P1392 Association of iron deficiency with left ventricular longitudinal function abnormalities in patients with acute myocarditis

Background

Recent evidence suggests that iron depletion may be involved in the pathophysiology of acute myocarditis (MCD), however no data on the contribution of this mechanism to the MCD-associated cardiac performance abnormalities are available. The decrease in longitudinal deformation is an early manifestation of left ventricular (LV) dysfunction. Nonetheless, global longitudinal strain (GLS) is afterload-dependent, and the estimation of myocardial work correcting GLS for changes in systolic blood pressure may permit a more adequate assessment of LV contractility.

Aim

We sought to investigate the association between iron status and LV function in patients with MCD.

Methods

We prospectively included 30 patients (age 32 ± 8 years; 97% male) hospitalized for acute MCD in a tertiary cardiology center. MCD was diagnosed based on the following criteria: 1) new onset symptoms suggestive of myocarditis (exercise intolerance, dyspnea, palpitations or chest pain), 2) elevated high sensitivity cardiac troponin I (hscTnI), 3) exclusion of obstructive coronary artery disease, 4) confirmation of myocardial oedema based on T2 mapping in cardiac magnetic resonance. On admission, each participant underwent echocardiography with LV strain and myocardial work (global work index [GWI], global constructive work [GCW], global wasted work [GWW], global work efficiency [GWE]) analysis, and laboratory assessment including the iron status markers: ferritin and transferrin saturation (TSAT). Iron deficiency (ID) was defined as transferrin saturation (TSAT) <20%; we did not use serum transferrin to categorize iron status because of the strong association of this marker with acute inflammation, which might affect the interpretation of its values.

Results

ID was found in 16 (53%) enrollees. Patients with reduced TSAT demonstrated lower GCW and GWI than their peers with normal TSAT (Table). No significant between-group differences were found for GLS, LV ejection fraction, early diastolic tissue velocity (e’) and E/e’ ratio. Both subsets did not significantly differ with respect to hemoglobin, creatinine, NT-proBNP, hscTnI and CRP. Both GWI and GCW significantly correlated with TSAT (r = 0.39, p = 0.03, and r = 0.37, p = 0.04, respectively). In multivariable analysis, after adjustment for patient age, body mass index, creatinine, hscTnI and CRP, TSAT was an independent predictor of GWI (beta = 0.40; p = 0.02) and GCW (beta = 0.38; p = 0.02).

Conclusion

In patients with MCD, ID defined as low TSAT is associated with a worse LV longitudinal performance as assessed by GCW and GWI, which might suggest a role of this pathophysiological pathway in the development of cardiac dysfunction. Myocardial work parameters seem to outperform GLS in diagnosing LV functional impairment in this clinical setting.

Abstract P1392 Figure.

P754Iron status indices (transferrin saturation, serum ferritin) in the course of acute myocarditis: relations with neurohormonal activation, cardiac dysfunction and clinical recovery

Introduction

Acute myocarditis (MCD) can progress to post-myocarditis cardiomyopathy. Immune response is the major pathophysiological trigger leading to MCD. Optimal iron status is essential for the functioning of immune cells, cardiomyocytes and cardiofibroblasts. Therefore, there are premises to consider iron metabolism as a significant modulator of complex pathophysiology of MCD.

Purpose

We aimed to assess iron status in the course of MCD and relate it with clinical and laboratory measures.

Methods

We prospectively enrolled consecutive patients hospitalized for acute MCD in 2 tertiary referral cardiology centers during 2015–2018 and followed them up for 30 weeks. MCD was diagnosed based on the following criteria: 1) new onset symptoms suggestive of myocarditis (effort intolerance, dyspnea, palpitations or chest pain), 2) elevated high sensitivity cardiac troponin I (hs-cTnI), 3) exclusion of obstructive coronary artery disease.

Results

Study group comprised 41 patients with confirmed MCD [age: 31 (26–34) years, men: 95%] and 15 healthy age- and gender-matched subjects [age: 30 (28–33) years, men: 87%]. All patients survived hospitalization and follow-up, no subject needed ventricular assist device.

Patients with MCD had lower LVEF (56±10% vs. 69±14%) and higher CRP [32 (14–8754) vs. 3 (3–3) mg/l], NT-proBNP [452 (240–877) vs. 33 (18–46) pg/ml], hs-cTnI [7.3 (3.3–12.8) vs. 0,01 (0.01–0.01) μg/l] than the control group (all p<0.001). Regarding iron status, MCD group presented higher serum ferritin [213 (121–386) vs. 135 (84–210) μg/l] and lower transferrin saturation (TSAT) [21±10 vs. 28±15%] (all p<0.05). In patients with MCD ferritin correlated with CRP (r=0.46, p<0.01), TSAT correlated neither with CRP nor with ferritin (all p>0.02).

