Impact of physicochemical properties of engineered fullerenes on key biological responses.

Engineered fullerenes are widely integrated into several commercial and medical products and are now also being recognized as byproducts of many industrial activities. For most applications fullerenes have to be chemically modified. Surface modification of fullerenes can potentially impact their effect on biosystems. The purpose of the current study was to establish criteria to correlate fullerene structure to biological responses. We report studies of cellular responses induced by three different types of fullerenes that provide varying chemical and physical properties such as electronic behavior, solubility, and degree of agglomeration. Using a systematic and multipronged approach for material characterization and employing critical biological endpoints, we determined the impact of the physicochemical properties of fullerenes on cellular interactions. We examined the ability of these fullerenes to regulate intracellular oxidative stress, necrosis and apoptosis in human monocytic THP1 cells. Results indicate that the carboxylate derivatization of fullerenes was the determining factor in their ability to induce apoptosis. In contrast, the dispersion characteristics of fullerenes were found to be more relevant when considering their redox function. We also established a significant role for functionalization-dependent fullerene-regulation of the caspase proteases in the elicited responses. In addition, there was a notable increase in the level of several anti-oxidant enzymes. Collectively, the results clearly indicate that the physicochemical properties of fullerenes significantly influence the elicited biological response, thus impacting future applications. This study is an initial effort to lay the groundwork for routine correlation and predictive analysis on engineered fullerenes, thus expediting their use.

Radionuclide imaging of the adrenal cortex.

Adrenocortical scintigraphy provides information concerning cortical function that is not readily available by other means. The ability to map differential adrenal cortical function has great clinical utility and demonstrable cost-effectiveness in the evaluation of adrenocortical disease and in distinguishing benign from malignant lesions in patients with incidentally discovered adrenal masses.

Pitfalls in oncologic diagnosis with FDG PET imaging: physiologic and benign variants.

A rapidly emerging clinical application of positron emission tomography (PET) is the detection and staging of cancer with the glucose analogue tracer 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG). Proper interpretation of FDG PET images requires knowledge of the normal physiologic distribution of the tracer, frequently encountered physiologic variants, and benign pathologic causes of FDG uptake that can be confused with a malignant neoplasm. One hour after intravenous administration, high FDG activity is present in the brain, the myocardium, and--due to the excretory route--the urinary tract. Elsewhere, tracer activity is typically low, a fact that allows sensitive demonstration of tracer accumulation in many malignant neoplasms. Interpretive pitfalls commonly encountered on FDG PET images of the body obtained 1 hour after tracer administration can be mistaken for cancer. Such pitfalls include variable physiologic FDG uptake in the digestive tract, thyroid gland, skeletal muscle, myocardium, bone marrow, and genitourinary tract and benign pathologic FDG uptake in healing bone, lymph nodes, joints, sites of infection, and cases of regional response to infection and aseptic inflammatory response. In many instances, these physiologic variants and benign pathologic causes of FDG uptake can be specifically recognized and properly categorized; in other instances, such as the lymph node response to inflammation or infection, focal FDG uptake is nonspecific.

Diagnosis of spine metastases by FDG imaging using a gamma camera in the coincidence mode.

PURPOSE: To illustrate the detection of metastatic lung cancer using a conventional dual detector gamma camera modified to operate in the coincidence mode to image the static distribution of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG). METHODS: A patient with known lung cancer underwent FDG imaging to evaluate the extent of metastatic disease. Twenty-three-minute emission image acquisition at one bed position using a dual detector coincidence gamma camera was performed to evaluate the entire chest and upper abdomen. RESULTS: In addition to detecting the malignant lung nodule, mediastinal lymph node metastases and a rib metastasis, symptomatic metastases to lower thoracic and upper lumbar vertebral bodies, which were not identified on radiographs, CT, or bone scan, were shown clearly by FDG coincidence gamma camera imaging. CONCLUSION: FDG tumor imaging in the body is feasible using a dual detector gamma camera operating in coincidence mode and may find an important role in a certain subset of FDG tumor imaging.

