Implication of the polyamines in the neurotoxic effects ofN-methyl-D-aspartate

N-Methyl-D-aspartate (NMDA) receptor activation selectively releases the polyamines spermine and spermidine from the rat striatum in vivo. The intrastriatal injection of spermine or spermidine is neurotoxic, but this toxicity is not blocked by MK-801 and unlikely to be mediated via the NMDA receptor. The neurotoxic effects of intrastriatally injected NMDA can, however, be reduced by polyamine synthesis inhibition with difluoromethylornithine. Alterations in polyamine metabolism in the ischaemic brain, although perhaps induced by NMDA receptor activation, may contribute to ischaemic cell loss via NMDA-independent mechanisms, possibly related to the diverse effects of polyamines on calcium homoeostasis and channel function.

Sequential measurements of troponin Ic values in brain-dead patients considered as potential heart donors

It was suggested that a single value of normal or increased plasma cardiac troponin T or I (cTnT or cTnI) concentration could contribute to estimate donor myocardial damage and function in brain-dead patients. In patients with acute coronary syndromes, an initial normal value of troponin must be confirmed several hours later but no such recommendations exist for brain-dead patients. We investigated the relationship between two sequential (6 h interval) measurements of plasma cTnI concentrations in brain-dead patients considered as potential heart donors. The first and the second TnIc values were correlated with an adjusted r2 value of 0.92 (p<0.001). Our results suggest therefore that it is not necessary to repeat the measurements, when the value of plasma cTnI concentration is taken into consideration in the algorithm for cardiac harvesting.

SSR180711, a novel selective alpha7 nicotinic receptor partial agonist: (1) binding and functional profile

In this paper, we report on the pharmacological and functional profile of SSR180711 (1,4-Diazabicyclo[3.2.2]nonane-4-carboxylic acid, 4-bromophenyl ester), a new selective alpha7 acetylcholine nicotinic receptor (n-AChRs) partial agonist. SSR180711 displays high affinity for rat and human alpha7 n-AChRs (K(i) of 22+/-4 and 14+/-1 nM, respectively). Ex vivo (3)[H]alpha-bungarotoxin binding experiments demonstrate that SSR180711 rapidly penetrates into the brain (ID(50)=8 mg/kg p.o.). In functional studies performed with human alpha7 n-AChRs expressed in Xenopus oocytes or GH4C1 cells, the compound shows partial agonist effects (intrinsic activity=51 and 36%, EC(50)=4.4 and 0.9 microM, respectively). In rat cultured hippocampal neurons, SSR180711 induced large GABA-mediated inhibitory postsynaptic currents and small alpha-bungarotoxin sensitive currents through the activation of presynaptic and somato-dendritic alpha7 n-AChRs, respectively. In mouse hippocampal slices, the compound increased the amplitude of both glutamatergic (EPSCs) and GABAergic (IPSCs) postsynaptic currents evoked in CA1 pyramidal cells. In rat and mouse hippocampal slices, a concentration of 0.3 muM of SSR180711 increased long-term potentiation (LTP) in the CA1 field. Null mutation of the alpha7 n-AChR gene totally abolished SSR180711-induced modulation of EPSCs, IPSCs and LTP in mice. Intravenous administration of SSR180711 strongly increased the firing rate of single ventral pallidum neurons, extracellularly recorded in anesthetized rats. In microdialysis experiments, administration of the compound (3-10 mg/kg i.p.) dose-dependently increased extracellular acetylcholine (ACh) levels in the hippocampus and prefrontal cortex of freely moving rats. Together, these results demonstrate that SSR180711 is a selective and partial agonist at human, rat and mouse alpha7 n-AChRs, increasing glutamatergic neurotransmission, ACh release and LTP in the hippocampus.

Analyse des critères qui participent à la décision de prélèvement cardiaque chez les patients en état de mort encéphalique

OBJECTIVES

The number of cardiac transplantation procedures does not increase because of the lack of donor hearts despite an increase in the number of brain-dead organ donors. The criteria used to select a donor heart are not formally standardized. The aim of the present study was to analyze the criteria that contribute to the selection of a donor heart.

TYPE OF STUDY

Descriptive, retrospective study.