Patients with MCD and NT-proBNP >1000 pg/ml had lower TSAT (16±8 vs. 23±9%; p<0.05) and LVEF (47±13 vs. 59±7%; p<0.001) than the remaining subjects. No difference in ferritin was observed (p>0.2). 46% of patients during acute phase of MCD had LVEF≤55% – these patients presented lower TSAT (17±8% vs. 24±10%) and higher NT-proBNP – [577 (436–1657) vs. 358 (167–499) pg/ml] (all p<0.05). After 30 weeks only in 13% patients LVEF≤55% persisted and related to lower baseline TSAT (9±1% vs. 21±9%) and higher CRP (147±113 vs. 52±40 mg/l) (all p<0.05). LVEF≤55% was not related to ferritin (both p>0.2).

After 6 weeks of follow-up patients with MCD already presented higher LVEF (61±8%; p<0.05) and haemoglobin [14.7 (14.0–15.7) g/dl], lower CRP [3 (3–3) mg/l], NT-proBNP [34 (25–67) pg/ml], hs-cTnI [0.01 (0.01–0.01)], ferritin [124 (78–168) μg/l] and higher TSAT (26±7%) (all p<0.01). There was no further change in these parameters within the next 24 weeks (all p>0.2).

Conclusions

Iron status is deranged in acute MCD. Serum ferritin is an indicator of inflammatory response, whereas TSAT relates to neurohormonal activation and cardiac dysfunction. Iron status normalizes within 6 weeks after acute phase of MCD.

Acknowledgement/Funding

This research was financially supported by the National Science Centre (Poland) grant number 2014/13/B/NZ5/03146.

EPR spectrometer for clinical applications

This article describes an EPR spectrometer specifically designed and constructed for EPR spectroscopy in humans. The spectrometer is based on a permanent magnet, suitable for measurements at 1200 MHz. The magnet has a full 50 cm gap between the poles, which facilitates accurate and comfortable placement of the subject for the EPR measurement at any location on the human body. The bridge includes features to facilitate clinical operations, including an indicator for phasing of the reference arm and a 2 level RF amplifier. Resonators with holders for each type and site of measurement have been developed that comfortably position the resonator and the patient and prevent artifacts due to motion. The initial applications for which the spectrometer has been designed are for oximetry using loops on the surface, oximetry using implanted resonators for measuring deep sites, and measurements in the teeth for determination of exposures to clinically significant doses of ionizing radiation.

Development and evaluation of biocompatible films of polytetrafluoroethylene polymers holding lithium phthalocyanine crystals for their use in EPR oximetry

Electron paramagnetic resonance (EPR) oximetry is a powerful technology that allows the monitoring of oxygenation in tissues. The measurement of tissue oxygenation can be achieved using lithium phthalocyanine (LiPc) crystals as oxygen reporters. In order to have biocompatibility for the sensing system and to assure long-term stability in the responsiveness of the system, we developed films of Teflon AF 2400 with embedded LiPc crystals. These systems can be used as retrievable inserts or parts of an implantable resonator or catheter. Atomic force microscopy studies revealed that the surface of the films was regular and planar. The response to oxygen of the sensor (EPR linewidth as a function of pO(2)) remained unchanged after implantation in mice, and was not affected by sterilization or irradiation. The use of resonators, holding LiPc embedded in Teflon AF 2400, implanted in the gastrocnemius muscle of rabbits allowed the monitoring of oxygen during several weeks. Several assays also demonstrated the biocompatibility of the system: (1) no hemolytic effect was noted; (2) no toxicity was found using the systemic injection test of extracts; (3) histological analysis in rabbit muscle in which the films were implanted for 1 week or 3 months was similar to standard polyethylene biocompatible devices. These advanced oxygen sensors are promising tools for future pre-clinical and clinical developments of EPR oximetry. These developments can be applied for other applications of biosensors where there is a need for oxygen permeable membranes.

