Contraction of smooth muscle cells is generally as-Although the importance of [Ca 2ϩ ] i and LC20 1 phosphorylation in the regulation of smooth muscle contraction is recognized, certain incongruous observations have indicated that additional factors may also regulate, particularly, sustained contractions of smooth muscle. During the initiation of smooth muscle contraction, a transient rise in [Ca 2ϩ

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The application of T 1 in the rotating frame (T 1 ) to functional MRI in humans was studied at 3 T. Increases in neural activity increased parenchymal T 1 . Modeling suggested that cerebral blood volume mediated this increase. A pulse sequence named spin-locked echo planar imaging (SLEPI) that produces both T 1 and T 2 * contrast was developed and used in a visual functional MRI (fMRI)experiment. Spin-locked contrast significantly augments the T 2 * blood oxygen level-dependent (BOLD) contrast in this sequence. The total functional contrast generated by the SLEPI sequence (1.31%) was 54% larger than the contrast (0.85%) obtained from a conventional gradient-echo EPI sequence using echo times of 30 ms. Analysis of image SNR revealed that the spin-locked preparation period of the sequence produced negligible signal loss from static dephasing effects. The SLEPI sequence appears to be an attractive alternative to conventional BOLD fMRI, particularly when long echo times are undesirable, such as when studying prefrontal cortex or ventral regions, where static susceptibility gradients often degrade T 2 *-weighted images. Magn Reson Med 54: 1155-1162, 2005.

The role of protein kinase C (PKC) isoforms in myogenic tone of the ferret coronary microcirculation was investigated by measuring fura 2 Ca(2+) signals, PKC immunoblots, contractile responses, and confocal microscopy of PKC translocation. Phorbol ester-evoked contractions were completely abolished in the absence of extracellular Ca(2+) but involved a Ca(2+) sensitization relative to KCl contractions. Immunoblotting using isoform-specific antibodies showed the presence of PKC-alpha and -iota and traces of PKC-epsilon and -mu in the ferret coronary microcirculation. PKC-beta was not detectable. When intraluminal pressure (40 to 60 and 80 mmHg) was increased, ferret coronary arterioles showed a transient increase in fura 2 Ca(2+) signals, whereas the myogenic tone remained sustained. The increase in Ca(2+) and tone was sustained at 100 mmHg. Isolated ferret coronary arterioles were fixed and immunostained for PKC-alpha at 40 and 100 mmHg intraluminal pressure. PKC translocation was determined by confocal microscopy. Increased PKC translocation was observed when vessels were exposed to 100 mmHg relative to that at resting pressure (40 mmHg). These results suggest a link between the Ca(2+) sensitization that occurs during the myogenic contraction and activation of the alpha-isoform of PKC.

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Summary The extent of neuromuscular blockade during anaesthesia is frequently measured using a train‐of‐four stimulus. Various monitors have been used to quantify the train‐of‐four, including mechanomyography, acceleromyography and electromyography. Mechanomyography is often considered to be the laboratory gold standard of measurement, but is not commercially available and has rarely been used in clinical practice. Acceleromyography is currently the most commonly used monitor in the clinical setting, whereas electromyography is not widely available. We compared a prototype electromyograph with a newly constructed mechanomyograph and a commercially available acceleromyograph monitor in 43 anesthetised patients. The mean difference (bias; 95% limits of agreement) in train‐of‐four ratios was 4.7 (−25.2 to 34.6) for mechanomyography vs. electromyography; 14.9 (−13.0 to 42.8) for acceleromyography vs. electromyography; and 9.8 (−31.8 to 51.3) for acceleromyography vs. mechanomyography. The mean difference (95% limits of agreement) in train‐of‐four ratios between opposite arms when using electromyography was −0.7 (−20.7 to 19.3). There were significantly more acceleromyography train‐of‐four values > 1.0 (23%) compared with electromyography or mechanomography (2–4%; p < 0.0001). Electromyography most closely resembled mechanomyographic assessment of neuromuscular blockade, whereas acceleromyography frequently produced train‐of‐four ratio values > 1.0, complicating the interpretation of acceleromyography results in the clinical setting.

