High-voltage-activated calcium currents in neurons acutely isolated from the ventrobasal nucleus of the rat thalamus

We studied the high-voltage-activated (HVA) calcium currents in cells isolated from the ventrobasal nucleus of the rat thalamus with the use of the whole cell patch-clamp technique. Low-voltage-activated current was inactivated by the use of long voltage steps or 100-ms prepulses to -20 mV. We used channel blocking agents to characterize the currents that make up the HVA current. The dihydropyridine (DHP) antagonist nimodipine (5 microM) reversibly blocked 33 +/- 1% (mean +/- SE), and omega-conotoxin GVIA (1 microM) irreversibly blocked 25 +/- 5%. The current resistant to DHPs and omega-conotoxin GVIA was inhibited almost completely by omega-conotoxin MVIIC (90 +/- 5% at 3-5 microM) and was partially inhibited by omega-agatoxin IVA (54 +/- 4% block at 1 microM). We conclude that there are at least four main HVA currents in thalamic neurons: N current, L current, and two omega-conotoxin MVIIC-sensitive currents that differ in their sensitivity to omega-agatoxin IVA. We also examined modulation of HVA currents by strong depolarization and by G protein activation. Long (approximately 1 s), strong depolarizations elicited large, slowly deactivating tail currents, which were sensitive to DHP antagonists. With guanosine 5'-0-(3-thiotriphosphate) (GTP-gamma-S) in the intracellular solution, brief (approximately 20 ms), strong depolarization produced a voltage-dependent facilitation of the current (44 +/- 5%), compared with cells with GTP (22 +/- 7%) or guanosine 5'-O-(2-thiodiphosphate) (7 +/- 4%). However, the HVA current was inhibited only weakly by 100 microM acetylcholine (8 +/- 4%). Effects of the gamma-aminobutyric acid-B agonist baclofen were variable (3-39% inhibition, n = 12, at 10-50 microM).     

Dosimetry of copper-64-labeled monoclonal antibody 1A3 as determined by PET imaging of the torso

We present biodistribution and dosimetry results for 64Cu-benzyl-TETA-MAb 1A3 from 15 human subjects injected with this tracer as determined by serial PET imaging of the torso. METHODS: PET imaging was used to quantify in vivo tracer biodistribution at two time points after injection. Absorbed dosimetry calculated using MIRD-11 and the updated MIRDOSE3 was compared with estimates obtained using rat biodistribution data. RESULTS: By measuring activity concentrations in the torso, and extrapolating for the whole body using standard organ and tissue volumes, we were able to account for 93% of the injected radiopharmaceutical over a range of imaging times from 0 to 36 hr postinjection. Based on PET imaging and the MIRD-11 schema, the liver and spleen are the critical organs with average absorbed doses of 0.12 and 0.10 mGy/MBq (0.44 and 0.39 rad/mCi). The revised MIRDOSE3 scheme yields similar values for these and other organs but also results in a dose of 0.14 mGy/MBq (0.53 rad/mCi) to the heart wall. In the rat, the large intestine is the critical organ at 0.14 mGy/MBq (0.52 rad/mCi), while liver and kidneys each receive 0.11 mGy/MBq (0.41 rad/mCi). Some disparities in absorbed doses determined by these methods are evident but are a result of dissimilar biodistributions in rats and humans. For most organs, rat extrapolated values are higher than the human measurements with PET. CONCLUSION: This study shows that torso PET imaging can quantitatively measure the whole-body biodistribution of a radiopharmaceutical as long as it has relatively slow pharmacokinetics.     

Employee response to a company-sponsored program of colorectal and prostate cancer screening

Studies done in the mid-1970s documented increased risk for respiratory cancer and leukemia among employees in a chemical company manufacturing plant where chloromethyl ethers were used in production from 1948 to 1971. In the late 1980s, the company informed current and former employees about the results of follow-up studies which showed a moderation of risk of respiratory cancer and leukemia. New data showing elevated rates of mortality from colorectal, prostate, bladder, and pancreatic cancer in the population were also reported. Via mailed correspondence, the company made a no-cost program of colorectal and prostate cancer screening available to employees upon request; and information about bladder and pancreatic cancer was made available. Thirteen percent of employees in the population indicated interest in colorectal and prostate cancer screening (response). Thirty-one percent of these responders were screened (adherence). Multivariate analyses showed that education and length of employment in the plant were positively associated with response. Being white was positively associated with response for younger workers; while among older workers being male was positively associated with response. In terms of adherence, we found that older, more highly educated workers were more likely to have a screening examination. Findings indicate that employee participation in workplace-sponsored colorectal and prostate cancer screening can vary according to worker sociodemographic factors and length of employment in areas of potential exposure.     