Epidemiological and medical aspects of epilepsy in the elderly

Both the incidence and prevalence of epilepsy are high among the elderly. Cerebrovascular disease is the most common underlying cause, although as many as 25-40% of new epilepsy cases in the elderly have no obvious underlying etiology. Status epilepticus appears to occur more frequently in individuals greater than 60 years, and the morbidity and mortality of status epilepticus are significantly greater in this age group. Elderly patients with seizures, particularly complex partial seizures, present differently than younger adults, which can lead to misdiagnosis. Post-ictal confusion may last as long as 1-2 weeks in an elderly patient, as opposed to minutes in younger individuals. Adverse events are similar in symptomatology, but are more common in elderly patients and occur at lower doses and plasma drug concentrations. Neuropsychiatric disorders, such as depression and anxiety, are common in elderly patients with epilepsy, although often under-diagnosed and inadequately treated. The risk of osteoporosis is high among elderly women taking antiepileptic drugs, which underscores the importance of assessing bone health and treatment in this group. Management of the older patient with epilepsy requires an understanding of the etiologies and the medical and psychological aspects unique to this age group.

How long does it take for partial epilepsy to become intractable?

BACKGROUND

Much remains unknown about the natural history of intractable localization-related epilepsy, including how long it typically takes before intractability becomes evident. This information could guide the design of future studies, resolve certain discrepancies in the literature, and provide more accurate information about long-term prognosis.

METHODS

Individuals evaluated for resective surgery for refractory localization-related epilepsy were prospectively identified at the time of initial surgical evaluation at seven surgical centers (between 1996 and 2001). The latency time between onset of epilepsy and failure of second medication and history of remission (>/=1 year seizure-free) before surgical evaluation were examined with respect to age at onset, hippocampal atrophy, febrile seizures, and surgical site.

RESULTS

In the 333 patients included in the analysis, latency time was 9.1 years (range 0 to 48) and 26% reported a prior remission before surgery. A prior remission of >/=5 years was reported by 8.5% of study participants. Younger age at onset was strongly associated with longer latency time (p < 0.0001) and higher probability of past remission (p < 0.0001). In multivariable analyses, age at onset remained as the most important explanatory variable of both latency time and prior remission.

CONCLUSIONS

A substantial proportion of localization-related epilepsy may not become clearly intractable for many years after onset. This is especially true of epilepsy of childhood and early adolescent onset. If prospective studies confirm these findings and the underlying mechanisms behind these associations become understood, this raises the possibility of considering interventions that might interrupt such a process and some day prevent some forms of epilepsy from becoming intractable.

Kinetics of chromium(V) formation and reduction in fronds of the duckweed Spirodela polyrhiza--a low frequency EPR study

The uptake of chromate by the duckweed Spirodela polyrhiza was investigated with atomic absorption spectroscopy and the reduction of Cr(VI) to Cr(V) was measured using low frequency EPR spectroscopy. The biphasic kinetics of the uptake was fitted to parameters of a proposed kinetic model. Another model was developed to simulate chromate reduction. The first step of chromate reduction was found to be much faster than the uptake of Cr(VI) from the free space. Most probably, this step occurs already in the cell wall or on the cell membrane surface. Further reduction of Cr(V) to Cr(III) was estimated to be slower. The disappearance of the Cr(V) signal, following transfer of the plants into a Cr-free solution, lasted several tens of hours; the kinetics was mono- or biexponential depending on the length of Cr loading. The rate constants for Cr reduction in living plants were determined for the first time.

Electronically tunable surface-coil-type resonator for L-band EPR spectroscopy

The automatic frequency control (AFC) circuit in conventional electron paramagnetic resonance (EPR) spectrometers automatically tunes the microwave source to the resonance frequency of the resonator. The circuit works satisfactorily for samples stable enough that the geometric relations in the resonance structure do not change in a significant way. When EPR signals are measured during in vivo experiments with small rodents, however, the distance between the signal source and the surface-coil detector can change rapidly. When a conventional AFC circuit keeps the oscillator tuned to the resonator under those conditions, the resultant frequency change may exceed +/-5 MHz and markedly shift the position of the EPR signal. Such a shift results in unacceptable effects on the spectra, especially when the experimenter is dealing with narrow EPR lines. The animal movement also causes a mismatching of the resonator and the 50-ohm transmission line. Direct results of this mismatching are increased noise; shifts in the position of the baseline; and a high probability of overdriving the signal preamplifier with consequent loss of the EPR signal. We therefore designed, built, and tested a new surface-coil resonator using varactor diodes for tuning the resonance frequency to the fixed frequency oscillator and for capacitive matching of the resonator to the 50-ohm transmission line. The performance of the automatic matching system was tested in vivo by measuring EPR spectra of lithium phthalocyanine implanted in rats. Stability and sensitivity of the spectrometer were evaluated by measuring EPR spectra with and without the use of the automatic matching system. The overall experimental performance of the spectrometer was found to significantly improve during in vivo experiments using the automatic matching system. Excellent matching between the 50-ohm transmission line and the resonator was maintained under all experimental circumstances that were tested. This should allow us now to carry out experiments that previously were not possible.

