Reduction by naloxone of lipopolysaccharide-induced neurotoxicity in mouse cortical neuron-glia co-cultures.

An inflammatory response in the CNS mediated by activation of microglia is a key event in the early stages of the development of neurodegenerative diseases. Using mouse cortical mixed glia cultures, we have previously demonstrated that the bacterial endotoxin lipopolysaccharide induces the activation of microglia and the production of proinflammatory factors. Naloxone, an opioid receptor antagonist, inhibits the lipopolysaccharide-induced activation of microglia and the production of proinflammatory factors. Using neuron-glia co-cultures, we extended our study to determine if naloxone has a neuroprotective effect against lipopolysaccharide-induced neuronal damage and analysed the underlying mechanism of action for its potential neuroprotective effect. Pretreatment of cultures with naloxone (1 microM) followed by treatment with lipopolysaccharide significantly inhibited the lipopolysaccharide-induced production of nitric oxide and the release of tumor necrosis factor-alpha, and significantly reduced the lipopolysaccharide-induced damage to neurons. More importantly, both naloxone and its opioid-receptor ineffective enantiomer (+)-naloxone were equally effective in inhibiting the lipopolysaccharide-induced generation of proinflammatory factors and the activation of microglia, as well as in the protection of neurons. These results indicate that the neuroprotective effect of naloxone is mediated by its inhibition of microglial activity and may be unrelated to its binding to the classical opioid receptors.

Studies on an immunologically induced synovitis model in pigs and sheep.

Chronic synovitis was induced in seven sheep and nine pigs to investigate the potential applicability of laser treatment in arthroscopic synovectomy. Systemic sensitization was accomplished using chicken egg or turkey egg albumin antigens with Freund's incomplete adjuvant, enriched with killed and dried Mycobacterium tuberculosis. Ten days after the second immunizing dose, skin sensitization testing was undertaken. After a satisfactory systemic reaction had been observed, the respective antigen was injected once or twice into the left knee of each animal at 2-week intervals. After chicken egg albumin sensitization at varying systemic immunization and joint injection doses, sheep (five of five) showed neither strong morphologic nor continuous synovitis, despite a positive systemic reaction. In pigs (three of three) the inflammatory signs also were unsatisfactory for the manifestation and characterization of a synovitis model. In contrast, the application of turkey egg albumin to pigs (six of six) during the 4-month study provided a persistent, clearly manifested synovitis that developed visible villi formation and an amber to gray synovial fluid and microscopically showed follicular aggregations of lymphocytes and plasma cells. In similarly immunized sheep (two of two), only a light synovitis developed with occasional perivascular inflammatory foci.

Synchronization in the human cardiorespiratory system.

We investigate synchronization between cardiovascular and respiratory systems in healthy humans under free-running conditions. For this aim we analyze nonstationary irregular bivariate data, namely, electrocardiograms and measurements of respiratory flow. We briefly discuss a statistical approach to synchronization in noisy and chaotic systems and illustrate it with numerical examples; effects of phase and frequency locking are considered. Next, we present and discuss methods suitable for the detection of hidden synchronous epochs from such data. The analysis of the experimental records reveals synchronous regimes of different orders n:m and transitions between them; the physiological significance of this finding is discussed.

One-dimensional, nonlinear determinism characterizes heart rate pattern during paced respiration.

This study focuses on the dynamic pattern of heart rate variability in the frequency range of respiration, the so-called respiratory sinus arrhythmia. Forty experimental time series of heart rate data from four healthy adult volunteers undergoing a paced respiration protocol were used as an empirical basis. For pacing-cycle lengths >8 s, the heartbeat intervals are shown to obey a rule that can be expressed by a one-dimensional circle map (next-angle map). Circle maps are introduced as a new type of model for time series analyses to characterize the nonlinear dynamic pattern underlying the respiratory sinus arrhythmia during voluntary paced respiration. Although these maps are not chaotic, the dynamic pattern shows typical imprints of nonlinearity. By starting from a piecewise linear model, which describes the different circle maps obtained from the empirical time series for various pacing frequencies, time invariant measures can be introduced that characterize the dynamic pattern of heart rate variability during voluntary slow-paced respiration.

[Comparison between continuous and intermittent thermodilution measurement of cardiac output during coronary artery bypass operation]. / Vergleich zwischen kontinuierlicher und intermittierender Thermodilutionsmessung des Herzzeitvolumens während koronarer Bypass-Operation.

