Abstract: The major active ingredient of marijuana, (−)-Δ9-tetrahydrocannabinol, exerts its psychoactive effects via binding to cannabinoid CB1 receptors, which are widely distributed in the brain. Radionuclide imaging of CB1 receptors in living human subjects would help explore the presently unknown physiological roles of this receptor system, as well as the neurochemical consequences of marijuana dependence. Currently available cannabinoid receptor radioligands are exceedingly lipophilic and unsuitable for in vivo use. We report the development of a novel radioligand, [123I]AM281{ N -(morpholin-4-yl)-5-(4-[123I]iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1 H -pyrazole-3-carboxamide}, that is structurally related to the CB1-selective antagonist SR141716A [ N -(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1 H -pyrazole-3-carboxamide]. Baboon single photon emission computed tomography studies, mouse brain dissection studies, and ex vivo autoradiography in rat brain demonstrated rapid passage of [123I]AM281 into the brain after intravenous injection, appropriate regional brain specificity of binding, and reduction of binding after treatment with SR141716A. AM281 has an affinity in the low nanomolar range for cerebellar binding sites labeled with [3H]SR141716A in vitro, and binding of [123I]AM281 is inhibited by several structurally distinct cannabinoid receptor ligands. We conclude that [123I]AM281 has appropriate properties for in vivo studies of cannabinoid CB1 receptors and is suitable for imaging these receptors in the living human brain. 相似文献
Activation of phospholipase Cβ (PLCβ) by G proteins leads to a chain of events that result in an increase in intracellular calcium and activation of protein kinase C (PKC). It has been found that PKC phosphorylates PLCβ1 on S887 in vitro without affecting its enzymatic activity or its ability to be activated by Gα(q) proteins. To understand whether S887 phosphorylation affects the enzyme’s activity in cells, we constructed two mutants that mimic the wild type and PKC-phosphorylated enzymes (S887A and S887D). We find that these constructs bind similarly to Gα(q) in vitro. When expressed in HEK293 cells, both mutants associate identically to Gα(q) in both the basal and stimulated states. Both mutants diffuse with similar rates and also interact identically with another known binding partner, translin-associated factor X (TRAX), which associates with PLCβ1 in the cytosol and nucleus. However, the two mutants localize differently in the cell. We find that S887A has a much higher nuclear localization than its S887D counterpart both in HEK293 cells and PC12 cells. Our studies suggest that PKC phosphorylation regulates the level of PLCβ1 cytosolic and nuclear activity by regulating its cellular compartmentalization. 相似文献
Biological tissues are very strong light‐scattering media. As a consequence, current medical imaging devices do not allow deep optical imaging unless invasive techniques are used. Acousto‐optic imaging is a light‐ultrasound coupling technique that takes advantage of the ballistic propagation of ultrasound in biological tissues to access optical contrast with a millimeter resolution. We have developed a photorefractive‐crystal‐based system that performs self‐adaptive wavefront holography and works within the optical therapeutic window. As it works at an appropriate wavelength range for biological tissues imaging, it was tested on ex vivo liver samples containing tumors as a pre‐clinical study. Optical contrast was obtained even if acoustical one was not significant.
Ultrasound image (left) and acousto‐optic image (right) of a liver biopsy with tumors. Acousto‐optic imaging exhibits tumors that are not detected through ultrasound. 相似文献
The early detection of both primary tumors and metastatic disease continue to be significant challenges in the diagnosis and staging of cancer. The growing recognition of the role of proteinases and proteolytic cascades in both the growth and metastasis of tumors has led to the development not only of therapeutic strategies using proteinase inhibitors, but also of methods to detect and image tumors in vivo via tumor-associated proteolytic activities. These imaging strategies derive from the enhanced sensitivity afforded by amplification that can be obtained by enzymatic processing to increase the efficacy of imaging "contrast agents" coupled with the inherent substrate specificity and selectivity of proteinases. This review describes key proteinases important in cancer progression, the strategies that have been devised to detect and image proteolytic activity in vivo, and the potential for this kind of functional imaging to serve as a marker for targeted therapy. The intent is to draw attention to the developing methods of molecular imaging to facilitate not only cancer diagnosis, but also for devising strategies for individualized targeted therapy and non-invasive monitoring of therapeutic efficacy. 相似文献
Many anticancer drugs activate caspases via the mitochondrial apoptosis pathway. Activation of this pathway triggers a concomitant bioenergetic crisis caused by the release of cytochrome‐c (cyt‐c). Cancer cells are able to evade these processes by altering metabolic and caspase activation pathways. In this study, we provide the first integrated system study of mitochondrial bioenergetics and apoptosis signalling and examine the role of mitochondrial cyt‐c release in these events. In accordance with single‐cell experiments, our model showed that loss of cyt‐c decreased mitochondrial respiration by 95% and depolarised mitochondrial membrane potential ΔΨm from ?142 to ?88 mV, with active caspase‐3 potentiating this decrease. ATP synthase was reversed under such conditions, consuming ATP and stabilising ΔΨm. However, the direction and level of ATP synthase activity showed significant heterogeneity in individual cancer cells, which the model explained by variations in (i) accessible cyt‐c after release and (ii) the cell's glycolytic capacity. Our results provide a quantitative and mechanistic explanation for the protective role of enhanced glucose utilisation for cancer cells to avert the otherwise lethal bioenergetic crisis associated with apoptosis initiation. 相似文献
Urodele amphibians regenerate appendages through the recruitment of progenitor cells into a blastema that rebuilds the lost tissue. Blastemal formation is accompanied by extensive remodeling of the extracellular matrix. Although this remodeling process is important for appendage regeneration, it is not known whether the remodeled matrix directly influences the generation and behavior of blastemal progenitor cells. By integrating in vivo 3-dimensional spatiotemporal matrix maps with in vitro functional time-lapse imaging, we show that key components of this dynamic matrix, hyaluronic acid, tenascin-C and fibronectin, differentially direct cellular behaviors including DNA synthesis, migration, myotube fragmentation and myoblast fusion. These data indicate that both satellite cells and fragmenting myofibers contribute to the regeneration blastema and that the local extracellular environment provides instructive cues for the regenerative process. The fact that amphibian and mammalian myoblasts exhibit similar responses to various matrices suggests that the ability to sense and respond to regenerative signals is evolutionarily conserved. 相似文献