A dilemma in analysis: issues in the serial measurement of quality of life in patients with advanced lung cancer

Despite the availability of several instruments to evaluate quality of life (QL) over time in patients with lung cancer, barriers in measurement remain. This methodological study used LCSS data (Lung Cancer Symptom Scale, a disease- and site-specific QL measure) to examine analysis methods to quantify QL where data needed for serial evaluation may be missing. Data from two large randomized trials, conducted at 30 centers, of a new combination chemotherapy regimen incorporating a new agent for patients (n = 673) with Stage III and IV non-small cell lung cancer were obtained for this study. QL had been prospectively measured at baseline, day 29, and every six weeks thereafter using the LCSS. For the slope analysis (SA) and area under the curve (AUC) analyses, an adjustment score of zero was used to indicate QL on the day of death (mortality adjustment) and each subsequent day until the end of the assessment period. Significant differences in QL, symptom scores and known prognostic factors at baseline were found in the attrition group. SA and AUC analysis allowed inclusion of 581 patients, giving an adequacy rate of 86%. By using a mortality adjustment, an additional 45 patients were included, increasing the inclusion rate to 93%. With the use of the mortality adjustment, QL was shown to decline over the interval, as opposed to rise if the adjustment had not been performed. The conclusions of the study were: (1) analysis for serial data using SA and AUC provides useful, but differing information; (2) when attrition (caused by death) is a factor, a mortality adjustment presented a more accurate assessment of QL as an endpoint; (3) more frequent evaluations of QL will capture rapid changes in patient status and reduce the attrition bias; (4) all patients should be followed until they die; and (5) QL should be given full consideration as a primary endpoint separate from survival.     

G protein alpha subunit G alpha z couples neurotransmitter receptors to ion channels in sympathetic neurons

The functional roles subserved by G(alpha)z, a G protein alpha subunit found predominantly in neuronal tissues, have remained largely undefined. Here, we report that G(alpha)z coupled neurotransmitter receptors to N-type Ca2+ channels when transiently overexpressed in rat sympathetic neurons. The G(alpha)z-mediated inhibition was voltage dependent and PTX insensitive. Recovery from G(alpha)z-mediated inhibition was extremely slow but accelerated by coexpression with RGS proteins. G(alpha)z selectively interacted with a subset of receptors that ordinarily couple to N-type Ca2+ channels via PTX-sensitive Go/i proteins. In addition, G(alpha)z rescued the activation of heterologously expressed GIRK channels in PTX-treated neurons. These results suggest that G(alpha)z is capable of coupling receptors to ion channels and might underlie PTX-insensitive ion channel modulation observed in neurons under physiological and pathological conditions.     

Extracellular matrix for a rechargeable cell delivery system

Above a critical concentration, aqueous polymer solutions of N-isopropylacrylamide copolymers with small amounts of acrylic acid, synthesized in benzene by radical polymerization, exhibited four distinct phases as the temperature increased; clear solution, opaque solution, gel and shrunken gel. The transition between the opaque solution phase and the gel phase was in the range of 30-34 degrees C and was reversible without syneresis and noticeable hysteresis under the experimental conditions used in this study. Islets of Langerhans, isolated from Sprague-Dawley rat pancreata and entrapped in the gel matrix, remained viable, with no significant decrease in insulin secretion function in vitro for one month. When islets were encapsulated with the gel matrix in hollow fibers [molecular weight cut-off (MWCO)= approximately 400000] and were exposed to dynamic changes in glucose and theophylline concentrations, their insulin secretion patterns demonstrated a smaller lag time and higher amplitude in insulin release than islets entrapped in a conventional alginate matrix under the same experimental conditions. From these two observations, i.e. gel reversibility and islet functionality in the matrix observed in in vitro experiments, the N-isopropylacrylamide copolymers with acrylic acid synthesized in this study are optimum candidates for the extracellular matrix in a diffusion chamber-type cell delivery system in order to recharge the entrapped cells when cell functionality in the system decreases.     

Resection of the metatarsal head for diabetic foot ulcers

Dobutamine-induced hypotension has been disregarded as a marker of more severe functional abnormalities in patients with suspected coronary artery disease. However, its functional significance in patients with myocardial infarction has not been studied. The aim of this study was to define the predictors of systolic blood pressure (SBP) response to dobutamine in patients with previous myocardial infarction. Dobutamine stress (up to 40 microg/kg per minute) echocardiography was performed in 326 patients with prior myocardial infarction referred for evaluation of myocardial ischemia. A 16-segment, four-grade score model was used to assess left ventricular function. Wall motion score index was derived by summation of wall motion score divided by 16. SBP and heart rate increased from rest to peak dobutamine stress (127 +/- 22 vs 134 +/- 27 mm Hg and 72 +/- 14 vs 122 +/- 24 bpm, p < 0.00001 in both). An increase of SBP > or = 30 mm Hg occurred in 50 patients (15%). By multivariate analysis, independent predictors of failure of SBP increase were higher peak wall motion score index (p < 0.001), higher resting SBP (p < 0.01), and medication with calcium channel blockers (p < 0.05). SBP drop > or = 20 mm Hg occurred in 54 patients (17%). Independent predictors of SBP drop were higher resting wall motion score index (p < 0.001), higher resting SBP (p < 0.0001), and older age (p < 0.05). In patients with myocardial infarction, left ventricular function and baseline systolic blood pressure are powerful predictors of SBP response to dobutamine stress testing.