The characterization of materials by the inherently insensitive method of NMR spectroscopy plays a vital role in chemistry. Increasingly, hyperpolarization is being used to address the sensitivity limitation. Here, by reference to quinoline, we illustrate that the SABRE hyperpolarization technique, which uses para-hydrogen as the source of polarization, enables the rapid completion of a range of NMR measurements. These include the collection of (13)C, (13)C{(1)H}, and NOE data in addition to more complex 2D COSY, ultrafast 2D COSY and 2D HMBC spectra. The observations are made possible by the use of a flow probe and external sample preparation cell to re-hyperpolarize the substrate between transients, allowing repeat measurements to be made within seconds. The potential benefit of the combination of SABRE and 2D NMR methods for rapid characterization of low-concentration analytes is therefore established.

Many low-cost pulse oximeters sold to consumers demonstrate highly inaccurate readings. Unexpectedly, the accuracy of some low-cost pulse oximeters tested here performed similarly to more expensive, ISO-cleared units when measuring hypoxia in healthy subjects. None of those tested here met World Federation of Societies of Anaesthesiologists standards, and the ideal testing conditions do not necessarily translate these findings to the clinical setting. Nonetheless, further development of accurate, low-cost oximeters for use in clinical practice is feasible and, if pursued, could improve access to safe care, especially in low-income countries.

Arachidonyl trifluoromethyl ketone (AACOCF3) is a slow- and tight-binding inhibitor of the human cytosolic phospholipase A2 (cPLA2) [Street et al. (1993) Biochemistry 32, 5935]. 19F and 13C NMR experiments have been carried out to elucidate the structure of the cPLA2.AACOCF3 complex. One mole of AACOCF3 per mole of enzyme is tightly bound in the active site while excess molar equivalents of the inhibitor associate loosely and nonspecifically with hydrophobic regions of the protein. Incubation of the cPLA2.AACOCF3 complex with a 10-fold molar excess of a structurally related inhibitor allows the slow dissociation of the enzyme-inhibitor complex to be followed with 19F NMR. These results establish that the bound inhibitor is in slow exchange with the free ligand and that inhibition of the cPLA2 by AACOCF3 is not due to irreversible modification of the protein. AACOCF3 labeled with 13C at the carbonyl position was used to determine the nature of the bound inhibitor species. A comparison of the 13C NMR chemical shift value obtained from labeled enzyme-inhibitor complex (delta c 101.0 ppm) with the chemical shift values obtained from model compounds suggests that the enzyme-bound inhibitor species is a charged hemiketal. These results are very similar to those obtained previously with alpha-chymotrypsin and a peptidyl trifluoromethyl ketone inhibitor [Liang, T.-C., & Abeles, R. H. (1987) Biochemistry 26, 7603] and, by analogy with the serine proteases, a structural model for the cPLA2.AACOCF3 complex is proposed.

Correction of a very high grade carotid stenosis by endarterectomy in a normotensive man was followed by the development of severe unilateral head, eye, and face pain, seizures, and on the 6th day a fatal intracerebral hemorrhage. Autopsy revealed changes in the cerebral hemisphere ipsilateral to the endarterectomy that resembled the changes seen in malignant hypertension, whereas the opposite hemisphere was normal. These changes included hypercellularity and edema of arterial and arteriolar walls, with necrosis, extravasation of erythrocytes, and exudation of fibrin. We propose that the clinical and pathological features in this case were due to relative hyperperfusion of a cerebral hemisphere in which autoregulation had been impaired because of preoperative chronic hypoperfusion with chronic maximal dilatation of its blood vessels. This state of relative hyperperfusion is probably similar to the normal perfusion pressure breakthrough that occasionally occurs after the resection of cerebral arteriovenous malformations. It is similar to the breakthrough perfusion that occurs in severely hypertensive patients and results in hypertensive encephalopathy.

Maintenance treatment with infliximab improves BMD in patients with CD and this effect is independent of corticosteroid administration. The BMD response after infliximab suggests that TNF-alpha plays a role in the bone loss associated with CD.

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Background Pulse oximeter performance is degraded by motion artifacts and low perfusion. Manufacturers developed algorithms to improve instrument performance during these challenges. There have been no independent comparisons of these devices. Methods We evaluated the performance of four pulse oximeters (Masimo Radical-7, USA; Nihon Kohden OxyPal Neo, Japan; Nellcor N-600, USA; and Philips Intellivue MP5, USA) in 10 healthy adult volunteers. Three motions were evaluated: tapping, pseudorandom, and volunteer-generated rubbing, adjusted to produce photoplethsmogram disturbance similar to arterial pulsation amplitude. During motion, inspired gases were adjusted to achieve stable target plateaus of arterial oxygen saturation (SaO2) at 75%, 88%, and 100%. Pulse oximeter readings were compared with simultaneous arterial blood samples to calculate bias (oxygen saturation measured by pulse oximetry [SpO2] − SaO2), mean, SD, 95% limits of agreement, and root mean square error. Receiver operating characteristic curves were determined to detect mild (SaO2 < 90%) and severe (SaO2 < 80%) hypoxemia. Results Pulse oximeter readings corresponding to 190 blood samples were analyzed. All oximeters detected hypoxia but motion and low perfusion degraded performance. Three of four oximeters (Masimo, Nellcor, and Philips) had root mean square error greater than 3% for SaO2 70 to 100% during any motion, compared to a root mean square error of 1.8% for the stationary control. A low perfusion index increased error. Conclusions All oximeters detected hypoxemia during motion and low-perfusion conditions, but motion impaired performance at all ranges, with less accuracy at lower SaO2. Lower perfusion degraded performance in all but the Nihon Kohden instrument. We conclude that different types of pulse oximeters can be similarly effective in preserving sensitivity to clinically relevant hypoxia.

A simple, cheap and flexible flowcell based on a standard 5 mm NMR tube, designed for the monitoring of reactions but of wide applicability, is described. No modification of the NMR instrument is needed, allowing the system to be employed with any conventional NMR probe and magnet. The system is robust and economical in use of reagents, and can be used for studying both homogeneous and heterogeneous reactions.