Low whole-blood S-adenosylmethionine and correlation between 5-methyltetrahydrofolate and homocysteine in coronary artery disease

Mild elevation of plasma homocysteine is an independent risk factor for vascular disease. We studied the role of 5-methyltetrahydrofolate (5-MTHF), the folate form directly involved in homocysteine metabolism, in contrast to previous studies, which used total folate measurements, in 70 coronary artery disease (CAD) patients and control subjects. We also measured S-adenosylmethionine (SAM), which controls the activity of critical enzymes of homocysteine metabolism. Fasting plasma total homocysteine was elevated (> 12.4 mumol/L for women, > 13.3 mumol/L for men) in 17% of patients, in accordance with earlier studies. These patients showed lower 5-MTHF (12.4 +/- 1.0 mumol/L, mean +/- SD) than control subjects (24.2 +/- 15.0, P < .001), and there was a clear correlation (multiple linear regression analysis: P = .002) of this relevant form of folate with homocysteine. However, 37% of the normohomocysteinemic patients also revealed similarly low 5-MTHF levels, suggesting that a decrease of 5-MTHF does not necessarily cause hyperhomocysteinemia. SAM was significantly decreased in patients (1.4 +/- 0.4 mumol/L) compared with control subjects (1.8 +/- 0.3, P < .001) but was not correlated to homocysteine or 5-MTHF. The correlation between homocysteine and 5-MTHF that was found in CAD patients but not in control subjects confirms the direct relationship between these compounds in vivo. The new finding of low SAM in patients demands further studies, since it might indicate that low levels pose risk and that SAM might be a protective factor against the development of CAD.

Vertical signal flow and oscillations in a three-layer model of the cortex

A model of vertical signal flow across a layered cortical structure is presented and analyzed. Neurons communicate through spikes, which evoke an excitatory or inhibitory postsynaptic potential (spike response model). The layers incorporate two anatomical features-dendritic and axonal arborization patterns and distance-dependent time delays. The vertical signal flow through the network is discussed for various stimulus conditions using two different, but typical, axonal arborization patterns. We find stationary as well as oscillatory response, but the oscillatory response may be restricted to a single layer. Confronted with conflicting stimuli the network separates the patterns through phase-shifted oscillations. We also discuss two hypothetical animals, to be called "cat" and "mouse." These have different axonal arborizations, which give rise to a different oscillatory response (if any) of the various layers.

[Heparin-induced thrombopenia and thrombosis]

Heparin-induced thrombocytopenia (HIT) with thrombosis is a rare, but important complication of heparin therapy. We describe the case of a 53-year-old patient hospitalized with complicated pelvic fracture. Intravenous infusion of unfractionated heparin (15'000 IU/24 h) was given for thrombosis prevention. After 11 days' treatment the patient developed deep venous thrombosis of the left calf, complicated 2 days later by massive bilateral pulmonary embolism. Simultaneous with these thromboembolic events, thrombocytopenia, signs of activated coagulation, and antibodies to heparin occurred. In the context of this case the diagnostic and therapeutic possibilities of HIT, and in particular treatment with the heparinoid danaproid (Orgaran), are discussed.

Tracheal gas insufflation-pressure control versus volume control ventilation. A lung model study

Tracheal gas insufflation (TGI) has been recommended as an adjunct to mechanical ventilation in the presence of elevated Pa CO2. Based on our initial clinical experience with continuous flow TGI and pressure control ventilation (PCV), we were concerned about elevation in peak airway pressure as TGI was applied. In a lung model, we evaluated the effects of continuous flow TGI during both PCV and volume control ventilation (VCV). A single compartment lung model was configured with an artificial trachea into which an 8-mm endotracheal tube was positioned. TGI was established with a 16-G catheter positioned 2 cm beyond the tip of the endotracheal tube. Ventilation was provided by a Puritan-Bennett 7200ae ventilator with PCV 20 cm H2O or VCV with a tidal volume (VTt) similar to that with PCV. A rate of 15 breaths/min and PEEP of 10 cm H2O were used throughout. Inspiratory times (TI) of 1.0, 1.5, 2.0, and 2.5 s were used with TGI of 0, 4, 8, and 12 L/min. Lung model compliance (ml/cm H2O) and resistance (cm H2O/L/s) combinations of 20/20, 20/5, and 50/20 were used. Auto-PEEP, VT, and peak alveolar and airway opening pressures increased as TGI and Ti increased, regardless of lung mechanics settings (p<0.01). All increases were greater with VCV than PCV (p<0.05). Continuous flow TGI with both PCV and VT-uncorrected VCV may result in marked increases in Vt and system pressures, especially at long TI.