Electronically tunable surface-coil-type resonator for L-band EPR spectroscopy

The automatic frequency control (AFC) circuit in conventional electron paramagnetic resonance (EPR) spectrometers automatically tunes the microwave source to the resonance frequency of the resonator. The circuit works satisfactorily for samples stable enough that the geometric relations in the resonance structure do not change in a significant way. When EPR signals are measured during in vivo experiments with small rodents, however, the distance between the signal source and the surface-coil detector can change rapidly. When a conventional AFC circuit keeps the oscillator tuned to the resonator under those conditions, the resultant frequency change may exceed +/-5 MHz and markedly shift the position of the EPR signal. Such a shift results in unacceptable effects on the spectra, especially when the experimenter is dealing with narrow EPR lines. The animal movement also causes a mismatching of the resonator and the 50-ohm transmission line. Direct results of this mismatching are increased noise; shifts in the position of the baseline; and a high probability of overdriving the signal preamplifier with consequent loss of the EPR signal. We therefore designed, built, and tested a new surface-coil resonator using varactor diodes for tuning the resonance frequency to the fixed frequency oscillator and for capacitive matching of the resonator to the 50-ohm transmission line. The performance of the automatic matching system was tested in vivo by measuring EPR spectra of lithium phthalocyanine implanted in rats. Stability and sensitivity of the spectrometer were evaluated by measuring EPR spectra with and without the use of the automatic matching system. The overall experimental performance of the spectrometer was found to significantly improve during in vivo experiments using the automatic matching system. Excellent matching between the 50-ohm transmission line and the resonator was maintained under all experimental circumstances that were tested. This should allow us now to carry out experiments that previously were not possible.

Developing in vivo EPR oximetry for clinical use

This paper describes the rationale for carrying out electron paramagnetic resonance (EPR) oximetry studies in human subjects in the clinical setting and the potential approaches and specific steps needed to make such studies feasible and useful. While the approach is described specifically for EPR oximetry, many of the principles may apply to the initial clinical uses of other techniques. The suggested operational approach is to have the initial applications occur in as clinically useful and simple a manner as possible, with the expectation that once the technique is introduced and accepted in the clinical setting, that more complex and/or more technically difficult applications will be able to be developed. The initial approach will be based on EPR spectroscopy at 1.2 GHz focusing on applications for which in vivo EPR provides a clearly useful approach to important clinical problems for which currently there is no good alternative method. The EPR measurements can be carried out non-invasively by measurements within 10 mm of the surface after the placement of the paramagnetic material at the site of interest, or by the placement of a needle/catheter in the site of interest for the required time period. The suggested initial clinical applications are guiding therapy for individual patients with tumors or vascular disease, by direct measurements of tissue pO2.

Small particles of fusinite and carbohydrate chars coated with aqueous soluble polymers: preparation and applications for in vivo EPR oximetry

The development of oxygen-sensitive paramagnetic materials is being pursued actively because of their potential applications in in vivo EPR oximetry. Among these materials, several charcoals and carbohydrate chars are of special interest because of their desirable EPR properties: high sensitivity of the EPR linewidth to the partial pressure of oxygen, simple EPR spectra, and high spin density. Their potential use in humans, however, is limited by the need to demonstrate that they will not lead to deleterious effects. A strategy was used to optimize the biocompatibility of the oxygen-sensitive materials by decreasing the size of the particles and coating them with suspending or surfactive agents such as arabic gum, poloxamer (Pluriol 6800), and polyvinylpyrrolidone. The coated particles of a carbohydrate char and fusinite were characterized in vitro for their size, stability, and pO2 sensitivity. The feasibility of performing pO2 measurement was examined in vivo by inducing ischemia in the gastrocnemius muscle of mice. The use of arabic gum for coating the fusinite particles preserved the pO2 sensitivity in vivo, whereas the other surfactive agents led to a loss of the pO2 sensitivity in vivo. Small particles of fusinite coated by arabic gum and intravenously administered to mice accumulated in the liver, whereas the uncoated fusinite was toxic when injected intravenously due to the large size and aggregation of the particles. Histological studies performed up to 6 months after the injection in muscles of mice did not indicate any toxicity from the materials used in the present study.

Multivariable prediction of seizure outcome one year after resective epilepsy surgery: development of a model with independent validation

PURPOSE

To identify predictors of seizure-outcome after epilepsy surgery and validate the findings in an independent series of patients. To use the results to develop a predictive model.