PATIENTS AND METHOD

Clinical parameters, the initial causes that lead to brain death, maximum doses of catecholamines, several biochemical markers of myocardial ischaemia/necrosis as well as several echocardiography criteria were extracted from a prospectively collected database. Univariate and multivariate (logistic regression) analyses were performed with the "harvested heart" as dependent variable and the above-cited independent variables.

RESULTS

One hundred and eighty consecutive brain-dead patients admitted from 1st October 1998 to 31st December 2000 out of which 112 gave at least one organ were analyzed. Among these 112 patients, 59 (39 males and 20 females) were pre-selected as potential heart donors. Only 44 hearts were harvested. Logistic regression analysis showed that harvesting of the heart was more probable if the donor were a male, had no left ventricle systolic wall motion abnormalities, had low doses of norepinephrine and low serum troponin Ic concentrations.

CONCLUSION

After an initial phase of selection, the final decision to harvest a heart is based on several criteria. These results should be an incentive to conceive a score that could allow a more formal decision process for heart harvesting.

SSR591813, a novel selective and partial alpha4beta2 nicotinic receptor agonist with potential as an aid to smoking cessation

(5aS,8S,10aR)-5a,6,9,10-Tetrahydro,7H,11H-8,10a-methanopyrido[2',3':5,6]pyrano[2,3-d]azepine (SSR591813) is a novel compound that binds with high affinity to the rat and human alpha4beta2 nicotinic acetylcholine receptor (nAChR) subtypes (Ki = 107 and 36 nM, respectively) and displays selectivity for the alpha4beta2 nAChR (Ki, human alpha3beta4 > 1000, alpha3beta2 = 116; alpha1beta1deltagamma > 6000 nM and rat alpha7 > 6000 nM). Electrophysiological experiments indicate that SSR591813 is a partial agonist at the human alpha4beta2 nAChR subtype (EC50 = 1.3 micro M, IA =19% compared with the full agonist 1,1-dimethyl-4-phenyl-piperazinium). In vivo findings from microdialysis and drug discrimination studies confirm the partial intrinsic activity of SSR591813. The drug increases dopamine release in the nucleus accumbens shell (30 mg/kg i.p.) and generalizes to nicotine or amphetamine (10-20 mg/kg i.p.) in rats, with an efficacy approximately 2-fold lower than that of nicotine. Pretreatment with SSR591813 (10 mg/kg i.p.) reduces the dopamine-releasing and discriminative effects of nicotine. SSR591813 shows activity in animal models of nicotine dependence at doses devoid of unwanted side effects typically observed with nicotine (hypothermia and cardiovascular effects). The compound (10 mg/kg i.p.) also prevents withdrawal signs precipitated by mecamylamine in nicotine-dependent rats and partially blocks the discriminative cue of an acute precipitated withdrawal. SSR591813 (20 mg/kg i.p.) reduces i.v. nicotine self-administration and antagonizes nicotine-induced behavioral sensitization in rats. The present results confirm important role for alpha4beta2 nAChRs in mediating nicotine dependence and suggest that SSR591813, a partial agonist at this particular nAChR subtype, may have therapeutic potential in the clinical management of smoking cessation.

SR141716, a central cannabinoid (CB(1)) receptor antagonist, blocks the motivational and dopamine-releasing effects of nicotine in rats

The central CB(1) cannabinoid receptor has recently been implicated in brain reward function. In the present study we evaluated first the effects of the selective CB(1) receptor antagonist, SR141716, on the motivational effects of nicotine in the rat. Administration of SR141716 (0.3 and 1 mg/kg) decreased nicotine self-administration (0.03 mg/kg/injection). SR141716 (0.3-3 mg/kg) neither substituted for nicotine nor antagonized the nicotine cue in a nicotine discrimination procedure, but dose-dependently (0.01-1 mg/kg) antagonized the substitution of nicotine for D-amphetamine, in rats trained to discriminate D-amphetamine. Secondly, using brain microdialysis, SR141716 (1-3 mg/kg) blocked nicotine-induced dopamine release in the shell of the nucleus accumbens (NAc) and the bed nucleus of the stria terminalis. To investigate whether SR141716 would block the dopamine-releasing effects of another drug of abuse, we extended the neurochemical study to the effect of ethanol, consumption of which in rodents is reduced by SR141716. Dopamine release induced by ethanol in the NAc was also reduced by SR141716 (3 mg/kg). These results suggest that activation of the endogenous cannabinoid system may participate in the motivational and dopamine-releasing effects of nicotine and ethanol. Thus, SR141716 may be effective in reduction of alcohol consumption, as previously suggested, and as an aid for smoking cessation.