Intracellular Ca2+ stores can account for the time course of LTP induction: a model of Ca2+ dynamics in dendritic spines

1. A model of Ca2+ dynamics in spines of CA1 hippocampal neurons is presented. In contrast to traditional models, which concentrate on the effects of Ca2+ influx, diffusion, buffering, and extrusion, we also consider the additional effect of intracellular Ca2+ stores. 2. It is shown that traditional models without Ca2+ stores cannot account for the time course of long-term potentiation (LTP) induction as found in recent experiments. Experimental data suggest that the intracellular Ca2+ concentration should be elevated for up to 2 s, whereas the Ca2+ concentration in standard models of Ca2+ dynamics decays much faster. 3. When intracellular Ca2+ stores are taken into account, a much slower decay is found. In particular, a model simulation with a stimulation paradigm consisting of two bursts of four impulses at 100 Hz each and variable interburst intervals can reproduce experimental results found for primed or theta-burst stimulation. 4. In our model, Ca2+ release from the store has a nonlinear, bell-shaped dependence on the intracellular Ca2+ concentration, similar to the one found for inositoltrisphosphate and ryanodine receptors. These receptors are known to control calcium release from intracellular stores. 5. Our model suggests an important role of intracellular calcium stores in the induction of LTP. The stores serve as a long-term calcium source that can sustain an intracellular Ca2+ concentration above the resting level for 1-2 s.

Spontaneous excitations in the visual cortex: stripes, spirals, rings, and collective bursts

As a simple model of the cortical sheet, we study a locally connected net of spiking neurons. Refractoriness, noise, axonal delays, and the time course of excitatory and inhibitory postsynaptic potentials are taken into account explicitly. In addition to a low-activity state and depending on the synaptic efficacy, four different scenarios evolve spontaneously, viz., stripes, spirals, rings, and collective bursts. Our results can be related to experimental observations of drug-induced epilepsy and hallucinations.

Influence of carbon monoxide (CO) on the early course of acute myocardial infarction

OBJECTIVE

To clarify the influence of an elevated carboxyhemoglobin (COHb) blood level on the course of acute myocardial infarction and to evaluate the administration of supplemental oxygen on the COHb level and the incidence of complications.

DESIGN

Prospective clinical study with randomized, unblinded intervention.

SETTING

Coronary Care Unit of a university hospital.

PATIENTS

78 consecutive patients with acute myocardial infarction. Excluded were patients with severe dyspnea, pulmonary edema or any other medical indication for supplemental oxygen therapy.

INTERVENTIONS

Randomized therapy with 41/min oxygen in 35 patients.

MEASUREMENTS AND RESULTS

COHb was measured at admission and 4 h later. The incidence of serious arrhythmias and the maximal creatine kinase (CK) values were recorded. In patients with initial COHb > or = 5%, there were significantly more arrhythmias and significantly higher maximal CK values than in those with normal COHb admission (89 vs 33%, p < 0.001; and 1897 +/- 1602 u/l vs 960 +/- 1097 u/l, p=0.05). This effect was seen only in patients with Q-wave infarction, not in those with non-Q-wave infarction. Supplemental oxygen had no effect on the incidence of arrhythmias.

CONCLUSIONS

We conclude that myocardial infarction patients with acute Q-wave infarction and increased COHb levels at admission suffer a more severe course of the disease. This outcome was not influenced by oxygen therapy. Whether this finding indicates a casual relationship and whether higher oxygen concentrations would favorably alter the course of acute myocardial infarction remains to be determined.