METHODS

Sequential patients undergoing resective surgery for medically intractable epilepsy were identified at Yale New Haven Hospital (1987-1990, group 1) and Columbia Presbyterian Hospital (1991-1994, group 2). Information about seizure outcome and predictors of outcome was obtained from medical chart review. Good seizure-outcome was defined as having been seizure-free for one year beginning with discharge from the hospital. Multiple logistic regression was used to develop a model of predictors in group 1. It was then validated in group 2.

RESULTS

There were 133 patients in group 1 and 81 in group 2. In a multivariable analysis, independent predictors of outcome in group 1 were presence of mesial temporal sclerosis based on postsurgical pathological analysis (MTS) (relative risk (RR) = 1.47), having a known underlying etiology (RR = 1.32), and partial seizures only (RR = 1.17). In group 2, the findings for each factor were similar to those in group 1: MTS, RR = 1.49; etiology, RR = 1.32; and partial seizures, RR = 1.24. Used in combination, these three factors can identify patients with nearly a 100% chance of being seizure-free (all three factors present) versus less than a 50% chance (none of the three factors present).

CONCLUSIONS

With independent validation of the findings, we can be reasonably certain that the three factors identified in this analysis are meaningful and generalizable predictors of seizure outcome following epilepsy surgery. Use of predictive models should be considered in future studies to convert study results into clinically relevant statements about a particular patient's likelihood of surgical success.

An analysis of the effects of eddy currents on L-band EPR spectra

Recently, impressive results have been obtained with EPR studies of living animals and perfused organs using low-frequency EPR. In many instances in such studies, however, there are apparent distortions of the spectra. The shapes of these spectra and theoretical considerations indicate that these effects are due to eddy currents in the moderately conductive biological materials. Therefore the effects of eddy currents produced in biological samples under typical conditions being employed for in vivo EPR studies have been systematically studied in order to determine the extent of these effects and to develop methods for compensating for these effects. The presence of eddy currents was found to decrease the Q factor and distort the shapes of the EPR spectra. The distortion of the spectra led to linewidth broadening, changes in peak heights, and shifts of the apparent center of the lines. These effects could be corrected instrumentally, but this was effective only when signals have a high S/N. The use of appropriate computer simulations, based on linear combinations of the expected absorption and dispersion signals, can effectively correct for the effects of eddy currents and provide accurate data on the parameters of EPR spectra that are needed for most or all of the analyses used in biological studies of animals and tissues at low frequencies.

In vivo oximetry using EPR and India ink

Recent advances in electron paramagnetic resonance (EPR) oximetry have established the use of the particulate materials fusinite and lithium phthalocyanine (LiPc) as probes for measurement of oxygen tensions in tissues in vivo with a sensitivity and accuracy that is relevant for studying pathophysiological processes. India ink, another potentially very useful new probe for EPR oximetry, shares the critical properties of fusinite and LiPc and has the additional advantage of already having been widely used clinically with no apparent toxicity. The line width is particularly sensitive to changes in oxygen tension of less than 30 mmHg; in this range the line broadening/unit of pO2 is much greater than that of fusinite and LiPc. Over the range of biological conditions that can occur in vivo, the response of the EPR spectrum of India ink to pO2 is independent of pH, oxidants, reductants, and the nature of the medium. In this paper we describe the relevant properties of India ink and its use to measure pO2 in vivo in experimental animals and a human subject.

Magnetic brain stimulation: safety studies

We describe short-term and long-term safety studies after low repetition rate magnetic brain stimulation in 10 normal subjects. We obtained quantitative EEG data, psychometric test results, serum prolactin and cortisol levels before and after brain stimulation. EEG and psychometric data were also obtained in 5 of these subjects 16-24 months after the initial experiment. Short- and long-term studies did not show any deleterious effects. Randt delayed recalls, however, showed a transient reduction in the score immediately after stimulation which resolved on retesting in 2 weeks. To address the question of fatigue we repeated Randt tests in 4 subjects before and after magnetic brain stimulation but without the other extensive psychometric, EEG and blood tests. Pre- and post-stimulation scores on this occasion showed no significant difference in these 4 subjects suggesting that the transient changes in the previous Randt score were related to fatigue. We conclude that single-pulse magnetic brain stimulation has no deleterious effects after magnetic brain stimulation.

Low-frequency EPR study of chromium(V) formation from chromium(VI) in living plants

The reduction of Cr(VI) by green algae and higher plants was investigated using a low-frequency EPR spectrometer equipped with an extended loop gap resonator. Incubation of algae (Spirogyra and Mougeotia) with Cr(VI) generated both Cr(V) and Cr(III). The maximum Cr(V) signal was observed in about 10 minutes. Incubation of Cr(VI) with oat, soybean, and garlic generated Cr(V). The maximum Cr(V) peak appeared after more than 10 hours of incubation, and Cr(V) was located predominantly in the roots. The Cr(V) peak exhibited hyperfine splittings of about 0.79 gauss, typical of the Cr(V) complexes with diol-containing molecules. The results suggest that the reduction of Cr(VI) to lower oxidation states by living plants may provide a detoxification pathway for Cr(VI) in ecological systems. The results also indicate that low-frequency EPR may be used to investigate the metabolism of paramagnetic metal ions in intact plants.