Evaluation of donor cardiac function for heart transplantation: experience of a French academic hospital

OBJECTIVES

The diagnostic and therapeutic approaches for evaluation and management of cardiac function in brain-dead patients vary from country to country. The aim of the present study was to describe the results of the evaluation of brain-dead patients as potential cardiac donors in a French teaching hospital that manages the largest number of brain-dead patients in France.

METHODS

Demographic parameters, the causes of brain death, clinical evolution, hemodynamic parameters, doses of inotropic and/or vasopressive drugs, the results of echocardiographic examination, and several biochemical markers of myocardial cell injury were retrospectively collected.

RESULTS

Seventy-one consecutive brain-dead patients admitted to the intensive care unit of the Academic Hospital of Nancy from October 1st, 1998 to September 30, 1999 were analyzed. Twenty-nine patients were considered as potential heart donors: 22 males and 7 females aged 33 +/- 3 years (Mean + SEM). The cause of brain death was head trauma in 17 cases (59%), cerebrovascular disease in 10 cases (34%), and cerebral anoxia related to cardiac arrest in 2 cases (7%). Eighteen hearts (18/29 or 66%) were harvested and transplanted with a favorable outcome at one month in 17 cases. In 11 cases, the heart was not harvested, nine (9/29 or 31%) because of myocardial dysfunction upon subsequent echocardiographic examination and 2 because of the lack of matched recipients.

CONCLUSION

Comparison of these results with those of other groups suggests that hormonal substitution with insulin and triiodothyronine in the presence of myocardial dysfunction could be of potential interest to correct myocardial dysfunction and increase the number of donor hearts.

Assessment of deep vein thrombosis prophylaxis in surgical patients: a study conducted at Nancy University Hospital, France

OBJECTIVE

This retrospective evaluation aimed to assess the adequacy of prophylaxis against thromboembolism prescribed to surgical patients at the authors' institution, and to compare it with generally accepted published guidelines. Aspects considered were indications for prophylaxis, regimens used and monitoring.

METHODS

Eleven units (nine surgical and two surgical intensive care) took part in the survey on a voluntary basis. The clinical audit system used involved developing a set of criteria based on existing guidelines, comparing observed practice with those recommendations, analysing the factors underlying any deviation and developing corrective measures.

RESULTS

When the medical records of 117 patients hospitalized in October 1995 were examined, prophylaxis against deep vein thrombosis was documented in 86 (low molecular weight heparin in 85, dextran in one). No associated physical preventative measures were recorded. Indications and dosage were appropriately handled in 90.7% and 75.2% of patients, respectively. Ninety-five cases were outside the reference criteria: 74 for excluded surgical indications, 13 which involved laparoscopy, and eight in which spinal or epidural anaesthesia was administered. Platelet count was performed in 73.8% of cases before prophylactic treatment, and in 23.10% during its course. Anti-Xa activity was measured in 0.4% of cases. Analysis of causes showed that guidelines were not complied with either because of lack of organization, or because of disagreement with them.

DISCUSSION

In this study, indications for prophylaxis were well established and heparin dosages used were not fundamentally flawed. The weak point in practice was a failure to carry out platelet counts, particularly during the course of treatment. Appropriate corrective action consists of disseminating guidelines and relevant information, and using a preoperative checklist to assess thromboembolic risk.

CONCLUSION

Physicians agree that opportunities to improve preventative practices exist, and that the quality improvement programme should be pursued.

Variations in plasma sodium concentration in post-operative patients depend on an electrolyte-free water balance, part of a tonicity balance

BACKGROUND

There is an inverse relationship between changes in the concentration of sodium in plasma (PNa) and intracellular fluid (ICF) volume. Intakes and losses of sodium (Na), potassium (K) and water can be divided into two volumes: isotonic and electrolyte-free water (EFW). Calculations of these volumes assess a tonicity balance, a tonicity imbalance results in a change of PNa: when EFW is added to body fluids, PNa decreases. Moreover, the concept of EFW permits a good understanding of the renal contribution to the defence of body tonicity.

