derived from bone marrow. However, a remaining problem is the low level of engraftment that can be achieved. Efforts are made in animal models to optimise the graft and study the recipient's microenvironment to increase long-term engraftment levels. Our experiments in mice show similar early homing of allogeneic and xenogeneic stem cells and reasonable early engraftment of allogeneic murine fetal liver cells (17.1% donor cells in peripheral blood 4 weeks after transplantation), whereas xenogeneic HSC are rapidly diminished due to missing self-renewal and low differentiation capacities in the host's microenvironment. Allogeneic murine fetal liver cells have very good long-term engraftment (49.9% donor cells in peripheral blood 16 weeks after transplantation). Compared to the rodents, the sheep model has the advantage of body size and gestation comparable to the human fetus. Here, ultrasound-guided injection techniques significantly decreased fetal loss rates. In contrast to the murine in utero model, the repopulation capacities of allogeneic ovine fetal liver cells are lower (0.112% donor cells in peripheral blood 3 weeks after transplantation). The effect of MHC on engraftment levels seems to be marginal, since no differences could be observed between autologous and allogeneic transplantation (0.117% donor cells vs 0.112% donor cells in peripheral blood 1 to 2 weeks after transplantation). Further research is needed to study optimal timing and graft composition as well as immunological aspects of in utero transplantation.

Functional properties of multiple isoforms of human divalent metal-ion transporter 1 (DMT1)

DMT1 (divalent metal-ion transporter 1) is a widely expressed metal-ion transporter that is vital for intestinal iron absorption and iron utilization by most cell types throughout the body, including erythroid precursors. Mutations in DMT1 cause severe microcytic anaemia in animal models. Four DMT1 isoforms that differ in their N- and C-termini arise from mRNA transcripts that vary both at their 5'-ends (starting in exon 1A or exon 1B) and at their 3'-ends giving rise to mRNAs containing (+) or lacking (-) the 3'-IRE (iron-responsive element) and resulting in altered C-terminal coding sequences. To determine whether these variations result in functional differences between isoforms, we explored the functional properties of each isoform using the voltage clamp and radiotracer assays in cRNA-injected Xenopus oocytes. 1A/IRE+-DMT1 mediated Fe2+-evoked currents that were saturable (K(0.5)(Fe) approximately 1-2 microM), temperature-dependent (Q10 approximately 2), H+-dependent (K(0.5)(H) approximately 1 muM) and voltage-dependent. 1A/IRE+-DMT1 exhibited the provisional substrate profile (ranked on currents) Cd2+, Co2+, Fe2+, Mn2+>Ni2+, V3+>>Pb2+. Zn2+ also evoked large currents; however, the zinc-evoked current was accounted for by H+ and Cl- conductances and was not associated with significant Zn2+ transport. 1B/IRE+-DMT1 exhibited the same substrate profile, Fe2+ affinity and dependence on the H+ electrochemical gradient. Each isoform mediated 55Fe2+ uptake and Fe2+-evoked currents at low extracellular pH. Whereas iron transport activity varied markedly between the four isoforms, the activity for each correlated with the density of anti-DMT1 immunostaining in the plasma membrane, and the turnover rate of the Fe2+ transport cycle did not differ between isoforms. Therefore all four isoforms of human DMT1 function as metal-ion transporters of equivalent efficiency. Our results reveal that the N- and C-terminal sequence variations among the DMT1 isoforms do not alter DMT1 functional properties. We therefore propose that these variations serve as tissue-specific signals or cues to direct DMT1 to the appropriate subcellular compartments (e.g. in erythroid cells) or the plasma membrane (e.g. in intestine).

Are radiogallium-labelled DOTA-conjugated somatostatin analogues superior to those labelled with other radiometals?