PURPOSE OF THE STUDY: Continuous recording of cardiovascular parameters ranks high in cardioanaesthesia. Various methods to measure the cardiac output have been developed within a period of a few years. We compared the bolus thermodilution method (COI), which has been internationally adopted as "gold standard" method, with the continuous thermodilution method (CCO) for measuring the cardiac output by means of the CCO Vigilance Monitor. Our aim was to find out whether cardiac output can be determined with valid results during coronary artery bypass surgery when using CCO. METHOD: A flow-directed catheter was used (8 Fr. Intelli-Cath CCO PA) in 98 patients during coronary artery bypass surgery after initiation of anaesthesia, introducing the catheter via the right V.jugularis interna, for continuous measurement of the cardiac output via the CCO Vigilance Monitor. The same equipment was also used to measure the cardiac output via the bolus thermodilution method (COI mode) at the following stages: after abandoning the CCO mode 10 minutes subsequent to beginning the operation before sternotomy; 10 minutes after sternotomy before connecting to the heart-lung machine; 15 minutes after disconnecting the heart-lung machine before closing the thorax; and 10 minutes after closing the thorax. As a corresponding comparative value of the CCO method, we used the average cardiac output value calculated for each of the four times of measurement for the last three minutes before applying the boli. RESULTS: In regression analysis we chose the linear model CCO = b x COI with gradient b = 1 and zero point ordinate a = 0. The identity measures, Spearman's rank correlation coefficients, and linear regression coefficients calculated for the four times of measurement, showed good agreement. Scatter of the paired differences between both methods (CCO-CCI) did not have any deterministic structure at all times of measurement. The average bias at the 4 times of measurement was 0.10 l/min, -0.12 l/min, -0.1 l/min, and -0.03 l/min, respectively, with a precision = 2 x s of 1.17 l/min, 1.36 l/min, 1.69 l/min and 1.50 l/min, respectively. The average relative error (100 x [CCO-COI]/COI) with standard deviation was calculated for the 4 times of measurement as 3.2% (s = 15.4%), -1.6% (s = 15.3%), -0.9% (s = 13.9%) and -0.3% (s = 12.0%), respectively. CONCLUSIONS: Literature references show that the continuous thermodilution method is not only valid for intensive-care long-term measurement of cardiac output with approximately stationary haemodynamics, but also-as our results prove-valid if haemodynamics are not usually stationary, such as during coronary artery bypass surgery. The pros of the continuous thermodilution method are that no additional equipment is required apart from the standard equipment used in intensive-care medicine and cardio-anaesthesiology: that there is no stress caused by volume; and that manipulation is safe because no calibration routine is needed and also because measurement and analysis techniques are fully automated. Hence, we are of the opinion that the intraoperative use of this cardiac output measurement technique during open heart surgery is clinically indicated.

[Methodology in the analysis of asymmetry in fluctuations of heart rate]. / Methodik der Analyse der Asymmetrie in den Fluktuationen der Herzfrequenz.

Time series of R-R intervals show fluctuations which are neither symmetric regarding the changes in length of heart beats nor regarding the number of heart beats during the phases of heart rate acceleration and deceleration. These features of heart rate variability cannot be quantified by the analysis of the beat-to-beat variability or by the spectrum analysis of heart rate. The analysis of asymmetry using the distribution function of the differences between consecutive R-R intervals creates measures for the total, central, and peripheral asymmetry. These measures quantify different aspects of the shape of the distribution function. The asymmetry measures are either based on the amount of difference between consecutive R-R intervals or the number of lengthening R-R intervals in a sequence of heart beats. The analysis of asymmetry of R-R interval time series shows differences among test subjects during rest.

[Mathematical model of "respiratory sinus arrhythmia"]. / Mathematisches Modell der "respiratorischen Sinusarrhythmie".

We developed a mathematical model of "respiratory" sinus arrhythmia. The model combines a representation continuous in time of the parasympathetic and sympathetic innervation and the membrane potential of the pace maker cell of the heart with a beat-by-beat representation of the cardiovascular variables like diastolic and systolic blood pressure, pulse pressure, total peripheral resistance and baroreceptor activity. The influence of respiration is described separately by mechanical and central neural mechanisms. Using this nonlinear model of "respiratory" heart rate variability one is able to explore in a theoretical way the different heart rate variability generating mechanisms, either as isolated or combined effects on both, heart rate variability in the frequency range of respiration and in the frequency range around 0.1 Hz. By fitting a simulated RR interval time course to a physiological RR interval time course one can estimate the relative weight of the different mechanisms generating this physiological heart rate variability.

[Methodology for analysis of binary sequences in heart rate]. / Methodik der Analyse binärer Sequenzen in der Herzfrequenz.

