OBJECTIVE Ultrasound can be precisely focused through the intact human skull to target deep regions of the brain for stereotactic ablations. Acoustic energy at much lower intensities is capable of both exciting and inhibiting neural tissues without causing tissue heating or damage. The objective of this study was to demonstrate the effects of low-intensity focused ultrasound (LIFU) for neuromodulation and selective mapping in the thalamus of a large-brain animal. METHODS Ten Yorkshire swine ( Sus scrofa domesticus) were used in this study. In the first neuromodulation experiment, the lemniscal sensory thalamus was stereotactically targeted with LIFU, and somatosensory evoked potentials (SSEPs) were monitored. In a second mapping experiment, the ventromedial and ventroposterolateral sensory thalamic nuclei were alternately targeted with LIFU, while both trigeminal and tibial evoked SSEPs were recorded. Temperature at the acoustic focus was assessed using MR thermography. At the end of the experiments, all tissues were assessed histologically for damage. RESULTS LIFU targeted to the ventroposterolateral thalamic nucleus suppressed SSEP amplitude to 71.6% ± 11.4% (mean ± SD) compared with baseline recordings. Second, we found a similar degree of inhibition with a high spatial resolution (∼ 2 mm) since adjacent thalamic nuclei could be selectively inhibited. The ventromedial thalamic nucleus could be inhibited without affecting the ventrolateral nucleus. During MR thermography imaging, there was no observed tissue heating during LIFU sonications and no histological evidence of tissue damage. CONCLUSIONS These results suggest that LIFU can be safely used to modulate neuronal circuits in the central nervous system and that noninvasive brain mapping with focused ultrasound may be feasible in humans.
We have studied the effects of clinically useful anthraquinones on the cardiac sarcoplasmic reticulum calcium-release channel. (Circulaion Research 1990;67:272-283) Anthraquinones are highly effective chemotherapeutic agents with a wide spectrum of antitumor activity. Their clinical use is limited principally by a dose-dependent cardiotoxicity, which is produced both by anthracyclines' (e.g., doxorubicin, epirubicin, and idarubicin) and by anthracenediones2 (e.g., mitoxantrone), although the histological features produced by each group are reported to show significant differences.3 Among the anthracyclines, epirubicin and idarubicin are less cardiotoxic than doxorubicin.4 The subcellular effects of doxorubicin in the heart have been extensively investigated,5 but the mechanism of cardiotoxicity remains unclear.Doxorubicin can undergo a reduction reaction to a semiquinone species that is a potential generator of oxygen-derived free radicals.6 It has been proposed that this might initiate generalized membrane system disruption through lipid peroxidation,7 leading to intracellular calcium overload. Abnormalities of the sarcoplasmic reticulum (SR) are characteristic early
The properties of calcium-release channels of sheep cardiac muscle junctional sarcoplasmic reticulum (SR), have been investigated under voltage-clamp conditions following the fusion of isolated membrane vesicles with planar phospholipid bilayers. In the presence of activating calcium on the cytosolic side of the membrane, additions of the benzimidazole derivative sulmazole (AR-L 115BS) increased the open probability (Po) of the channel reaching saturating values of 1.0 at 3 mM sulmazole. The drug did not affect single-channel conductance and activation was readily reversible. Analysis of channel open and closed lifetimes suggested that low concentrations of sulmazole (0.1 mM) may sensitize the channel to activating calcium, while at higher concentrations (1 mM and above), calcium and sulmazole act synergistically to produce a unique gating scheme for the channel. Millimolar concentrations of sulmazole also stimulate a degree of channel opening at subactivating (60 pM) calcium concentrations. Openings occurring under these conditions show very different kinetics to those of the calcium-activated channel but have an identical single-channel conductance and are modified by ATP, magnesium, ruthenium red and ryanodine in a similar manner to the calcium-activated channel. The release of calcium from the SR following the activation of the calcium-release channel by sulmazole may contribute to the positive inotropic action of this drug on mammalian cardiac muscle.
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