PURPOSE: Gallium-68 is a metallic positron emitter with a half-life of 68 min that is ideal for the in vivo use of small molecules, such as [68Ga-DOTA,Tyr3]octreotide, in the diagnostic imaging of somatostatin receptor-positive tumours. In preclinical studies it has shown a striking superiority over its 111In-labelled congener. The purpose of this study was to evaluate whether third-generation somatostatin-based, radiogallium-labelled peptides show the same superiority. METHODS: Peptides were synthesised on solid phase. The receptor affinity was determined by in vitro receptor autoradiography. The internalisation rate was studied in AR4-2J and hsst-HEK-transfected cell lines. The pharmacokinetics was studied in a rat xenograft tumour model, AR4-2J. RESULTS: All peptides showed high affinities on hsst2, with the highest affinity for the Ga(III)-complexed peptides. On hsst3 the situation was reversed, with a trend towards lower affinity of the Ga(III) peptides. A significantly increased internalisation rate was found in sst2-expressing cells for all 67Ga-labelled peptides. Internalisation into HEK-sst3 was usually faster for the 111In-labelled peptides. No internalisation was found into sst5. Biodistribution studies employing [67Ga-DOTA,1-Nal3]octreotide in comparison to [111In-DOTA,1-Nal3]octreotide and [67Ga-DOTA,Tyr3]octreotide showed a significantly higher and receptor-mediated uptake of the two 67Ga-labelled peptides in the tumour and somatostatin receptor-positive tissues. A patient study illustrated the potential advantage of a broad receptor subtype profile radiopeptide over a high-affinity sst2-selective radiopeptide. CONCLUSION: This study demonstrates that 67/68Ga-DOTA-octapeptides show distinctly better preclinical, pharmacological performances than the 111In-labelled peptides, especially on sst2-expressing cells and the corresponding animal models. They may be excellent candidates for further development for clinical studies.

ECG-triggered muscular counterpulsation for treatment of low cardiac output

BACKGROUND: Skeletal muscular counterpulsation (MCP) has been used as a new noninvasive technique for treatment of low cardiac output. The MCP method is based on ECG-triggered skeletal muscle stimulation. The purpose of the present study was to evaluate acute hemodynamic changes induced by MCP in the experimental animal. METHODS: Eight anaesthetized pigs (43+/-4 kg) were studied at rest and after IV â-blockade (10 mg propranolol) before and after MCP. Muscular counterpulsation was performed on both thighs using trains (75 ms duration) of multiple biphasic electrical impulses with a width of 1 ms and a frequency of 200 Hz at low (10 V) and high (30 V) amplitude. ECG-triggering was used to synchronize stimulation to a given time point. LV pressure-volume relations were determined using the conductance catheter. After baseline measurements, MCP was carried out for 10 minutes at low and high stimulation amplitude. The optimal time point for MCP was determined from LV pressure-volume loops using different stimulation time points during systole and diastole. Best results were observed during end-systole and, therefore, this time point was used for stimulation. RESULTS: Under control conditions, MCP was associated with a significant decrease in pulmonary vascular resistance (-18%), a decrease in systemic vascular resistance (-11%) and stroke work index (-4%), whereas cardiac index (+2%) and ejection fraction (+6%) increased slightly. Pressure-volume loops showed a leftward shift with a decrease in end-systolic volume. After â-blockade, cardiac function decreased (HR, MAP, EF, dP/dt max), but it improved with skeletal muscle stimulation (HR +10% and CI +17%, EF +5%). There was a significant decrease in pulmonary (-19%) and systemic vascular resistance (-29%). CONCLUSIONS: In the animal model, ECG-triggered skeletal muscular counterpulsation is associated with a significant improvement in cardiac function at baseline and after IV â-blockade. Thus, MCP represents a new, non-invasive technique which improves cardiac function by diastolic compression of the peripheral arteries and veins, with a decrease in systemic vascular resistance and increase in cardiac output.

Human adrenal corticocarcinoma NCI-H295R cells produce more androgens than NCI-H295A cells and differ in 3beta-hydroxysteroid dehydrogenase type 2 and 17,20 lyase activities