Prolonged sedation due to accumulation of conjugated metabolites of midazolam

Midazolam is a short-acting benzodiazepine routinely used in intensive-care medicine. Conjugates of its main metabolite, alpha-hydroxymidazolam, have been shown to accumulate in renal failure but have not previously been related to the prolonged sedative effects commonly observed in critically ill patients. We report five patients with severe renal failure who had prolonged sedation after administration of midazolam. In all five patients, the comatose state was immediately reversed by the benzodiazepine-receptor antagonist flumazenil. Serum concentration monitoring showed high concentrations of conjugated alpha-hydroxymidazolam when concentrations of the unconjugated metabolite and the parent drug were below the therapeutic range. In-vitro binding studies showed that the affinity of binding to the cerebral benzodiazepine receptor of glucuronidated alpha-hydroxymidazolam was only about ten times weaker (affinity constant 16 nmol/L) than that of midazolam (1.4 nmol/L) or unconjugated alpha-hydroxymidazolam (2.2 nmol/L). Conjugated metabolites of midazolam have substantial pharmacological activity. Physicians should be aware that these metabolites can accumulate in patients with renal failure.

[Diagnostic and therapeutic consequences of pulmonary artery catheters. Prospective evaluation in an intensive care unit]

BACKGROUND

The diagnostic value and the therapeutic impact of pulmonary artery catheters have been repeatedly challenged. As part of a quality assurance project we compared clinical assessment with invasive measurements of hemodynamic parameters in critically ill patients and assessed changes in therapy following catheter insertion.

METHODS

In 47 consecutive patients (age 31-79 years; mean APACHE-II score 19 +/- 8) of a medical intensive care unit both physicians and intensive care nurses independently estimated mean pulmonary arterial pressure (PAPm), pulmonary capillary wedge pressure (PCWP), and cardiac output (CO) prior to pulmonary artery catheterization based on available clinical and radiological information. The physician-in-charge had to specify a presumptive treatment strategy in case hemodynamic measurements were not available.

RESULTS

In 19% minor complications due to catheter insertion occurred, only one requiring intervention (intravenous adenosine). Overall, PAPm was correctly predicted in 56%, PCWP in 51% and CO in 50% of the patients (Z > 2.6; p < 0.01 for all 3 parameters). There was no statistically significant difference in the percentage of correct predictions between physicians of different training levels or between physicians and nurses. In patients with sepsis the clinical prediction of PAPm (37% correct) and of PCWP (37%) was probably not better than by chance alone (Z = 1.53; p = 0.06). In 21% there was a major change in treatment after obtaining the invasive hemodynamic values compared to the preinsertion plan.

CONCLUSIONS

Although randomized trials have not yet shown pulmonary artery catheterization to decrease mortality in critically ill patients, possible useful effects on intermediate outcomes cannot be excluded in view of the high numbers of misjudgements based on clinical information alone and the considerable number of changes in therapy following catheter insertion. Reducing uncertainty in clinical judgement may not in every case lead to a beneficial strategy, but it may prevent potentially harmful decisions.

Nitrogen dioxide production during mechanical ventilation with nitric oxide in adults. Effects of ventilator internal volume, air versus nitrogen dilution, minute ventilation, and inspired oxygen fraction

BACKGROUND

Inhaled nitric oxide (NO) may be useful in the treatment of adult respiratory distress syndrome and other diseases characterized by pulmonary hypertension and hypoxemia. NO is rapidly converted to nitrogen dioxide (NO2) in oxygen (O2) environments. We hypothesized that in patients whose lungs are mechanically ventilated and in those with a long residence time for NO in the lungs, a clinically important [NO2] may be present. We therefore determined the rate constants for NO conversion in adult mechanical ventilators and in a test lung simulating prolonged intrapulmonary residence of NO.

METHODS

NO (800 ppm) was blended with nitrogen (N2), delivered to the high-pressure air inlet of a Puritan-Bennett 7200ae or Siemens Servo 900C ventilator, and used to ventilate a test lung. The ventilator settings were varied: minute ventilation (VE) from 5 to 25 l/min, inspired O2 fraction (FIO2) from 0.24 to 0.87, and [NO] from 10 to 80 ppm. The experiment was then repeated with air instead of N2 as the dilution gas. The effect of pulmonary residence time on NO2 production was examined at test lung volumes of 0.5-4.0 l, VE of 5-25 l/min, FIO2 of 0.24-0.87, and [NO] of 10-80 ppm. The inspiratory gas mixture was sampled 20 cm from the Y-piece and from within the test lung. NO and NO2 were measured by chemiluminescence. The rate constant (k) for the conversion of NO to NO2 was determined from the relation 1/[NO]t-1/[NO]o = k x [O2] x t, where t = residence time.

