Pulsed EPR Study of the Initial Steps of Radical-Scavenging Reactions of C70 with Diphenylphosphine Oxide, Hydroxycyclohexyl, and 2-Hydroxypropyl Radicals.

The radical scavenging reactions of C70 were investigated using time-resolved (TR-) and pulsed electron paramagnetic resonance (EPR) methods. In the diphenylphosphine oxide (DPPO) radical and C70 system, structural isomers of the adduct radicals of C70 appeared in the TR-EPR spectrum with clear hyperfine structures due to the phosphorus atom. Four isomers were identified through the analysis of the hyperfine coupling constants. The assignment of the adduct radicals was confirmed by the semiempirical calculation of the relative addition reaction rate constants that produce each isomer. The radical scavenging rate constants, ksca, of C70 in toluene were determined for DPPO, hydroxylcyclohexyl, and 2-hydroxypropyl radicals through electron spin echo observations using the pulsed-EPR method. The ksca values were nearly 109 mol-1 dm3 s-1 and were almost equal to the diffusion-controlled rate constant in toluene. This proves that C70 acts as an excellent radical scavenger. In addition, the radical addition rate constants, kadd, of C70 for varying carbon atoms in C70 were obtained by considering the peak intensity ratio of the adduct radicals in the TR-EPR spectrum. In this study, we demonstrated that the large number of carbon atoms in pentagons (five-membered rings) is responsible for the high reactivity of fullerenes.

Assessment of Lower-limb Vascular Endothelial Function Based on Enclosed Zone Flow-mediated Dilation.

This paper proposes a novel non-invasive method for assessing the vascular endothelial function of lower-limb arteries based on the dilation rate of air-cuff plethysmograms measured using the oscillometric approach. The principle of evaluating vascular endothelial function involves flow-mediated dilation. In the study conducted, blood flow in the dorsal pedis artery was first monitored while lower-limb cuff pressure was applied using the proposed system. The results showed blood flow was interrupted when the level of pressure was at least 50 mmHg higher than the subject's lower-limb systolic arterial pressure and that blood flow velocity increased after cuff release. Next, values of the proposed index, %ezFMDL, for assessing the vascular endothelial function of lower-limb arteries were determined from 327 adult subjects: 87 healthy subjects, 150 subjects at high risk of arteriosclerosis and 90 patients with cardiovascular disease (CAD). The mean values and standard deviations calculated using %ezFMDL were 30.5 ± 12.0% for the healthy subjects, 23.6 ± 12.7% for subjects at high risk of arteriosclerosis and 14.5 ± 15.4% for patients with CAD. The %ezFMDL values for the subjects at high risk of arteriosclerosis and the patients with CAD were significantly lower than those for the healthy subjects (p < 0.01). The proposed method may have potential for clinical application.

Quantitative Evaluation of Pain during Electrocutaneous Stimulation using a Log-Linearized Peripheral Arterial Viscoelastic Model.

In clinical practice, subjective pain evaluations, e.g., the visual analogue scale and the numeric rating scale, are generally employed, but these are limited in terms of their ability to detect inaccurate reports, and are unsuitable for use in anesthetized patients or those with dementia. We focused on the peripheral sympathetic nerve activity that responds to pain, and propose a method for evaluating pain sensation, including intensity, sharpness, and dullness, using the arterial stiffness index. In the experiment, electrocardiogram, blood pressure, and photoplethysmograms were obtained, and an arterial viscoelastic model was applied to estimate arterial stiffness. The relationships among the stiffness index, self-reported pain sensation, and electrocutaneous stimuli were examined and modelled. The relationship between the stiffness index and pain sensation could be modelled using a sigmoid function with high determination coefficients, where R2 ≥ 0.88, p < 0.01 for intensity, R2 ≥ 0.89, p < 0.01 for sharpness, and R2 ≥ 0.84, p < 0.01 for dullness when the stimuli could appropriately evoke dull pain.

A new arterial mechanical property indicator reflecting differences in invasive stimulus intensity induced by alteration of remifentanil concentration during laryngoscopy.

BACKGROUND: Reliable analgesia monitoring is not available for general anaesthesia cases. In 2003, we introduced a method to characterise arterial mechanical properties, which we termed arterial stiffness (K). However, it is unclear whether differences in K actually indicate changes in the intensity of a noxious stimulus. Thus, we examined the relationship between stress intensity and the value of K. METHODS: Thirty patients under general anesthesia were randomly divided into two remifentanil concentration groups (2 and 6 ng/mL). After a steady concentration of remifentanil was achieved for at least 3 minutes, laryngoscopy was performed. After completion of laryngoscopy, once the K value returned to near-baseline, laryngoscopy with endotracheal intubation was performed, and the value of K after the procedure was recorded and analyzed. RESULTS: In total, data were obtained for 28 of 30 patients. The values of K before the laryngoscopy were not significantly different between the groups (2 ng/mL group: 13.1 [8.5-33.1] mmHg/%; 6 ng/mL group: 11.6 [4.3-31.4] mmHg/%; P=0.53). After laryngoscopy, K was approximately 2 times greater in the 2 ng/mL group than in the 6 ng/mL group (39.0 [13.6-115.9] mmHg/% vs. 19.0 [5.5-85.1] mmHg/%, P=0.02). After intubation also, K was approximately 2 times greater in the 2 ng/mL group (52.0 [27.7-122.0] mmHg/% vs. 24.3 [7.2-94.9] mmHg/%, P=0.04). CONCLUSIONS: The value for arterial stiffness (K) non-proportionally changes in response to stimulus intensity; therefore, it has the potential to be used as an indicator of nociceptive stimulation intensity.

Monitoring of peripheral vascular condition using a log-linearized arterial viscoelastic index during endoscopic thoracic sympathectomy.

This paper proposes a novel technique to support the monitoring of peripheral vascular conditions using biological signals such as electrocardiograms, arterial pressure values and pulse oximetry plethysmographic waveforms. In this approach, a second-order log-linearized model (referred to here as a log-linearized peripheral arterial viscoelastic model) is used to describe the non-linear viscoelastic relationship between blood pressure waveforms and photo-plethysmographic waveforms. The proposed index enables estimation of peripheral arterial wall stiffness changes induced by sympathetic nerve activity. The validity of the method is discussed here based on the results of peripheral vascular condition monitoring conducted during endoscopic thoracic sympathectomy (ETS). The results of ETS monitoring showed significant changes in stiffness variations between the periods before and during the procedures observed (p < 0.01) as well as during and after them (p < 0.01), so that it was confirmed that sympathetic nerve activity is drastically decreased in the area around the monitoring site after the thoracic sympathetic nerve trunk on the monitoring side is successfully blocked. In addition, no change was observed in the values of the proposed index during the ETS procedure on the side opposite that of the monitoring site. The experimental results obtained clearly show the proposed method can be used to assess changes in sympathetic nerve activity during ETS.