The human adrenal cortex produces mineralocorticoids, glucocorticoids, and androgens in a species-specific, hormonally regulated, zone-specific, and developmentally characteristic fashion. Most molecular studies of adrenal steroidogenesis use human adrenocortical NCI-H295A and NCI-H295R cells as a model because appropriate animal models do not exist. NCI-H295A and NCI-H295R cells originate from the same adrenocortical carcinoma which produced predominantly androgens but also smaller amounts of mineralocorticoids and glucocorticoids. Research data obtained from either NCI-H295A or NCI-H295R cells are generally compared, although for the same experiments no direct comparison between the two cell lines has been performed. Therefore, we compared the steroid profile and the expression pattern of important genes involved in steroidogenesis in both cell lines. We found that steroidogenesis differs profoundly. NCI-H295A cells produce more mineralocorticoids, whereas NCI-H295R cells produce more androgens. Expression of the 3beta-hydroxysteroid dehydrogenase (HSD3B2), cytochrome b5, and sulfonyltransferase genes is higher in NCI-H295A cells, whereas expression of the cytochrome P450c17 (CYP17), 21-hydroxylase (CYP21), and P450 oxidoreductase genes does not differ between the cell lines. We found lower 3beta-hydroxysteroid dehydrogenase type 2 but higher 17,20-lyase activity in NCI-H295R cells explaining the 'androgenic' steroid profile for these cells and resembling the zona reticularis of the human adrenal cortex. Both cell lines were found to express the ACTH receptor at low levels consistent with low stimulation by ACTH. By contrast, both cell lines were readily stimulated by 8Br-cAMP. The angiotensin type 1 receptor was highly expressed in NCI-H295R than NCI-H295A cells and angiotensin II stimulated steroidogenesis in NCI-H295R but not NCI-H295A cells. Our data suggest that comparative studies between NCI-H295A and NCI-H295R cells may help find important regulators of mineralocorticoid or androgen biosynthesis.

LIF promotes neurogenesis and maintains neural precursors in cell populations derived from spiral ganglion stem cells

BACKGROUND: Stem cells with the ability to form clonal floating colonies (spheres) were recently isolated from the neonatal murine spiral ganglion. To further examine the features of inner ear-derived neural stem cells and their derivatives, we investigated the effects of leukemia inhibitory factor (LIF), a neurokine that has been shown to promote self-renewal of other neural stem cells and to affect neural and glial cell differentiation. RESULTS: LIF-treatment led to a dose-dependent increase of the number of neurons and glial cells in cultures of sphere-derived cells. Based on the detection of developmental and progenitor cell markers that are maintained in LIF-treated cultures and the increase of cycling nestin-positive progenitors, we propose that LIF maintains a pool of neural progenitor cells. We further provide evidence that LIF increases the number of nestin-positive progenitor cells directly in a cell cycle-independent fashion, which we interpret as an acceleration of neurogenesis in sphere-derived progenitors. This effect is further enhanced by an anti-apoptotic action of LIF. Finally, LIF and the neurotrophins BDNF and NT3 additively promote survival of stem cell-derived neurons. CONCLUSION: Our results implicate LIF as a powerful tool to control neural differentiation and maintenance of stem cell-derived murine spiral ganglion neuron precursors. This finding could be relevant in cell replacement studies with animal models featuring spiral ganglion neuron degeneration. The additive effect of the combination of LIF and BDNF/NT3 on stem cell-derived neuronal survival is similar to their effect on primary spiral ganglion neurons, which puts forward spiral ganglion-derived neurospheres as an in vitro model system to study aspects of auditory neuron development.

An infant mouse model of brain damage in pneumococcal meningitis

Bacterial meningitis due to Streptococcus pneumoniae is associated with an significant mortality rate and persisting neurologic sequelae including sensory-motor deficits, seizures, and impairments of learning and memory. The histomorphological correlate of these sequelae is a pattern of brain damage characterized by necrotic tissue damage in the cerebral cortex and apoptosis of neurons in the hippocampal dentate gyrus. Different animal models of pneumococcal meningitis have been developed to study the pathogenesis of the disease. To date, the infant rat model is unique in mimicking both forms of brain damage documented in the human disease. In the present study, we established an infant mouse model of pneumococcal meningitis. Eleven-days-old C57BL/6 (n = 299), CD1 (n = 42) and BALB/c (n = 14) mice were infected by intracisternal injection of live Streptococcus pneumoniae. Sixteen hours after infection, all mice developed meningitis as documented by positive bacterial cultures of the cerebrospinal fluid. Sixty percent of infected C57BL/6 mice survived more than 40 h after infection (50% of CD1, 0% of BALB/c). Histological evaluations of brain sections revealed apoptosis in the dentate gyrus of the hippocampus in 27% of infected C57BL/6 and in 5% of infected CD1 mice. Apoptosis was confirmed by immunoassaying for active caspase-3 and by TUNEL staining. Other forms of brain damage were found exclusively in C57BL/6, i.e. caspase-3 independent (pyknotic) cell death in the dentate gyrus in 2% and cortical damage in 11% of infected mice. This model may prove useful for studies on the pathogenesis of brain injury in childhood bacterial meningitis.