RESULTS

No NO2 was detected during any trial with VE 20 or 25 l/min. With N2 dilution and the Puritan-Bennett 7200ae, NO2 (< or = 1 ppm) was detected only at a VE of 5 l/min with an FIO2 of 0.87 and [NO] > or = 70 ppm. In contrast, [NO2] values were greater with the Servo 900C ventilator than with the Puritan-Bennett 7200ae at similar settings. When NO was diluted with air, clinically important [NO2] values were measured with both ventilators at high [NO] and FIO2. Rate constants were 1.46 x 10(-9) ppm-2.min-1 when NO was mixed with N2, 1.17 x 10(-8) ppm-2.min-1 when NO was blended with air, and 1.44 x 10(-9) ppm-2.min-1 in the test lung.

CONCLUSIONS

[NO2] increased with increased FIO2 and [NO], decreased VE, blending with air, and increased lung volumes. Higher [NO2] was produced with the Servo 900C ventilator than the Puritan-Bennett 7200ae because of the greater residence time. With long intrapulmonary residence times for NO, there is a potential for NO2 production within the lungs. The rate constants determined can be used to estimate [NO2] in adult mechanical ventilation systems.

[Acute pulmonary embolism]

Pulmonary embolism is a frequent event, even today the diagnostic comes often too late or not at all. Symptoms, clinical results and additional examinations like ECG, echocardiography, scintigraphy and angiography permit the differentiation between small peripheral and massive central pulmonary embolism [PE], important for the therapeutic procedure. Patients with peripheral PE have to be heparinized, sometimes they can be treated at home. The acute massive PE represents an emergency situation, the patient must be hospitalized immediately. The goals of therapy in massive PE consist in a rapid reduction of the threatening load on the right ventricule by the embolism. If the patient is in cardiogenic shock, surgical embolectomy is indicated, without shock the immediate start of thrombolytic therapy must be considered.

Cardiorespiratory effects of volume- and pressure-controlled ventilation at various I/E ratios in an acute lung injury model

Numerous approaches to the provision of mechanical ventilation during acute lung injury are currently available. Of these, pressure control inverse ratio ventilation has been considered superior to volume control ventilation with PEEP with respect to improving gas exchange and minimizing cardiovascular compromise. However, no study systematically compares volume-controlled (VC) and pressure-controlled (PC) ventilation while maintaining mean airway pressure (MAP) constant at varying I/E ratios. We studied the effect of VC and PC with PEEP at normal (1:2) and inverse I/E ratios (2:1 and 4:1) on gas exchange, lung mechanics, and hemodynamics in a sheep lung injury model. Severe lung injury was induced in 12 sheep with bilateral lung lavages using normal saline; prelavage PO2 230 +/- 50 mm Hg, PEEP 5 cm H2O and postlavage, pretreatment PO2 70 +/- 20 mm Hg, PEEP 10 cm H2O, both at FIO2 0.50. MAP was kept constant throughout the study at 25 +/- 2 cm H2O while ventilating all animals with a VT of 10 ml/kg and a rate of 20/min by randomized application of VC and PC with I/E ratios of 1:2, 2:1, and 4:1. Despite liberal fluid administration, all ventilatory modes depressed cardiac output compared with preinjury values. However, gas exchange and hemodynamics did not differ among ventilation modes or I/E ratios.(ABSTRACT TRUNCATED AT 250 WORDS)

N-acetylcysteine enhances recovery from acute lung injury in man. A randomized, double-blind, placebo-controlled clinical study

OBJECTIVE

To determine the effects of intravenous N-acetylcysteine (NAC) on the development of severe adult respiratory distress syndrome (ARDS) and mortality rate in patients with mild-to-moderate acute lung injury and to analyze the duration of ventilatory support and FIO2 required as well as the evolution of the lung injury score.

SETTING

Three university hospital ICUs and one regional ICU in Switzerland.

PATIENTS

Sixty-one adult patients presenting with mild-to-moderate acute lung injury and various predisposing factors for ARDS received either NAC, 40 mg/kg/d, or placebo intravenously for 3 days.