Background: Train-of-four twitch monitoring can be performed using palpation of thumb movement, or by the use of a more objective quantitative monitor, such as mechanomyography, acceleromyography, or electromyography. The relative performance of palpation and quantitative monitoring for determination of the train-of-four ratio has been studied extensively, but the relative performance of palpation and quantitative monitors for counting train-of-four twitch responses has not been completely described. Methods: We compared train-of-four counts by palpation to mechanomyography, acceleromyography (Stimpod™), and electromyography (TwitchView Monitor™) in anaesthetised patients using 1691 pairs of measurements obtained from 46 subjects. Results: There was substantial agreement between palpation and electromyography (kappa ¼ 0.80), mechanomyography (kappa ¼ 0.67), or acceleromyography (kappa ¼ 0.63). Electromyography with TwitchView and mechanomyography most closely resembled palpation, whereas acceleromyography with StimPod often underestimated train-of-four count. With palpation as the comparator, acceleromyography was more likely to measure a lower train-of-four count, with 36% of counts less than palpation, and 3% more than palpation. For mechanomyography, 31% of train-of-four counts were greater than palpation, and 9% were less. For electromyography, 15% of train-of-four counts were greater than palpation, and 12% were less. The agreement between acceleromyography and electromyography was fair (kappa ¼ 0.38). For acceleromyography, 39% of train-of-four counts were less than electromyography, and 5% were more. Conclusions: Acceleromyography with the StimPod frequently underestimated train-of-four count in comparison with electromyography with TwitchView.

Purpose: To develop a novel pulse sequence called spinlocked echo planar imaging (EPI), or (SLEPI), to perform rapid T 1 -weighted MRI. Materials and Methods:SLEPI images were used to calculate T 1 maps in two healthy volunteers imaged on a 1.5-T Sonata Siemens MRI scanner. The head and extremity coils were used for imaging the brain and blood in the popliteal artery, respectively.Results: SLEPI-measured T 1 was 83 msec and 103 msec in white (WM) and gray matter (GM), respectively, 584 msec in cerebrospinal fluid (CSF), and was similar to values obtained with the less time-efficient sequence based on a turbo spin-echo readout. T 1 was 183 msec in arterial blood at a spin-lock (SL) amplitude of 500 Hz. Conclusion:We demonstrate the feasibility of the SLEPI pulse sequence to perform rapid T 1 MRI. The sequence produced images of higher quality than a gradient-echo EPI sequence for the same contrast evolution times. We also discuss applications and limitations of the pulse sequence. T 1⌹ OR "SPIN-LOCKED" MRI produces contrast unlike conventional T 1 -or T 2 -weighted images. Spin-locking is achieved by the application of a low power on-resonance radiofrequency (RF) pulse to the magnetization in the transverse plane. The resulting MR signal decays with a time constant T 1 and is dominated by processes that occur with a correlation time, c , that is related to the amplitude of the spin-lock (SL) pulse (␥B 1 /2 ), which typically ranges from zero to a few kilohertz. T 1 is commonly referred to as the longitudinal relaxation time constant in the rotating frame. In biological tissues, T 1 increases with higher B 1 and approaches T 2 , the spin-spin relaxation time constant, as the amplitude of the SL pulse is reduced to zero. The sensitivity of T 1 to low-frequency interactions facilitates the study of biological tissues in a manner that is unattainable by conventional T 1 -and T 2 -based MR methods. Consequently, T 1 MRI has been used to investigate a variety of tissues such as breast, brain, and cartilage (1-3).Recently, T 1 imaging has been employed to measure blood flow and oxygen metabolism and the effect of tracers such as H 2 17 O (4,5). These studies were performed using standard spin-echo, turbo (fast) spinecho, or gradient-echo-based pulse sequences. There is substantial evidence demonstrating that the T 1 relaxation time parameter is sensitive to the early detection of cerebral ischemia (6 -8). Kettunen et al (9) revealed a linear dependence of T 1 as a function of oxygen saturation in experiments performed in vitro. Dynamic studies such as these and others that involve imaging of flowing spins such as that of blood would benefit from a fast T 1 imaging technique that is able to acquire images in the order of tens of milliseconds.A method of rapid image acquisition is the echo planar imaging (EPI) technique (10,11). In its conventional form, the EPI pulse sequence consists of an excitation pulse that is followed by a train of gradientechoes within a single pulse repetition time (TR), and is capable of generat...