No abstract

Purpose-To prospectively demonstrate the feasibility of using indocyanine green, a nearinfrared (NIR) fluorophore at the minimum dose needed for noninvasive optical imaging of lymph nodes (LNs) in breast cancer patients undergoing sentinel lymph node mapping (SLNM).Materials and Methods-Informed consent was obtained from 24 women (age range, 30-85 years) who received intradermal subcutaneous injections of 0.31-100 μg indocyanine green in the breast in this IRB-approved, HIPAA-compliant, dose escalation study to find the minimum microdose for imaging. The breast, axilla, and sternum were illuminated with NIR light and the fluorescence generated in the tissue was collected with an NIR-sensitive intensified chargedcoupled device. Lymphoscintigraphy was also performed. Resected LNs were evaluated for the presence of radioactivity, blue dye accumulation, and fluorescence. The associations between the resected LNs that were fluorescent and (a) the time elapsed between NIR fluorophore administration and resection and (b) the dosage of NIR fluorophores were tested with the Spearman rank and Pearson product moment correlation tests, respectively.Results-Lymph imaging consistently failed with indocyanine green microdosages between 0.31 and 0.77 μg. When indocyanine green dosages were 10 μg or higher, lymph drainage pathways from the injection site to LNs were imaged in eight of nine women; lymph propulsion was observed in seven of those eight. When propulsion in the breast and axilla regions was present, the mean apparent velocities ranged from 0.08 to 0.32 cm/sec, the time elapsed between "packets" of propelled fluid varied from 14 to 92 seconds. In patients who received 10 μg of indocyanine green or more, a weak negative correlation between the fluorescence status of resected LNs and the time © RSNA, 2008 Address correspondence to E.M.S. (evas@bcm.tmc.edu). Supplemental material: http://radiology.rsnajnls.org/cgi/content/full/2463070962/DC1 Author contributions:Guarantor of integrity of entire study, E.M.S.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, all authors; clinical studies, all authors; statistical analysis, all authors; and manuscript editing, all authors See Materials and Methods for pertinent disclosures. NIH Public Access Author ManuscriptRadiology. Author manuscript; available in PMC 2011 September 3. Conclusion-NIR fluorescence imaging of lymph function and LNs is feasible in humans at microdoses that would be needed for future molecular imaging of cancer-positive LNs.Currently, standard-of-care staging of breast cancer requires surgical resection of the first tumor-draining, or sentinel, lymph node (SLN) for subsequent pathologic examination (1). If the SLN is cancerous, then additional lymph nodes (LNs) in the axillary basin are subsequently removed for accurate staging. Recently, the a...

99m Tc-EC20 is a folate receptor (FR)-targeted imaging agent consisting of the vitamin folate conjugated to 99m Tc. FR is expressed on a variety of epithelial cancers, with advanced cancers often expressing FR at significantly higher levels than earlier stages of the disease. The goals of this pilot study were to determine the percentages of various solid tumors that accumulate 99m Tc-EC20 in vivo and to correlate 99m Tc-EC20 uptake with immunohistochemistry (IHC) analysis of FR expression in available biopsied tumor tissue. Methods: A total of 154 patients with proven or suspected cancer and at least one lesion of $1.5 cm underwent imaging with 99m Tc-EC20. The majority of these patients (77%) had a diagnosis of renal cell carcinoma. The remaining patients had a variety of other solid tumors. Whole-body planar images were obtained 1-2 h after injection, followed by SPECT of the region containing index lesions. The uptake of 99m Tc-EC20 in tumors was scored as no uptake, mild uptake, or marked uptake. The resultant 99m Tc-EC20 data were analyzed for correlation with the expression of the a-isoform of FR, as determined by IHC analysis, in tissue available from prior or subsequent surgery or biopsy. Results: The administration of 99m Tc-EC20 was well tolerated. Tumors with increased 99m Tc-EC20 uptake were identified in 68% of patients, and IHC results were positive for the expression of the a-isoform of FR in 67% of patients. The agreement between methods was 61% overall (k 5 0.096; 95% confidence interval 5 20.085 to 0.277), with 72% agreement of positive results and 38% agreement of negative results. Conclusion: In vivo imaging with 99m Tc-EC20 identified approximately two thirds of patients as having FR-positive tumors. Agreement between imaging and in vitro IHC was poor but was potentially confounded by a lack of correlation between the time of tissue sampling and the time of 99m Tc-EC20 imaging, the heterogeneous expression of FR in metastatic lesions from the same patient, and the inability to detect the b-isoform of FR by IHC. This pilot study of 99m Tc-EC20 scintigraphy indicates that the agent is safe and well tolerated and that this noninvasive procedure may have utility in selecting patients likely to benefit from FR-targeted therapy.