MEASUREMENTS

Respiratory dysfunction was assessed daily according to the need for mechanical ventilation and FIO2, the evolution of the lung injury score, and the PaO2/FIO2 ratio. The cardiovascular state, liver function, and kidney function were also monitored. Data were collected at admission (day 0), during the first 3 days, and on the day of discharge from the ICU.

RESULTS

The NAC and placebo groups (32 and 29 patients, respectively) were comparable at ICU admission for severity of illness assessed by the simplified acute physiology score (SAPS) (10.8 +/- 4.6 vs 10.9 +/- 4.8) and lung injury score (LIS) (1.39 +/- 0.95 vs 1.11 +/- 1.08) (mean +/- SD). Three patients in each group developed ARDS. The 1-month mortality rate was 22 percent for the NAC group and 35 percent for the placebo group (difference not statistically significant). At admission, 22 of 32 patients (69 percent) in the NAC group were mechanically ventilated compared with 22 of 29 (76 percent) in the placebo group. At the end of the treatment period (day 3), 5 of 29 (17 percent) in the NAC group and 12 of 25 (48 percent) in the placebo group were still receiving ventilatory support (p = 0.01), The FIO2 was 0.37 less than admission value (day 0) in the NAC group, and 0.20 less in the placebo group (p < 0.04); the oxygenation index (PaO2/FIO2) improved significantly (p < 0.05) from day 0 to day 3 only in the NAC-treated group. The LIS showed a significant regression (p = 0.003) in the NAC-treated group during the first 10 days of treatment: no change was observed in the placebo group. No adverse effects were observed during the treatment with NAC.

CONCLUSIONS

Intravenous NAC treatment during 72 h improved systemic oxygenation and reduced the need for ventilatory support in patients presenting with mild-to-moderate acute lung injury subsequent to a variety of underlying diseases. Development of ARDS and mortality were not reduced significantly by this therapy.

A biologically motivated and analytically soluble model of collective oscillations in the cortex. II. Application to binding and pattern segmentation

Feature linking and pattern separation are shown to be performed as simultaneous processes by a highly connected auto-associative network of spiking neurons (spike response model). In principle, many (e.g., with nine) patterns can be separated, but with a biological set of parameters the number is limited to four. The patterns have been learned by an asymmetric hebbian rule that can handle a low activity which may vary from pattern to pattern (in a range between 4% and 7%). Spikes are generated by a threshold process and--with some delay--transmitted to postsynaptic neurons. There they evoke an excitatory or inhibitory postsynaptic potential (EPSP or IPSP). Spike emission is followed by an absolute refractory period (1 ms) and activates an inhibitory delay loop that prevents continuous firing. Three different network topologies are discussed, i.e., a structureless fully connected system, a network composed of two 'hemispheres', and finally a hierarchical network with four subsystems that represent different 'functions' and interact via feedforward and feedback connections. Functional feedback turns out to be essential for context-sensitive binding. The coherence between the two hemispheres is dependent on the interhemispheric delays. If these are on average too large, the two hemispheres oscillate coherently by themselves but phase-shifted by half a period with respect to each other.

Evaluation of conventional chest tube therapy for iatrogenic pneumothorax

STUDY OBJECTIVE

To assess conventional, large chest tube therapy in iatrogenic pneumothorax and to determine the optimal moment when to use more invasive procedures.

DESIGN

Retrospective chart review.

SETTING

Medical intensive care unit of a university hospital.

PATIENTS

Forty-seven patients with needle-induced iatrogenic pneumothorax. Twenty-four patients had an underlying pleural or pulmonary disorder.

INTERVENTIONS

After insertion of a 20- to 24-French plastic chest tube connected to an underwater seal, suction was maintained until gas egress stopped or up to 10 days in patients with a persisting gas leak.

RESULTS

In 96 percent, a definite occlusion of the pneumothorax was achieved. In all patients without an underlying lung disorder, gas egress stopped definitely after 72 h. In the presence of an underlying lung disorder, 92 percent of the pneumothoraces were healed after 10 days of continuous suction therapy. At 72 h, only 71 percent of the latter group were healed (p < 0.05 vs patients without lung disease). No major complication of chest tube therapy occurred.