Oncologic diagnosis with 2-[fluorine-18]fluoro-2-deoxy-D-glucose imaging: dual-head coincidence gamma camera versus positron emission tomographic scanner.

PURPOSE: To compare the performance of a dual-head single photon emission computed tomographic (SPECT) Anger camera operated in coincidence mode with that of a dedicated positron emission tomographic (PET) scanner in the imaging of cancer with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG). MATERIALS AND METHODS: Thirty-one patients with known or suspected malignant neoplasms underwent imaging with both methods, and the images were read blindly. Diagnostic performance on a lesion-by-lesion basis was compared with attenuation-corrected PET as the standard of reference. RESULTS: Of a total of 109 discrete lesions depicted at PET, 60 (relative sensitivity, 55%) were identified on the coincidence-mode images. Of the nodules or masses depicted at PET, 13 (93%) of 14 lung nodules or masses, 20 (65%) of 31 mediastinal lymph nodes, five (71%) of seven lesions in the neck, five (55%) of nine axillary lymph nodes, 11 (50%) of 22 bone metastases, and six (23%) of 26 abdominal tumor deposits were correctly identified on the coincidence gamma camera images. CONCLUSION: These preliminary findings indicate FDG imaging with a modified dual-detector gamma camera operating in coincidence mode can depict many of the lesions depicted with a PET scanner, particularly in the lungs. Sensitivity for lesions detected at dedicated FDG PET was poor in the abdomen and in all locations outside the lungs for tumor deposits generally less than 1.5 cm in short-axis diameter.

Focal fluorine-18 fluorodeoxyglucose accumulation in inflammatory pancreatic disease.

Focal 2-deoxy-2[fluorine-18]fluoro-D-glucose (FDG) uptake on positron emission tomography (PET) in a pancreatic mass has been reported as a specific finding for pancreatic carcinoma. Inflammatory conditions of the pancreas and associated clinical circumstances yielding similar findings have not yet been fully defined. Among 42 patients studied by attenuation-corrected FDG PET for pancreatic disease, 12 with focal FDG uptake in the pancreas were identified as having no underlying neoplasm based on surgical findings, biopsy results, and long term clinical and imaging follow up. Focal FDG accumulation in the pancreas with standardized uptake values ranging from 3.4 to 11.2 on FDG PET was ultimately found to be related to inflammation rather than neoplasm. This occurred in pancreatic masses in which clinical and laboratory evidence of acute pancreatitis was equivocal or entirely lacking, as well as in the setting of acute pancreatitis and after recovery from acute pancreatitis. Inflammation can give rise to focal FDG uptake in the same intensity range as pancreatic neoplasm, even when clinical, laboratory and computed tomographic findings suggestive of an inflammatory etiology are equivocal or absent.

Imaging of the pancreas and related diseases with PET carbon-11-acetate.

UNLABELLED: The purpose of this study was to evaluate [1-11C]-acetate as a tracer for functional imaging of the pancreas and related diseases using position emission tomography (PET). METHODS: Thirty-three patients underwent 30 min of dynamic attenuation-corrected PET after intravenous administration of 740 MBq (20 mCi) of [1-11C]-acetate. RESULTS: The normal pancreas demonstrates prompt uptake of [1-11C]-acetate and is visualized as early as 2 min post-injection, with maximal activity achieved by 5 min. Subsequent clearance of tracer from the pancreas is slow relative to adjacent organs and background, such that by 10 min post-injection the pancreas is the most prominent organ in the imaging field of view. Pancreatic uptake of [1-11C]-acetate was unaffected by pancreatic endocrine insufficiency, but is absent in chronic pancreatitis complicated by exocrine insufficiency. Moderately reduced [1-11C]-acetate uptake was observed in acute uncomplicated pencreatitis. The level of tracer accumulation was substantially reduced in phlegmatous masses complicating pancreatitis and in chronic mass forming pancreatitis. Adenocarcinoma of the pancreas likewise demonstrated no significant uptake of [1-11C]-acetate. CONCLUSIONS: Accumulation of [1-11C]-acetate by the pancreas allows rapid metabolic imaging using PET, and may be a useful metabolic probe for the study of pancreatic physiology and disease.