PURPOSE

To illustrate that the measurement of a tonicity balance provides the best estimate of changes in PNa in an ICU setting.

METHODS

Twenty-two patients were admitted to the Post-Operative Intensive Care Unit. We investigated how well changes in EFW balance correlated with PNa variations and what is the best formula to calculate EFW in this setting.

RESULTS

PNa changes depend on EFW balance; there is no significant relationship with other classical factors such as urinary osmolality or Na-free water.

CONCLUSION

The utility of a tonicity balance is demonstrated. A formula is derived facilitating at the bedside the prediction of changes in PNa following fluid therapy: PNa2 = [(PNa1.TBW) + balance (Na + K)]/[TBW + balance H2O]. PNa changes can be understood and/or modified exclusively by a careful measurement of intakes and losses of Na, K and water.

[Complications of vascular surgery]

Vascular surgery, which in certain life-threatening situations is the only possible therapeutic option, has progressed considerably since its beginning in the 1950s. Because of the constant progression of vascular diseases, this surgery will present, in the forthcoming years, a major public health problem. Because of advances in medico-surgical management, evermore elderly and frail patients can be treated. Perioperative mortality is constantly decreasing, but much progress remains to be accomplished to prevent, avoid or treat, postoperative complications. They are common and serious in these typical patients with cardiovascular diseases (men over 50 years of age, heavy smokers, atheromatous ...). The AA divide these complications into 3 main groups depending on the surgical procedure: abdominal aortic surgery, carotid surgery and arterial and venous surgery of the lower limbs. There is much data on abdominal aortic surgery because these long and complex procedures produce repercussions often involving many systems. The postoperative complications are treated according to the system they involve: cardiovascular, the most serious, respiratory, the commonest, alimentary, neurological, renal, others, as well as combined systems. The AA do not deal with the specific problems associated with cardiac and cardio-thoracic surgery. The AA discuss the different epidemiological findings of the large surgical series published in the 1970s and 1980s. The more recent literature analyses the relationship between preoperative risk factors (atheroma, COAD, hypertension ...), peroperative problems (surgical difficulties, emergencies, massive transfusions, others) and the corresponding postoperative morbidity. Thus a few general outlines of the physiopathology of these different complications emerge. In the light of these notions the few proposed methods will be evaluated in order to improve the preoperative condition of the vascular patient. The AA also review the relevance of the preoperative investigation in patients for vascular surgery. All these measures aim at reducing the incidence and severity of perioperative morbidity.

Anti-anaphylactic activity of the novel selective histamine H1 receptor antagonist mizolastine in the rodent

The anti-anaphylactic/anti-histamine activity of mizolastine (CAS 108612-45-9, SL 85.0324), a novel histamine H1 receptor antagonist devoid of sedative properties, has been evaluated in the rat, mouse and guinea pig. Mizolastine inhibited the passive cutaneous anaphylactic reduction caused by ovalbumin challenge in the rat (ED50 = 0.7 mg/kg i.v., 1.6 mg/kg p.o.) and effectively protected rats from the lethal shock induced by compound 48/80 (ED50 = 0.07 mg/kg p.o.). Mizolastine protected actively sensitized guinea pigs from anaphylactic mortality, bronchospasm and respiratory difficulties (increase in pulmonary resistance) preceding this event and from morphological modifications at doses from 0.05 mg/kg i.v. The pharmacological activity of mizolastine is linked to a selective blockade of histamine H1 receptors as indicated by the ability of this compound to antagonize rat paw edema induced by the subplantar injection of histamine (ED50 = 0.5 mg/kg p.o.) but not that induced by the injection of serotonin or bradykinin. Mizolastine also antagonized the increase in cutaneous capillary permeability caused by the intradermal injection of histamine (-80% at 0.3 mg/kg p.o.) and compound 48/80 (ED50 = 1.1 mg/kg p.o.) but not that induced by serotonin in the rat. In the guinea pig, mizolastine antagonized i.v. histamine-induced bronchoconstriction (ED50 = 0.03 mg/kg p.o.) and histamine-induced vascular permeability and edema in trachea and bronchi (ED50 < or = 0.05 mg/kg i.v.). Moreover, at higher doses, mizolastine antagonized the bronchospasm caused by systemic injection of platelet-activating factor (PAF) and leukotriene D4 (LTD4) (ED50's = 0.30 and 3.0 mg/kg p.o., respectively). However, mizolastine only weakly antagonized bronchospasm induced by aerosolized PAF (-67% at 50 mg/kg p.o.), failed to antagonize (up to 3 mg/kg i.v.) PAF-induced microvascular permeability of the tracheal mucosa in the guinea pig and was a weak inhibitor of PAF-induced platelet aggregation in the rabbit (IC50 = 74 mumol/l). In addition to antagonizing histamine H1 receptors, mizolastine also inhibits the release of histamine during allergic reactions in tissues. Thus, mizolastine antagonizes the antigen-induced in vivo release of histamine from mast cells in bronchoalveolar lavages of actively sensitized guinea pigs (minimal effective dose 0.3 mg/kg p.o.) and the release of histamine from mast cells in the peritoneal fluid of passively sensitized rats (ED50 = 0.9 mg/kg i.v.). In these various models, mizolastine was more potent than loratadine and terfenadine but less potent than ketotifen. The apparent half-life for the pharmacological actions of mizolastine ranged from 6 to 8 h.(ABSTRACT TRUNCATED AT 400 WORDS)