CONCLUSION

Conventional chest tube therapy is a safe and effective treatment for iatrogenic pneumothorax. In patients with an underlying lung disease, gas egress may last for up to 10 days. In these patients, the earlier use of a more invasive approach may be justified if the air leak persists.

Comparison of Texas Liquid Sampler with Missouri Bottle for Sampling Liquid Fertilizers: Collaborative Study

Six laboratories participated in a collaborative study designed to qualify the Texas liquid sampling tube as a device for sampling liquid fertilizers. The Texas sampler is a polyethylene tube with a stainless steel check valve on one end. The tube, which is threaded so that it can be expanded in length, enables acquisition of a uniform profile across a liquid sample. The 6 collaborators sampled 33 loads of fertilizer, 8 of which were slurries, using both the Texas tube and the Missouri bottle (AOAC 969.01). The resulting subsamples were analyzed for total nitrogen, available phosphorus, and soluble potash. Analysis of the data showed no significant (p &lt; 0.05) difference in results. This sampling procedure, using the Texas liquid sampler, was adopted first action by AOAC International as a suitable means of sampling liquid fertilizers.

Determinants of survival after rodent cardiac arrest: implications for therapy with adrenergic agents

Coronary perfusion pressure and its relation with the expired carbon dioxide concentration (end-tidal CO2) was examined in a rodent model of sustained ventricular fibrillation and subsequent cardiopulmonary resuscitation. Equipressor dosages of the pure alpha 1-agonist methoxamine, the mixed alpha/beta-agonists epinephrine and norepinephrine were randomly compared with 0.9% NaCl. Thirty two Sprague-Dawley rats were anesthetized and catheters were advanced into the aorta, right ventricle, right atrium and inferior vena cava. After 4 min of untreated ventricular fibrillation external chest compression was initiated and defibrillation was attempted after 8 min. Drugs were infused for 3 min during cardiopulmonary resuscitation into the inferior vena cava. A 60-min survival period followed methoxamine administration in 7 of 8 (P < 0.019 vs. NaCl), after epinephrine in 4 of 8, after norepinephrine in 5 of 8, and after NaCl in only 2 of 8 animals. Resuscitation success was determined by coronary perfusion and mean aortic pressures generated during cardiopulmonary resuscitation but not by arterial or venous blood gases. Adrenergic agents increased coronary perfusion and mean aortic pressures but decreased end-tidal CO2 which failed to correlate with these pressures. Accordingly, alpha-adrenergic agents mitigated the accuracy of end-tidal CO2 as a non-invasive hemodynamic monitor and predictor of survival after rodent cardiopulmonary resuscitation.

Gender and response to antilymphocyte globulin (ALG) for severe aplastic anaemia

We have evaluated the speed of haematological recovery in 103 severe aplastic anaemia (SAA) patients treated with antilymphocyte globulin (ALG) and followed at our institution for 3-15 years. We found that haemopoietic recovery was significantly delayed in six girls under the age of 10 years. This slow recovery in girls might be explained by their relative inability to release haemopoietic growth factors, granulocyte colony stimulating activity and burst promoting activity, compared to all other sex and age groups. This defect is not explained by disease severity at presentation and thus indicates a functional abnormality of monocytes/macrophages and T-lymphocytes in addition to the deficiency of haemopoietic stem cells. In a multivariate analysis, low factor production and low pretreatment reticulocyte counts turned out to be strong predictors of slow haemopoietic recovery. We conclude that young girls have a particular form of SAA characterized by low haemopoietic factor production and delayed recovery after ALG. They are preferential candidates for early bone marrow transplantation or, if they are not eligible, for treatment with recombinant human haemopoietic growth factors.

[Factor VII and protein-C markers are no prognostic indicators in acute coronary heart disease]

Fibrinogen and factor VII have been identified as independent risk factors in cardiovascular morbidity. A relationship between factor VII coagulant activity (VII:C) and prognostically different manifestations of acute coronary heart disease (aCHD) has recently been suggested. In order to validate and to extend these observations, we prospectively studied patients admitted for aCHD (n = 76) and a control group without aCHD (CG, n = 27). According to their clinical evolution, the aCHD cases were subdivided into unstable angina (UA, n = 26), myocardial infarction without (M-I, n = 23) and with heart failure (M-II, n = 27). Before treatment blood was collected for the following assays: fibrinogen, factor VII procoagulant activity (VII:C), amidolytic test (VII:am), immunological (VII:Ag), protein C functional (PCf) and immunological (PC:Ag). We found no statistically significant difference between control and aCHD cases and between their subgroups for any assay of fibrinogen, factor VII and protein C. The VII:C/VII:Ag ratio was higher for UA, M-I, M-II and the entire aCHD group compared with the CG. However, it was not possible to separate the prognostically different aCHD subgroups from each other by ratios of measured values. Therefore, determinations of factor VII, protein C and fibrinogen in aCHD have no prognostic relevance.