Physical and instrumental considerations in the use of lithium phthalocyanine for measurements of the concentration of the oxygen

The use of crystals of lithium phthalocyanine (LiPc) to measure the concentration of oxygen in vivo and in vitro by electron paramagnetic resonance leads to experimental constraints due to the very narrow EPR lines that may occur (as narrow as 11-13 mG in the absence of O2), distortions induced by the automatic frequency control system, anisotropy in the spectra (orientation-dependent linewidth is 11-17 mG in the absence of O2), microwave power saturation, and the effect of physiological motion. These constraints can be overcome if recognized. This article highlights the experimental and theoretical basis of these properties of the EPR signal of LiPc and suggests some technical solutions. It is most important to recognize that paramagnetic species such as LiPc present problems that are not commonly encountered in EPR spectroscopy.

India ink: a potential clinically applicable EPR oximetry probe

Using a material that already is in widespread use in humans, India ink, the first EPR measurements in a human have been made, using the India ink in a pre-existing tattoo. The EPR spectra of India ink are very sensitive to the partial pressure of oxygen (pO2), thereby making it feasible to use this approach to measure pO2 in tissues in patients. This potentially provides a means to measure this parameter directly with a sensitivity, accuracy, and repeatability that have not been available previously, and thereby to be able to individualize and guide treatment of diseases such as cancer and peripheral vascular insufficiency.

Simultaneous multi-site EPR spectroscopy in vivo

A gradient technique to measure electron paramagnetic resonance spectra simultaneously at several different locations is described. The technique is based on the use of point probes containing paramagnetic centers. The value of the magnetic field gradient is chosen to be sufficient to separate the EPR signals from the different paramagnetic probes yet at the same time small enough to change only minimally the shape of individual signals. The conditions to apply this technique are considered in detail. When experimental data have a high signal-to-noise ratio, the lineshape distortion induced by the gradient can be corrected with the aid of a known distribution function of paramagnetic centers within the probe. The maximum entropy deconvolution algorithm is successfully applied for the correction of significantly distorted lines. The technique is experimentally tested and applied to measure the concentration of oxygen in hypertrophied rat myocardium and normal rat kidney in vivo by low frequency EPR (L-band, 1.2 GHz). Two types of EPR oxygen-sensitive probes--lithium phthalocyanine crystals and synthetic carbohydrate chars--were used.

Lithium phthalocyanine: a probe for electron paramagnetic resonance oximetry in viable biological systems

Lithium phthalocyanine (LiPc) is a prototype of another generation of synthetic, metallic-organic, paramagnetic crystallites that appear very useful for in vitro and in vivo electron paramagnetic resonance oximetry. The peak-to-peak line width of the electron paramagnetic resonance spectrum of LiPc is a linear function of the partial pressure of oxygen (pO2); this linear relation is independent of the medium surrounding the LiPc. It has an extremely exchange-narrowed spectrum (peak-to-peak line width = 14 mG in the absence of O2). Physicochemically LiPc is very stable; its response to pO2 does not change with conditions and environments (e.g., pH, temperature, redox conditions) likely to occur in viable biological systems. These characteristics provide the sensitivity, accuracy, and range to measure physiologically and pathologically pertinent O2 tensions (0.1-50 mmHg; 1 mmHg = 133 Pa). The application of LiPc in biological systems is demonstrated in measurements of pO2 in vivo in the heart, brain, and kidney of rats.

Human startle reflex: technique and criteria for abnormal response

Because quantitative norms for the normal audiogenic startle response to repeated stimuli have not been previously reported, we now describe a technique for eliciting the startle response and analysing its habituation with repeated stimuli. We used binaural 105 dB tones delivered in 5 blocks of 4 tones. Successive blocks were separated by a 5 min period without tones stimuli and had progressively shorter inter-stimulus intervals (ISIs) beginning with 5 min in the first block and reducing to 1 min in the final, fifth block. We contrast the response and its habituation in a group of 8 normal subjects with that in a patient with clinically exaggerated startle. Based on the differences observed, we propose that the following criteria may be used to ascertain an abnormally increased startle response: (1) excessive duration of the myogenic response; (2) persistence of extracranial responses after the initial two blocks of stimuli; and (3) reduced habituation of the response (as measured by decreases in response duration and in the area under the curve of rectified EMG for the orbicularis oculi myogenic response). Our patient was abnormal on each of these measures. This result is consistent with past qualitative reports which have indicated that abnormal startle is associated both with excessive startle and with subnormal habituation. Study of further patients with hyperekplexia will be necessary to either confirm our data or modify our proposed criteria.