Metastatic prostate cancer: initial findings of PET with 2-deoxy-2-[F-18]fluoro-D-glucose.

PURPOSE: To evaluate the accuracy of positron emission tomography (PET) with 2-deoxy-2-[fluorine-18] fluoro-D-glucose (FDG) in the detection of osseous and soft-tissue metastases of prostate cancer. MATERIALS AND METHODS: Thirty-four patients (mean age, 71 years) with biopsy-proved prostate cancer and known or suspected metastatic disease were examined. Blinded interpretation of the PET images was compared with bone scan, CT, and clinical follow-up findings. RESULTS: In 202 untreated osseous metastases in 22 patients, the sensitivity of FDG PET was 65% (131 of 202 metastases), with a positive predictive value of 98% (131 of 133 positive findings). The estimated standardized uptake value in metastases was 2.1-5.7. Soft-tissue metastases to the lymph nodes or liver were identified, but evaluation of pelvic lymph node metastases was severely limited because of bladder tracer activity. CONCLUSION: FDG PET can help identify osseous and soft-tissue metastases of prostate cancer with a high positive predictive value but is less sensitive than bone scintigraphy in the identification of osseous metastases.

Simultaneous transmission/emission myocardial perfusion tomography. Diagnostic accuracy of attenuation-corrected 99mTc-sestamibi single-photon emission computed tomography.

BACKGROUND: The purpose of the present study was to assess the diagnostic performance of attenuation-corrected (AC) stress 99mTc-sestamibi cardiac single-photon emission computed tomography (SPECT) for the identification of coronary heart disease (CHD). METHODS AND RESULTS: With a triple-detector SPECT system with a 241Am transmission line source, simultaneous transmission/emission tomography (TCT/ECT) was performed on 60 patients with angiographic coronary disease and 59 patients with < or = 5% likelihood of CHD. Iteratively reconstructed AC stress 99mTc-sestamibi perfusion images were compared with uncorrected (NC) filtered-backprojection images. Normal database polar maps were constructed from AC and NC images for quantitative analyses. From the low-likelihood patients, the visual and quantitative normalcy rates increased from 0.88 and 0.76 for NC to 0.98 and 0.95 for AC (P < .05). For the detection of CHD, the receiver operating characteristic curves for the AC images demonstrated improved discrimination capacity (P < .05), and sensitivity/specificity values increased from 0.78/0.46 (NC) to 0.84/0.82 (AC) with visual analysis and from 0.84/0.46 (NC) to 0.88/0.82 (AC) with quantitative analysis. For localization of stenosed vessels, visual and quantitative sensitivity values were 0.51 and 0.63 for NC and 0.64 and 0.78 for AC images (P < .05), respectively. CONCLUSIONS: TCT/ECT myocardial perfusion imaging significantly improves the diagnostic accuracy of cardiac SPECT for the detection and localization of CHD. Clinical use of TCT/ECT imaging deserves serious consideration.

Carbon-11-acetate PET imaging in renal disease.

