Electron Spin Resonance Study of Nitroxide Radical Adsorption at Cupric Ions in the Metal−Organic Framework Compound Cu₃(btc)₂

The Cu(II) pairs in the paddle-wheel building blocks of the metal−organic framework compound Cu₃(btc)₂ give rise to an antiferromagnetic spin state with an electron spin resonance (ESR)-silent <i>S</i> = 0 ground state. However, the adsorption of di-<i>tert</i>-butyl nitroxide (DTBN) radicals leads to the formation of an unusual nitroxide ESR spectrum and later, upon thermal treatment of the samples, to distinct paramagnetic Cu(II) centers, whose ESR signals can be observed at temperatures below 70 K. Various scenarios for the suppression of the antiferromagnetic coupling of the Cu(II) ions in the paddle-wheel units by interaction with the nitroxide and the subsequent formation of these <i>S</i> = 1/2 copper centers are discussed

Image_1_Increased Default Mode Network Connectivity in Obsessive–Compulsive Disorder During Reward Processing.JPEG

<p>Objective: Obsessive-compulsive disorder (OCD) is characterized by anxiety-provoking, obsessive thoughts (i.e., obsessions) which patients react to with compulsive behaviors (i.e., compulsions). Due to the transient feeling of relief following the reduction of obsession-induced anxiety, compulsions are often described as relieving or even rewarding. Several studies investigated functional activation during reward processing in OCD, but findings are heterogeneous up to now and little is known about potential alterations in functional connectivity.</p><p>Method: Against this background we studied OCD patients (n = 44) and healthy controls (n = 37) during the receipt of monetary reward by assessing both activation and functional connectivity.</p><p>Results: Patients showed a decreased activation in several frontal regions and the posterior cingulate (PCC, BA31) together with a stronger connectivity between the PCC and the vmPFC (BA10).</p><p>Conclusion: Present findings demonstrate an increased connectivity in patients within major nodes of the default mode network (DMN)—a network known to be involved in the evaluation of internal mental states. These results may indicate an increased activity of internal, self-related processing at the expense of a normal responsiveness toward external rewards and incentives. This, in turn, may explain the constant urge for additional reinforcement and patients' inability to inhibit their compulsive behaviors.</p

Image_2_Increased Default Mode Network Connectivity in Obsessive–Compulsive Disorder During Reward Processing.JPEG

<p>Objective: Obsessive-compulsive disorder (OCD) is characterized by anxiety-provoking, obsessive thoughts (i.e., obsessions) which patients react to with compulsive behaviors (i.e., compulsions). Due to the transient feeling of relief following the reduction of obsession-induced anxiety, compulsions are often described as relieving or even rewarding. Several studies investigated functional activation during reward processing in OCD, but findings are heterogeneous up to now and little is known about potential alterations in functional connectivity.</p><p>Method: Against this background we studied OCD patients (n = 44) and healthy controls (n = 37) during the receipt of monetary reward by assessing both activation and functional connectivity.</p><p>Results: Patients showed a decreased activation in several frontal regions and the posterior cingulate (PCC, BA31) together with a stronger connectivity between the PCC and the vmPFC (BA10).</p><p>Conclusion: Present findings demonstrate an increased connectivity in patients within major nodes of the default mode network (DMN)—a network known to be involved in the evaluation of internal mental states. These results may indicate an increased activity of internal, self-related processing at the expense of a normal responsiveness toward external rewards and incentives. This, in turn, may explain the constant urge for additional reinforcement and patients' inability to inhibit their compulsive behaviors.</p

Interaction analyses of heart rate and respiration are shown.

<p>Increased uncoupling between heart rate and respiratory rate is shown in patients in comparison to controls and relatives. Both measures, cross conditional entropy (A) and shannon entropy of joint symbolic dynamics (B) provide a quantification of the degree of coupling between both signals. Boxes indicate data between the 25th and 75th percentile with the horizontal bar reflecting the median (□ = mean; - = 1st and 99th percentile; x = minimum and maximum of data). Significant differences of Bonferoni corrected pair-wise comparisons are indicated: ** p<.01; *** p<.001.</p

Clinical and demographic data of participants.

<p>PANSS - Positive and negative syndrome; scale; SANS - Scale for the assessment of negative symptoms; SAPS - Scale for the assessment of positive symptoms; n.a. – not applicable.</p

Obtained parameters of experiment 1 and 2 (not included in figures).

<p>Values are displayed as mean ± standard deviation, RMSSD_Resp = root mean square of successive differences, Resp = respiratory rate, HRV = heart rate variability, TV = tidal volume, HF high frequency, LF = low frequency, Minute Vent = minute ventilation; Tidal Vol = tidal volume, SpO₂ = blood oxygen saturation level, ratio I/E = inspiratory to expiratory time ratio, MF = mid frequency, Hc = compression entropy, CCE = cross conditional entropy, n.s. = not significant, n.d. = not done (ANOVA not significant).</p

The figure indicates parameters of HRV in patients, relatives and controls.

<p>Increased mean heart rates of patients and relatives are depicted in A. Decreased parasympathetic modulation is shown in B by means of the RMSSD and in C using the high frequency band of heart rate. Reduced complexity is shown for patients and relatives in D. Respiratory sinus arrhythmia (E) indicates low cardiac vagal modulation in patients and relatives. Transfer function (F) shows that decreased cardiac vagal modulation in patients and relatives is independent from the respiratory rate. Boxes indicate data between the 25th and 75th percentile with the horizontal bar reflecting the median (□ = mean; - = 1st and 99th percentile; x = minimum and maximum of data). Significant differences of Bonferoni corrected pair-wise comparisons are indicated: * p<.05; ** p<.01; *** p<.001.</p

Representative parameters of respiration and heart rate are shown before, during and after a stress task.

<p>Healthy controls are characterized by an increased heart rate (A) and respiratory rate during the stress task. Cardiac vagal modulation as shown by RSA (C) is decreased while some evidence was found for increased uncoupling of heart rate and breathing rate during the task (D). Boxes indicate data between the 25th and 75th percentile with the horizontal bar reflecting the median (□ = mean; - = 1st and 99th percentile; x = minimum and maximum of data). Significant differences of Bonferoni corrected pair-wise comparisons are indicated: (*) p = .05; ** p<.01; *** p<.001.</p

Parameters of respiratory analysis of controls, patients and relatives are presented.

<p>The pattern of significantly altered values of patients in comparison to controls is represented in A–F. The increased breathing rate of patients is presented in A. As shown in B, the inspiratory-to-expiratory time ratio is increased in patients indicating a reduction of the exhalation time. Patients breathe shallowly as indicated in C. Most pronounced are increased frequency bands of respiration as indicated in D–F. Boxes indicate data between the 25th and 75th percentile with the horizontal bar reflecting the median (□ = mean; - = 1st and 99th percentile; x = minimum and maximum of data). Significant differences of Bonferoni corrected pair-wise comparisons are indicated: * p<.05; ** p<.01; *** p<.001.</p