Release of spermidine from the rat cortex following permanent middle cerebral artery occlusion

We have studied the effects of middle cerebral artery (MCA) occlusion in rats on polyamine efflux in the parietal cortex using the microdialysis technique. Dialysis probe implantation itself provoked a delayed, prolonged and vigorous release of spermidine and putrescine. Spermidine release returned to stable baseline levels within 48 hours. Putrescine release also returned to lower levels within this time period but putrescine levels in the dialysate fluctuated dramatically in individual animals. Because of the underlying effects of the dialysis probe (likely a reflection of traumatic cerebral damage and stimulation of polyamine metabolism and release within the immediate vicinity of the dialysis probe), MCA occlusion was performed 48 hours after probe implantation. MCA occlusion persistently (5/5 animals) resulted in a significant increase in cortical spermidine efflux, although the onset, magnitude and duration of this increased release was variable. Putrescine efflux was significantly increased in 2/5 animals with MCA occlusion but the increase in release was similar to the spontaneous fluctuations observed in control animals. Spermine was not detectable in cortical dialysates of control or MCA occluded groups. Spermidine, but not spermine or putrescine is consistently released from the parietal cortex following permanent focal ischaemia and may contribute to ischaemic neuropathology either through its effects at the N-methyl-D-aspartate (NMDA) receptor or via direct, and as yet uncharacterised, neurotoxic effects.

Synergism between the NMDA receptor antagonistic effects of ifenprodil and the glycine antagonist, 7-chlorokynurenate, in vivo

Ifenprodil (30 mg/kg i.p.) when administered alone did not antagonise the stimulatory effects of intrastriatally administered N-methyl-D-aspartate (NMDA: 500 microM, via a dialysis fibre) on spermine or spermidine release. The effects of NMDA were antagonised by the intrastriatal co-infusion of the glycine site antagonist, 7-chlorokynurenate (100 microM). Lower concentrations of 7-chlorokynurenate (3 microM) were without effect on the NMDA response. In the presence of a subthreshold concentration of striatally infused 7-chlorokynurenate (3 microM), systemically administered ifenprodil (30 mg/kg i.p.) blocked the effects of NMDA on polyamine release and also potentiated the inhibitory effects of 30 microM 7-chlorokynurenate. These results demonstrate that synergism between glycine antagonists and polyamine antagonists, as previously observed in vitro, is also observed in vivo.