A biologically motivated and analytically soluble model of collective oscillations in the cortex. I. Theory of weak locking

A model of an associative network of spiking neurons with stationary states, globally locked oscillations, and weakly locked oscillatory states is presented and analyzed. The network is close to biology in the following sense. First, the neurons spike and our model includes an absolute refractory period after each spike. Second, we consider a distribution of axonal delay times. Finally, we describe synaptic signal transmission by excitatory and inhibitory potentials (EPSP and IPSP) with a realistic shape, that is, through a response kernel. During retrieval of a pattern, all active neurons exhibit periodic spike bursts which may or may not be synchronized ('locked') into a coherent oscillation. We derive an analytical condition of locking and calculate the period of collective activity during oscillatory retrieval. In a stationary retrieval state, the overlap assumes a constant value proportional to the mean firing rate of the neurons. It is argued that in a biological network an intermediate scenario of 'weak locking' is most likely.

Why spikes? Hebbian learning and retrieval of time-resolved excitation patterns

Hebbian learning allows a network of spiking neurons to store and retrieve spatio-temporal patterns with a time resolution of 1 ms, despite the long postsynaptic and dendritic integration times. To show this, we introduce and analyze a model of spiking neurons, the spike response model, with a realistic distribution of axonal delays and with realistic postsynaptic potentials. Learning is performed by a local Hebbian rule which is based on the synchronism of presynaptic neurotransmitter release and some short-acting postsynaptic process. The time window of this synchronism determines the temporal resolution of pattern retrieval, which can be initiated by applying a short external stimulus pattern. Furthermore, a rate quantization is found in dependence upon the threshold value of the neurons, i.e., in a given time a pattern runs n times as often as learned, when n is a positive integer (n > or = 0). We show that all information about the spike pattern is lost if only mean firing rates (temporal average) or ensemble activities (spatial average) are considered. An average over several retrieval runs in order to generate a post-stimulus time histogram may also deteriorate the signal. The full information on a pattern is contained in the spike raster of a single run. Our results stress the importance, and advantage, of coding by spatio-temporal spike patterns instead of firing rates and average ensemble activity. The implications regarding modelling and experimental data analysis are discussed.

[Cocaine poisoning from transport of the drug in the gastrointestinal tract (the body-packer syndrome)]

Three days after arriving in Switzerland from Bolivia a 35-year-old man presented at a casualty department. He was anxious, agitated and hallucinating, and he expressed delusional ideas of being poisoned. As a general physical examination was without abnormal findings he was thought to suffer from a psychiatric disorder. It was only when he had evacuated in stool a long oval foreign body, packed in plastic sheeting and filled with a dark paste, that cocaine poisoning due to cocaine transport in the gastrointestinal tract (body packer syndrome) was suspected. Plain X-ray of the abdomen revealed numerous regular structures of poor X-ray contrast and the urine contained cocaine metabolites, confirming the tentative diagnosis. As the patient's state of consciousness deteriorated and he had a grand mal seizure, an emergency laparotomy was performed. 78 packages (two of them had opened) were removed by gastro- and caecotomy. Total cocaine weight was 650 g. He was discharged from hospital after 11 days, free of symptoms.

Rapid reversal of heart failure in a patient with phaeochromocytoma and catecholamine-induced cardiomyopathy who was treated with captopril

A patient with a phaeochromocytoma and severe left ventricular heart failure caused by a catecholamine-induced cardiomyopathy is described. The clinical signs of congestive heart failure resolved rapidly on treatment with captopril and myocardial performance became normal within two weeks of medical treatment with captopril for one week and with captopril in combination with phenoxybenzamine for another week.