Blood clearance of dextran magnetite particles determined by a noninvasive in vivo ESR method

Dextran magnetite (DM) is a potential MR contrast agent with superparamagnetic properties. Its fast clearance from the blood and selective uptake by tissue macrophages provide advantages for imaging tumors in the liver and spleen. DM consists of a suspension of solid particles with a wide distribution of sizes. In this study we have used ESR spectroscopy to determine the blood clearance of DM injected iv in mice. The spectra are obtained on living animals by inserting the tail of a mice into the waveguide cavity of the ESR spectrometer and recording the ESR spectrum continuously. This procedure allows the direct measurement of the plasma clearance of DM from individual animals, without blood sampling. We applied this method to study the clearance of suspensions of DM particles with different average sizes.

Measurements of pertinent concentrations of oxygen in vivo

A new method able to measure the concentration of oxygen in complex biological systems, including in vivo, has been developed using low-frequency EPR and newly characterized free radicals that are very sensitive to the concentration of oxygen. The free radicals (fusinite and lithium phthalocyanine) are very stable in tissues (for at least 150 days), apparently nontoxic, and can reflect oxygen concentrations that are less than the Km of cytochrome oxidase (0.1 microM or lower). Their biological stability is indicated by the fact that repeated measurements with fusinite of the concentration of oxygen in skeletal muscle have been made in the same animal for more than 150 days without any change in sensitivity or signs of toxicity.

Is there a third photoreceptor involved in the control of chloroplast movements in mougeotia?

The photometric method was used to test a possibility proposed recently that a new photoreceptor with maximum activity at 620 nm is involved in mediating chloroplast rotation in Mougeotia (Z Lechowski, J Bialczyk [1988] Plant Physiol 88: 189-193). The hypothesis was tested under conditions of continuous dichromatic unilateral or mutually perpendicular irradiation with red light of wavelengths 620 or 660 (680) nanometers and far-red. When the red light was polarized parallel to the long cell axis, chloroplast response could be monitored by changing the direction of far-red irradiation. The level of the response obtained with red and far-red applied from the same direction depended on far-red intensity: at higher fluence rates the maximum response was shifted to longer wavelengths of red light. A high fluence rate of far-red inhibited the response. The absorption coefficients of Mougeotia chloroplasts were measured for the studied wave-lengths using the microphotometric method. Possible impact of absorption by the chloroplast on photoreception has been discussed. Current and previous results can be interpreted in terms of phytochrome action and do not support the involvement of the hypothetical 620 nanometer photoreceptor.

Measurement of time-resolved oxygen concentration changes in photosynthetic systems by nitroxide-based EPR oximetry

The application of recent developments of EPR oximetry to photosynthetic systems is described and used to study rapid processes in isolated thylakoid membranes from spinach and in intact photoautotrophic soybean cells. Using the peak heights of 15N perdeuterated Tempone and two microwave power levels oxygen evolution and consumption were measured. The method measured time-resolved oxygen concentration changes in the micromolar range. Oxygen evolution was linearly proportionate to the chlorophyl concentration of thylakoid membrane over the range studied (0-2 mg/ml). Oxygen evolution associated with single turnover light pulses was consistent with the four state model. The time (t1/2) to reach equilibrium of oxygen concentrations after a single turnover pulse was 0.4-0.5 ms, indicating that the evolution of oxygen coupled to the S4-S0 transition may be shorter than reported previously. The time for equilibrium of oxygen after single turnover pulses in soybean cells was relatively long (400 ms), which suggests that there are significant barriers to the free diffusion of oxygen in this system. The method also was used to study oxygen consumption by the electron transport chain of photosystem I and photosystem II. We conclude that EPR oximetry can provide quantitative and time-resolved data on oxygen concentrations with a sensitivity that is useful for studies of such systems.