1. The properties of single voltage-gated calcium channels were investigated in acutely exposed CA3 and CA1 pyramidal neurons and granule cells of area dentata in the adult guinea pig hippocampal formation. 2. Guinea pig hippocampal slices were prepared in a conventional manner, then treated with proteolytic enzymes and gently shaken to expose the somata of the three cell types studied. Standard patch-clamp techniques were used to record current flow through calcium channels in cell-attached membrane patches with isotonic barium as the charge carrier. 3. Single-channel current amplitudes were measured at different membrane potentials. Single-channel current-voltage plots were constructed and single-channel slope conductances were found to fall into three classes. These were (approximately) 8, 14, and 25 pS, and were observed in all three cell types. 4. The three groups of channels differed from each other in voltage dependence of activation: from a holding potential of -80, the small-conductance channel began to activate at about -40 to -30 mV, the medium-conductance channel at about -20 mV, and the large-conductance channel at approximately 0 mV. 5. Ensemble averages of single-channel currents during voltage steps revealed differences in voltage-dependent inactivation. The small-conductance channel inactivated completely within approximately 50 ms during steps from -80 to -10 mV or more positive. Steps to less positive potentials resulted in less inactivation. The medium-conductance channel displayed variable inactivation during steps from -80 to 0 mV. Inactivation of this channel during a 160-ms step ranged from virtually zero to approximately 100%. The large-conductance channel displayed no significant inactivation during steps as long as 400 ms. 6. The large-conductance channel was strikingly affected by the dihydropyridine agonist Bay K8644 (0.5-2.0 microM), resulting in a high probability of channel opening, prolonged openings, and an apparent increase in the number of channels available for activation. The medium and small-conductance channels were not noticeably affected by the drug. 7. The large-conductance channel could be induced to open at very negative membrane potentials by holding the patch for several seconds at 20 or 30 mV and stepping to -30 or -40 mV. This process was enhanced by Bay K8644, resulting in prolonged openings at potentials as negative as -100 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

No abstract

Considerable evidence suggests that cognitive state affects local levels of neurotransmitter in the brain. We introduce a compartment model of neuroreceptor ligand kinetics to describe the effect of change in cognitive state on positron emission tomography (PET) signal dynamics. The model is used to establish optimal experimental conditions, timing of activation, and ligand characteristics, for detecting cognitive activation. The model, which follows free and bound endogenous neurotransmitter, describes the PET curve predicted for a single injection of radioligand in the presence or absence of activation. Activation was conceptualized as the performance of a task that raises the level of neurotransmitter that competes for receptor sites with the radioligand. Simulating the dopamine system, for example, required making assumptions regarding the kinetic rate constants for binding/dissociation of endogenous dopamine to/from the receptor and dopamine concentrations in the synapse. Simulations suggest that activation of dopamine should be detectable with PET and the D2 receptor ligand [llC]raclopride, although this ligand might not be optimal. Aspects of experimental design can be modified to optimize the likelihood of detecting neurotransmitter changes. The ideal radioligand for these studies should bind irreversibly to its receptor. Furthermore, the task should commence at injection time and last for at least 7 minutes. Optimal task duration depends on the dynamics of free radioligand in the tissue and can be determined via model simulations for any well-characterized receptor ligand. Flow effects were shown to be distinguishable from those of neurotransmitter activation. General principles regarding desirable ligand characteristics and activation timing held for both the D2 receptor and the dopamine transporter site. o 1995 Wiley-Liss, Inc.

1. Pharmacologic agents known to modulate long-term potentiation (LTP) at the mossy fiber-to-CA3 pyramidal neuron synapse were tested for their effects on the activity of single voltage-gated calcium channels in adult CA3 pyramidal neurons. 2. Single-channel current recordings of three types of voltage-gated calcium channels were made from acutely exposed CA3 pyramidal neurons of the adult guinea pig hippocampus. 3. The beta-adrenergic agonist isoproterenol (10 microM), which is known to enhance LTP, increased the activity of the two high-threshold calcium channels (N and L) with no striking effect on the low-threshold (T) channel. 4. The muscarinic agonists carbachol and muscarine (1-10 microM), the latter of which has been shown to inhibit LTP, decreased the probability of opening of L channels, increased the probability of opening of T channels, and had no effect on N channels. The effects were blocked by 0.1 microM atropine. 5. These results are consistent with the hypothesis that neuromodulation of mossy fiber LTP occurs, at least in part, through the modulation of postsynaptic, voltage-gated calcium channels.

Recent data from positron emission tomography (PET) imaging studies suggest the possibility of studying synaptic transmission in vivo in humans. The approach will require a synthesis of two established techniques: brain activation studies (conventionally performed by measuring regional cerebral blood flow or metabolism) and neurotransmitter receptor imaging (using radiolabelled ligands that bind to specific neuroreceptors). By comparing neuroreceptor binding in subjects at rest and while performing an activation task, it may be possible to determine whether a particular neurotransmitter is involved in performance of the task. The underlying principle is that endogenous neurotransmitter competes with the injected radioligand for the same receptors, thereby inhibiting ligand binding. This effect will be even more pronounced during activation, as the synaptic concentration of transmitter rises. Thus, activation of a specific neurotransmitter will be detected as a decrease in specific binding of the radioligand. In this paper we review neurophysiological and biochemical literature to estimate the endogenous neurotransmitter concentration changes that will be expected to occur during an activation task, using the dopamine system as an example. We calculate that the average synaptic dopamine concentration is = l o 0 nM and that it approximately doubles during activation. This, along with consideration of the concentration of radioligand and affinities of the ligand and dopamine for dopamine receptors, suggests that physiological activation of a specific neurotransmitter system is likely to be detectable with PET. D 1995 wiley-Liss, inc.