Characterization of the calcium and chloride [3H]glutamate binding site in crude synaptic membranes from human brain tissue

1. The specific binding properties of [3H]glutamate to crude synaptic membranes (CSM) from postmortem human brain were studied. 2. Equilibrium binding analysis of [3H]glutamate binding to CSM from human brain cortex revealed a KD = 110 +/- 12 nM and a Bmax = 27 +/- 4 pmol/mg protein). 3. Calcium increased the number of binding sites, Bmax = 44 +/- 6 pmol/mg protein, without a significant change in the affinity constant, KD = 95 +/- 10 nM. 4. The dissociation constant of the [3H]glutamate bound to human CSM was 4.0 +/- 0.4 min-1 (n = 3). 5. The relative potencies of glutamate analogs and 2-amino-4-phosphonobutyric acid (APB) to compete for the glutamate binding sites, in human CSM, were glutamate > quisqualate = ibotenic acid > APB >> alpha-amino-3-hydroxy-5-methyl-4-isoxozolepropionate acid. 6. The glutamate specific binding in CSM from postmortem human brain was particularly rich in the gyrus hippocampus, nucleus accumbens, thalamus and frontal cortex. 7. This glutamate binding protein is related, probably, to a presynaptic neurosecretory pathway.

Ouabain releases striatal polyamines in vivo independently of N-methyl-D-aspartate receptor activation

Intrastriatally infused ouabain (200 or 1,000 microM) markedly increased the extracellular levels of striatal spermidine and spermine in dialysis experiments in halothane-anesthetized rats. The effects of ouabain (1 mM) on spermidine release were rapid and unaffected by local infusion of the competitive N-methyl-D-aspartate (NMDA) antagonist 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP; 100 microM) or by systemically administered MK-801 (0.3 mg/kg i.p.), both of which treatments markedly inhibit the effects of intrastriatally administered NMDA. The peak effects of ouabain (1 mM) on spermine release were delayed with respect to those on spermidine release, or to the effects of NMDA, and were also insensitive to locally administered CPP (100 microM). However, systemically administered MK-801 (0.3 mg/kg i.p., 30 min before the striatal infusion of drugs), which totally inhibits the effects of NMDA, or CPP (10 mg/kg i.p.; 30 min before the striatal infusion of drugs) partially inhibited the effects of ouabain on spermine release, suggesting partial mediation of the delayed effects of ouabain on spermine release by indirect NMDA-receptor activation. Despite partial sensitivity of ouabain-induced spermine release to systemically administered NMDA antagonists, both spermidine and spermine can be released in vivo by sodium-pump inhibition, independently of NMDA-receptor activation.

Ornithine decarboxylase inhibition or NMDA receptor antagonism reduce cortical polyamine efflux associated with dialysis probe implantation

Dialysis probe implantation in the rat parietal cortex results in delayed, prolonged and biphasic increases in the efflux of putrescine and spermidine with primary and secondary efflux peaks 6-8 h and 20-24 h after implantation. Putrescine and spermidine efflux remain elevated for at least 30 h after implantation. The primary efflux peak is attenuated by the continual infusion via the dialysis probe of either the ornithine decarboxylase inhibitor difluoromethylornithine or by the NMDA antagonist 2-APV. The secondary peak is resistant to either of these treatments. These changes in polyamine outflow are likely related to the traumatic brain damage associated with dialysis probe implantation which may be a useful model to study the effects of local brain trauma.

[Rhabdomyolysis after ORL surgery in prolonged lateral position]

Two cases are reported of upper limb rhabdomyolysis occurring after prolonged ENT cancer surgery, the patient being part of the time in the right lateral position, with the left forearm outstretched. Surgery consisted of a vertical hemilaryngectomy with immediate parascapular free graft reconstruction in a 48-year-old man (10 h of surgery, with 6 h in a lateral position) and the surgical removal of a neoplasm involving the mouth floor and larynx in a 62-year-old man including parascapsular free graft reconstruction (10 h of surgery, with 7 h in a lateral position). In the early postoperative period, the patients complained of severe pain in the left forearm. There was a tense painful swelling of the forearm, combined with an increase in creatinine kinase plasma concentration, and myoglobinaemia. The mechanism involved was most likely a compression of the forearm muscles, together with prolonged surgery and the patient position. The part played by the state of the patients is discussed. Diagnosis must be made as soon as possible, as the only efficient treatment consists of an early fasciotomy together with the administration of alkali to avoid renal failure.