Electron spin resonance microscopy of an in vitro tumour model

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A prospective study on sudden unexpected death in epilepsy

Sudden unexpected death accounts for a substantial portion of deaths among epileptics. The incidence of this phenomenon is probably 1 in 370 to 1 in 1,110 in the general epileptic population but may be even higher in the 20- to 40-year age group, and still higher if epileptics with symptomatic epilepsy are selected. Sudden unexpected death in epileptics has been observed at least once weekly by the Office of the Medical Examiner of Cook County (Chicago), Illinois, for many years. A year-long prospective study revealed that victims of this complication of epilepsy are most commonly black males averaging 35 years of age who have infrequent generalized seizures and usually have some structural lesion in the brain responsible for their seizures. They tend to abuse alcohol and have poor compliance with anticonvulsant medication. The electroencephalograms display considerable variability from record to record. At autopsy the heart, lung, and liver weights were heavier and the brain weights were lighter than expected. The mechanisms involved in sudden unexpected death in epileptics may include autonomically mediated cardiac arrhythmia alone or in combination with sudden "neurogenic" pulmonary edema and "backward" cardiac failure.

In vivo localized ESR spectroscopy reflecting metabolism

Localized electron spin resonance spectroscopy in live mice was performed using a surface coil operating at 1.1 GHz with sufficient sensitivity and stability to measure quantitatively the time course of the distribution, uptake, and reduction of nitroxides in selected organs/regions (liver, bladder, head) of mice. The ability to measure regional concentrations of nitroxides in vivo could be used for pharmacokinetic analysis of drugs labeled with nitroxides and for measurement of oxygen concentrations and redox metabolism.

Electron spin resonance imaging of tissues with lipid-rich areas

Electron spin resonance imaging and spectroscopy of lipid-rich samples were studied at 9 Ghz. Using both lipid- and aqueous-soluble nitroxides good delineation of fat- and muscle-rich regions of tissue was obtained. Several different principles can be used to differentiate between these types of tissues and potentially between different types of lipids. These principles include lipophilicity of nitroxides, viscosity (which is higher in lipids), oxygen solubility (oxygen is four times more soluble in lipids), and the distribution of paramagnetic metal ions. These techniques have potential applicability for directly studying metabolism and oxygen concentration in tissues by ESR techniques and for investigating potential contrast agents for in vivo NMR techniques.

Blue-light-induced chloroplast orientation in Mougeotia. Evidence for a separate sensor pigment besides phytochrome

Chloroplast orientation in the green alga Mougeotia has been induced by unidirectional red or blue light, given continuously during one hour. In addition, part of the preparations obtained scattered strong far-red light simultaneously with the orienting light. This far-red light completely abolished the response to red light, consistent with phytochrome as the sensor pigment for orientation in Mougeotia. In blue light, however, the response was completely insensitive to far-red light, thus pointing to a different sensor pigment in the shortwavelength region.

Chloroplast translocations in Lemna trisulca L. induced by continuous irradiation and by light pulses : Kinetic analysis

The analytical model describing the steady state position of chloroplasts in dependence of fluence rate as well as the chloroplast response to single strong light pulses has been proposed. The model is based on the following assumptions: 1. Irradiation of the cell generates the state X in the cell membrane region, proportional to the local fluence rate. After switching on the light, the value of X increases exponentially with the time constant of about 3 min. The dark decay of X is also exponential with the same time constant. The level of X controls all kinds of chloroplast arrangements. 2. The state X generates two further states: Y 1 and Y 2, the first of them representing attraction forces for chloroplasts and the second representing repulsion forces. Empirical equations have been found for both Y states. The fluence rate response curve can be described with the use of functions Y 1 and Y 2. 3. The kinetic analysis requires the introduction of two additional functions Z in order to account for delays and time dispersion of the chloroplast movement in response to driving and resistance factors. The computer program for the proposed model was developed and the results of calculations were compared with experimental data (fluence rate response curve and pulse effects) with satisfactory agreement. Initially no attempt was made to ascribe any physical meaning to the postulated states. Some suggestions in this respect are mentioned in the discussion.

Chloroplast translocations induced by light pulses : Effects of single light pulses

The effect of single blue-light pulses on chloroplast rearrangement was studied in the leaves of Tradescantia albiflora, Chlorophytum elatum, and Lemna trisulca. For measuring translocations in terrestrial plants the method of transmission changes was used; translocations in the water plant Lemna were studied by direct microscopic observation and counting. Strong light (30 W m(-2)) applied in the form of short pulses, shorter than a lag period of translocations, induces some transient effects in the following dark period. With short pulses, transient rearrangements of chloroplasts to a weak-light position were found. With longer pulse duration, biphasic responses took place in Tradescantia and Lemna: The initial movement to a partial strong-light position was followed by a wave of translocation to a weak-light arrangement. In Chlorophytum this type of response appeared only in a narrow fluence range. The validity of the reciprocity law in relation to fluence rate and time of irradiation was confirmed for Tradescantia. The results may give us an insight into the kinetics of the primary effects of light in the translocation process.