Mechanisms of brain injury in bacterial meningitis: workshop summary

Morbidity and mortality associated with bacterial meningitis remain high, although antibiotic therapy has improved during recent decades. The major intracranial complications of bacterial meningitis are cerebrovascular arterial and venous involvement, brain edema, and hydrocephalus with a subsequent increase of intracranial pressure. Experiments in animal models and cell culture systems have focused on the pathogenesis and pathophysiology of bacterial meningitis in an attempt to identify the bacterial and/or host factors responsible for brain injury during the course of infection. An international workshop entitled "Bacterial Meningitis: Mechanisms of Brain Injury" was organized by the Department of Neurology at the University of Munich and was held in Eibsee, Germany, in June 1993. This conference provided a forum for the exchange of current information on bacterial meningitis, including data on the clinical spectrum of complications, the associated morphological alterations, the role of soluble inflammatory mediators (in particular cytokines) and of leukocyte-endothelial cell interactions in tissue injury, and the molecular mechanisms of neuronal injury, with potential mediators such as reactive oxygen species, reactive nitrogen species, and excitatory amino acids. It is hoped that a better understanding of the pathophysiological events that take place during bacterial meningitis will lead to the development of new therapeutic regimens.

Induction of Bim and Bid gene expression during accelerated apoptosis in severe sepsis

ABSTRACT: INTRODUCTION: In transgenic animal models of sepsis, members of the Bcl-2-family of proteins regulate lymphocyte apoptosis and survival of sepsis. This study investigates the gene regulation of pro- and anti-apoptotic members of the Bcl-2-family of proteins in patients with early stage severe sepsis. METHODS: In this prospective case-control study patients were recruited from three intensive care units in a university hospital. Sixteen patients were enrolled as soon as they fulfilled the criteria of severe sepsis. Ten critically ill but non-septic patients and eleven healthy volunteers served as controls. Blood samples were immediately obtained at inclusion. To confirm the presence of accelerated apoptosis in the patient groups, caspase-3 activation and phosphatidylserine (PS) externalization in CD4+, CD8+ and CD19+ lymphocyte subsets were assessed by flow cytometry. Specific mRNA's of Bcl-2 family members were quantified from whole blood by real-time polymerase chain reaction. To test for statistical significance, Kruskal-Wallis testing with Dunn's multiple comparison test for post hoc testing was performed. RESULTS: In all lymphocyte populations caspase-3 (p<0.05) was activated, which was reflected in an increased PS externalization (p<0.05). Accordingly, lymphocyte counts were decreased in early severe sepsis. In CD4+ T-cells (p<005) and in B-cells (p<0.001) the Bcl-2 protein was decreased in severe sepsis. Gene expression of the BH3-only Bim was massively upregulated as compared to critically ill patients (p<0.001) and 51.6 fold as compared to healthy controls (p<0.05). Bid was increased 12.9 fold compared to critically ill (p<0.001). In the group of the mitochondrial apoptosis-inducers, Bak was upregulated 5.6 fold, while the expression of Bax showed no significant variations. By contrast, the pro-survival members Bcl-2 and Bcl-xl were both downregulated in severe sepsis (p<0.001, p<0.05). CONCLUSIONS: In early severe sepsis a gene expression pattern with induction of the pro-apoptotic Bcl-2 family members Bim, Bid and Bak and a downregulation of the anti-apoptotic Bcl-2 and Bcl-xl was observed in peripheral blood. This constellation may affect cellular susceptibility to apoptosis and complex immune dysfunction in sepsis.