Selective release of spermine and spermidine from the rat striatum by N-methyl-D-aspartate receptor activation in vivo

The intrastriatal infusion of N-methyl-D-aspartate (NMDA; 250-1,000 microM) via a dialysis cannula in anesthetized rats resulted in a marked and rapid increase in the concentrations of spermine and spermidine recovered in the dialysate. Extracellular concentrations of NMDA-released spermine and spermidine were calculated to be in the low micromolar range. Putrescine levels were not significantly affected by NMDA. The effects of NMDA (500 microM) were blocked by the previous systemic injection of MK-801 (3 mg/kg, i.p.) but were insensitive to the intrastriatal infusion of tetrodotoxin (1 microM). Intrastriatally infused kainate or quisqualate (1,000 microM) did not increase polyamine levels in the dialysate. Spermine and spermidine dialysate levels were also significantly increased by the infusion of high concentrations of K+ (greater than 100 mM), although the effects of K+ were considerably less marked than those of NMDA. Striatal polyamines are released into the extracellular space specifically by NMDA receptor activation. Because of their multiple effects on receptor- and voltage-operated cation channels, polyamines that are released by NMDA receptor activation may play an important role in phenomena already attributed to NMDA receptor stimulation, such as long-term potentiation, synaptic plasticity, and neurotoxicity.

Difluoromethyl ornithine protects against the neurotoxic effects of intrastriatally administered N-methyl-D-aspartate in vivo

The neurotoxic effects of intrastriatally administered N-methyl-D-aspartate (NMDA) (250 nmol), as measured by reductions in striatal choline acetyl transferase activity and by increased binding of the glial marker [3H]PK 11195 10 days later, were reduced by coinfusion of the irreversible ornithine decarboxylase inhibitor difluoromethylornithine (250 nmol) in the rat. The data suggest a crucial role for the polyamines in NMDA receptor-mediated neurotoxicity.

The effects of N-methyl-D-aspartate and kainate lesions of the rat striatum on striatal ornithine decarboxylase activity and polyamine levels

The intrastriatal injection of N-methyl-D-aspartate (NMDA) (250 nmol) produced a delayed and marked increase in striatal ornithine decarboxylase (ODC) activity and putrescine levels which peaked 6-15 h following the injection of NMDA. Striatal ODC activity subsequently returned to normal values while putrescine levels remained significantly elevated for up to 4 days following the lesion. NMDA produced an early and progressive decline in striatal spermine and spermidine levels, preceding the increase in ODC activity, with a maximum effect 2 h following injection. Spermidine levels returned to normal 6 h post-NMDA infusion, and subsequently increased to above normal levels 36 h and 4 days after the infusion of NMDA. This late increase in striatal spermidine levels paralleled an increase in the binding of the glial cell/macrophage marker [3H]PK 11195. Spermine levels tended to return to normal values 6 h after the injection of NMDA but may be further depressed at later intervals (15 h to 4 days). The intrastriatal injection of saline also resulted in a delayed increase in striatal ODC activity and putrescine levels, but these changes were minor compared to those produced by NMDA. Intrastriatal saline injection provoked no consistent change in striatal spermine or spermidine levels. The changes in polyamine metabolism produced by the intrastriatal injection of kainic acid (4 nmol) were only analysed at 6 and 15 h following injection but were qualitatively similar to those produced by NMDA although perhaps following a slightly more delayed time-course.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of pharmacological manipulation on neurotransmitter and other amino acid levels in the CSF of the Senegalese baboon Papio papio

The concentrations of GABA, glutamate, aspartate, glycine, taurine, glutamine, asparagine and alanine were determined in the CSF of 10 Senegalese baboons (Papio papio) following initial ketamine anaesthesia and subsequent administration (4 h later) of different compounds known to alter either inhibitory or excitatory neurotransmission. Ketamine itself was apparently without effect as the administration of a second dose of ketamine did not significantly alter the levels of any of the amino acids studied, although GABA levels tended to decrease. The presence of haemolysed material in occasional samples was associated with high GABA, glutamate, aspartate, taurine and asparagine levels. Therefore only haemolysate-free samples were included for analysis. Of the compounds administered, gamma-vinyl GABA had the most evident effect on CSF amino acid levels, increasing GABA (greater than 5-fold) and decreasing glutamate (greater than 50%), aspartate (40-50%), asparagine (20%) and alanine (30-35%) levels. The changes in GABA, glutamate and aspartate were still apparent 24 h post-gamma-vinyl GABA administration. In contrast, sodium valproate did not significantly alter the CSF levels of any of the amino acids studied. Upon acute administration allylglycine decreased the CSF concentrations of GABA and alanine, but not glutamate. These alterations are unlikely related to the occurrence of allylglycine-induced convulsions (in 2 of 4 experiments) as electroconvulsive shock did not alter CSF amino acid levels. During the experimental period encompassing the allylglycine injection (8 weeks), basal (initial post-ketamine, pre-drug sample) amino acid levels were abnormal with large increases in glutamate, GABA, aspartate and taurine whereas asparagine levels were below the limit of detection. Diazepam administration was followed by a significant increase in taurine and a decrease in aspartate levels.(ABSTRACT TRUNCATED AT 250 WORDS)