A qualitative and quantitative method for the description of heart rate variability is demonstrated. It is based on a symbolic coding of time series taken from heartbeat intervals and calculation of the value "entropy" as a measure for information. Entropy seems to be a propriate measure to gain insight into the temporal structure underlying the phenomenon of heart variability.

Mimosine reversibly arrests cell cycle progression at the G1-S phase border.

It has previously been demonstrated that the compound mimosine inhibits cell cycle traverse in late G1 phase prior to the onset of DNA synthesis (Hoffman BD, Hanauske-Abel HM, Flint A, Lalande M: Cytometry 12:26-32, 1991; Lalande M: Exp Cell Res 186:332-339, 1990). These results were obtained by using flow cytometric analysis of DNA content to compare the effects of mimosine on cell cycle traverse with those of aphidicolin, an inhibitor of DNA polymerase alpha activity. We have now measured the incorporation of bromodeoxyuridine into lymphoblastoid cells by flow cytometry to determine precisely where the two inhibitors act relative to the initiation of DNA synthesis. It is demonstrated here that mimosine arrests cell cycle progression at the G1-S phase border. The onset of DNA replication occurs within 15 min of releasing the cells from the mimosine block. In contrast, treatment with aphidicolin results in the accumulation of cells in early S phase. These results indicate that mimosine is a suitable compound for affecting the synchronous release of cells from G1 into S phase and for analyzing the biochemical events associated with this cell cycle phase transition.

The effect of transportation stress on circulating corticosteroids, enzyme activities and hematological values in laboratory dogs.

Stress during transportation was monitored in truck-transported Beagle dogs "IVTK HD". Cortisol (F), corticosterone (B), red and white blood cell parameters, and enzyme activities in plasma were estimated. Plasma levels of cortisol and corticosterone were increased significantly during transportation and returned to basal values overnight post arrival. Hematocrit, hemoglobin, erythrocytes and leukocytes increased moderately. No obvious differences in enzyme activities were observed. Only alpha-HBDH values dropped significantly at the end of the 9.5 h transport period. This study confirms, although individual reaction is remarkably different, transportation as a potent stressor for Beagle dogs.

Integrative neurovegetative and motor control: phenomena and theory.

The general problem of specificity and the existence of separate central control systems for different peripheral systems is handled and exemplified by the control of circulation, respiration and motor innervation. The considerations are based on several earlier experimental studies of spontaneous coordinations of rhythmic activities in anaesthetized dogs and conscious men and microelectrode recordings and local cooling experiments in the brain stem of anaesthetized dogs and cats. Analysis of findings and logical deductions result in the statement that central control systems must be partly identical and that the usual criteria of labelling central neurones according to their coordination to specific control systems are necessary but not sufficient. Instead the picture of a multifunctional common network emerges forming the substrate of the observed common central rhythmicity. In this network specificity is a quantitative property of neurones. A simple model is outlined illustrating that slight inhomogeneity leads to graded input-output specificity in the network which changes with changing conditions. The degree of neuronal specificity increases in the direction of the outputs. Applications of the network model to concrete observations in animal experiments are discussed.

Effects of continuous infusions of 4-hydroxyoestradiol and oestradiol on plasma LH-levels in the ovariectomized ewe.

Ovariectomized ewes were infused over a period of 12 h at constant rates with different doses of the catecholoestrogen 4-hydroxyoestradiol (4-OHE2) or the primary oestrogen oestradiol (E2) via a catheter placed in the right atrium. Blood samples were drawn every hour for a total period of 48 h starting 1 h before the beginning of the steroid infusion. Luteinizing hormone (LH), 4-OHE2 and E2 concentrations were measured in these samples by specific radioimmunoassays. Infusions of low doses E2 (0.5 microgram/h) or 4-OHE2 (2 micrograms/h) caused only a suppression of LH-secretion. At doses of 1 microgram E2/h or 5 micrograms 4-OHE2/h this negative effect was followed by inconsistent elevations of plasma LH. Beyond this threshold dose, E2 at infusion rates of 2, 5 and 10 micrograms/h and 4-OHE2 at infusion rates of 10, 25 and 50 micrograms/h produced the negative effect and massive LH-surges. At still higher infusion rates (E2: 20 micrograms/h, 4-OHE2: 100 micrograms/h) lower elevations of plasma LH levels were observed. 4-OHE2 had to be infused at 4-5 times higher rates than E2 to obtain comparable plasma concentrations of either oestrogen. Under this condition the effects of 4-OHE2 and E2 were similar indicating that 4-OHE2 has the same potency as E2 at central target sites.