High level of extracellular potassium and its correlates after severe head injury: relationship to high intracranial pressure

OBJECT: Disturbed ionic and neurotransmitter homeostasis are now recognized as probably the most important mechanisms contributing to the development of secondary brain swelling after traumatic brain injury (TBI). Evidence obtained in animal models indicates that posttraumatic neuronal excitation by excitatory amino acids leads to an increase in extracellular potassium, probably due to ion channel activation. The purpose of this study was therefore to measure dialysate potassium in severely head injured patients and to correlate these results with measurements of intracranial pressure (ICP), patient outcome, and levels of dialysate glutamate and lactate, and cerebral blood flow (CBF) to determine the role of ischemia in this posttraumatic ion dysfunction. METHODS: Eighty-five patients with severe TBI (Glasgow Coma Scale Score < 8) were treated according to an intensive ICP management-focused protocol. All patients underwent intracerebral microdialyis. Dialysate potassium levels were analyzed using flame photometry, and dialysate glutamate and dialysate lactate levels were measured using high-performance liquid chromatography and an enzyme-linked amperometric method in 72 and 84 patients, respectively. Cerebral blood flow studies (stable xenon computerized tomography scanning) were performed in 59 patients. In approximately 20% of the patients, dialysate potassium values were increased (dialysate potassium > 1.8 mM) for 3 hours or more. A mean amount of dialysate potassium greater than 2 mM throughout the entire monitoring period was associated with ICP above 30 mm Hg and fatal outcome, as were progressively rising levels of dialysate potassium. The presence of dialysate potassium correlated positively with dialysate glutamate (p < 0.0001) and lactate (p < 0.0001) levels. Dialysate potassium was significantly inversely correlated with reduced CBF (p = 0.019). CONCLUSIONS: Dialysate potassium was increased after TBI in 20% of measurements. High levels of dialysate potassium were associated with increased ICP and poor outcome. The simultaneous increase in dialysate potassium, together with dialysate glutamate and lactate, supports the concept that glutamate induces ionic flux and consequently increases ICP, which the authors speculate may be due to astrocytic swelling. Reduced CBF was also significantly correlated with increased levels of dialysate potassium. This may be due to either cell swelling or altered vasoreactivity in cerebral blood vessels caused by higher levels of potassium after trauma. Additional studies in which potassium-sensitive microelectrodes are used are needed to validate these ionic events more clearly.

High extracellular potassium and its correlates after severe head injury: relationship to high intracranial pressure

Disturbed ionic and neurotransmitter homeostasis are now recognized to be probably the most important mechanisms contributing to the development of secondary brain swelling after traumatic brian injury (TBI). Evidence obtained from animal models indicates that posttraumatic neuronal excitation via excitatory amino acids leads to an increase in extracellular potassium, probably due to ion channel activation. The purpose of this study was therefore to measure dialysate potassium in severely head injured patients and to correlate these results with intracranial pressure (ICP), outcome, and also with the levels of dialysate glutamate, lactate, and cerebral blood flow (CBF) so as to determine the role of ischemia in this posttraumatic ionic dysfunction. Eighty-five patients with severe TBI (Glasgow Coma Scale score < 8) were treated according to an intensive ICP management-focused protocol. All patients underwent intracerebral microdialyis. Dialysate potassium levels were analyzed by flame photometry, as were dialysate glutamate and dialysate lactate levels, which were measured using high-performance liquid chromatography and an enzyme-linked amperometric method in 72 and 84 patients respectively. Cerebral blood flow studies (stable Xenon--computerized tomography scanning) were performed in 59 patients. In approximately 20% of the patients, potassium values were increased (dialysate potassium > 1.8 mmol). Mean dialysate potassium (> 2 mmol) was associated with ICP above 30 mm Hg and fatal outcome. Dialysate potassium correlated positively with dialysate glutamate (p < 0.0001) and lactate levels (p < 0.0001). Dialysate potassium was significantly inversely correlated with reduced CBF (p = 0.019). Dialysate potassium was increased after TBI in 20% of measurements. High levels of dialysate potassium were associated with increased ICP and poor outcome. The simultaneous increase of potassium, together with dialysate glutamate and lactate, supports the hypothesis that glutamate induces ionic flux and consequently increases ICP due to astrocytic swelling. Reduced CBF was also significantly correlated with increased levels of dialysate potassium. This may be due to either cell swelling or altered potassium reactivity in cerebral blood vessels after trauma.