[Value of hormonal treatment with triiodothyronine and cortisone in brain dead patients]

Brain death leads to substantial falls in the plasma levels of cortisol and tri-iodothyronine (T3). These alterations may be responsible for physiological instability in these patients, and impairment in donor organ function. A double-blind study was therefore designed to assess the possible improvement in metabolism and haemodynamic stability in brain-dead organ donors treated with T3 and cortisone. Forty adult brain-dead patients were randomly assigned to two groups, the patients of the treated group were given every hour, or half hour, 2 or 4 micrograms T3 and 100 mg hydrocortisone intravenously, and those of the placebo group normal saline. Both groups of patients received conventional management for brain-dead donors. The main assessment criterion was the haemodynamic course, appreciated by the Pasys, the CVP and the needs in dobutamine; the secondary criterion was the start, or worsening, of a metabolic acidosis, as judged by the pH, the level of arterial bicarbonate, and the needs in sodium bicarbonate. The two groups were comparable for age, sex, aetiology of brain death, the delay between brain death and the start of the experimental protocol, and the duration of this protocol. There were differences between the two groups, which were not statistically significant: improvement in haemodynamic profile (hormone group 9/20 versus placebo group 10/20); worsening in haemodynamic profile (2/20 vs 4/20); increased requirements in dobutamine (2/20 vs 4/20); decreased requirements in inotropic support (15/20 vs 13/20); mean dose of dobutamine (3.1 +/- 4.2 micrograms.kg-1 vs 2.5 +/- 3.8 micrograms.kg-1); metabolic acidosis (5/20 vs 5/20); mean bicarbonate dose (30.0 +/- 67.7 mmol vs 45.0 +/- 74.2 mmol); donors harvested (20/20 vs 18/20).(ABSTRACT TRUNCATED AT 250 WORDS)

[Measurement of cardiac output by thoracic electrical bioimpedance or thermodilution]

The present study was designed to assess a new non invasive method for measuring cardiac output. The thoracic electrical bioimpedance method was compared with the reference one, thermodilution. The measurements were made simultaneously with NCCOM3 (bioimpedance) using the freeze data mode, and with a Swan-Ganz catheter and a haemodynamic computer (thermodilution). The study involved 11 spontaneously breathing patients in a steady haemodynamic state. Ten measurements were carried out with both methods for each patient. Statistical analysis of the 110 paired values was carried out by computer. The various statistical tests applied confirmed that there was a highly significant correlation between values for cardiac output obtained by each of these two methods (r = 0.818; p less than 0.005); they also showed a significantly more important dispersion of the measures for each patient with thermodilution. The mean value of the thermodilution "standard deviation" (0.64 l.min-1) was significantly more important (p less than 0.005) than the one with NCCOM3 (0.24 l.min-1). Thoracic electrical bioimpedance appeared a safe method for measuring cardiac output, providing the limits of the method are kept. The objective is not to replace the Swan-Ganz catheter, but to propose an alternative method for measuring cardiac output. This method is very interesting in many circumstances, particularly for intensive care patients: it is a non invasive technique, continual measurement is not time-limited, and its use is very easy.

[Pneumonia, disseminated intravascular coagulation and colonic hematoma]

A case of pneumopathy associated with a colonic haematoma and a disseminated intravascular coagulation is reported. No bacteriological or serological evidence of the infection could be found. The rarity of such a pathological association made this case particularly interesting.