UNLABELLED: The purpose of this study was to investigate the use of [1-11C]acetate as a metabolic tracer for renal imaging in human subjects. METHODS: Eighteen patients underwent dynamic PET imaging of the kidneys after intravenous bolus injection of 10-20 mCi [1-11C]acetate. Time-activity curves of renal parenchyma tracer activity were fitted to a two-compartment model using direct arterial blood sampling for the arterial input function. RESULTS: Renal uptake of [1-11C]acetate is prompt and high target-to-background ratios are achieved even in the presence of markedly reduced renal function. Carbon-11-acetate is cleared from the renal parenchyma without any urinary excretion and the rate of clearance is comparable to myocardial clearance rates. Among normal subjects, K1, ranged from 0.653 to 1.37 ml/min-g, and was reduced to as low as 0.363 ml/min-g in severe renal disease (serum creatinine greater than 5 mg/dl), while k2 ranged from 0.114 to 0.166 min-1 among normal subjects and was reduced to as low as 0.053 min-1 in severe renal disease. Kinetic parameters K1 and k2 were both reduced in the presence of intrinsic renal disease or significant renal artery stenosis. Renal cell carcinoma demonstrated similar uptake of [1-11C]acetate, but substantially reduced the rate of clearance compared to normal and diseased non-neoplastic renal tissue, allowing for ready differentiation of renal cell carcinoma from non-neoplastic renal tissue on images acquired beyond 10 min of tracer administration. CONCLUSION: Carbon-11-acetate is a promising physiologic tracer for the study of renal disease.

Triple-head SPECT with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG): initial evaluation in oncology and comparison with FDG PET.

PURPOSE: In patients with cancer, performance was assessed of a commercially available triple-head gamma camera fitted with ultra-high energy parallel-hole collimators performing single photon emission computed tomography (SPECT) with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG). Results were compared with those of positron emission tomography (PET) with FDG. MATERIALS AND METHODS: Performance characteristics were first determined in phantom studies for FDG PET and triple-head gamma camera SPECT systems. In 13 patients with malignancies, FDG PET was followed by SPECT of the same region, and imaging results were independently assessed. RESULTS: Sensitivity of the PET and SPECT systems was 58.3 counts/MBq/min and 4.5 counts/MBq/min, respectively. Reconstructed spatial resolution was approximately 7 mm for PET and 20 mm for SPECT. All known cancer foci were detected at PET. SPECT depicted 11 of the 22 lesions detected at PET, but only five of the 14 lesions less than 3 cm in diameter. CONCLUSION: FDG SPECT performed with a specially collimated triple-head gamma camera depicted some cancers but had an unacceptably low sensitivity compared with PET for lesions less than 3 cm in diameter. PET is preferable for detecting small cancers.

Synthesis of a nonpeptide carbon-11 labeled substance P antagonist for PET studies.

CP 96,345 is a nonpeptide high affinity antagonist of the substance P (NK1) receptor. The radiosynthesis of [11C]CP 96,345 suitable for Positron Emission Tomography (PET) applications is described. [11C]CP 96,345 was prepared by O-methylation of a desmethyl precursor via in situ generation of its phenolate salt. The in vivo tissue distribution of [11C]CP 96,345 in guinea pigs (n = 2) at 5 and 30 min was determined. Uptake was low in brain (approximately 0.04% dose/g) and highest (approximately 1-2% dose/g) in the spleen and lungs. The present findings indicate that the use of [11C]CP 96,345 in PET might be more applicable to the study of substance P receptors in peripheral tissues involved with inflammatory disease and arthritis.

Down-regulation of alpha 2-adrenoceptor subtypes.

To characterize further the alpha 2-adrenoceptor subtypes in terms of their regulation, monolayers of cells expressing either the alpha 2A (CHO-A2AR cells) or alpha 2C (OK cells) subtype were preincubated with norepinephrine for various times and the extent of receptor down-regulation was assessed. Exposure to 30 microM norepinephrine caused a similar time course and extent of down-regulation (approximately 50%) in both cells lines. The extent of down-regulation caused by 0.3 microM norepinephrine in OK cells was similar to that with 30 microM norepinephrine in CHO-A2AR cells, although the time course was somewhat slower. Reversal of the down-regulation of the alpha 2-adrenoceptor caused by 30 microM norepinephrine was more rapid in the CHO-A2AR than in the OK cell. With 0.3 microM norepinephrine, reversal of down-regulation of the alpha 2-adrenoceptor in the OK cell was slightly faster than that of the CHO-A2AR cell with 30 microM norepinephrine. These data indicate that although norepinephrine is more potent in causing down-regulation of the alpha 2C (OK cells) as compared to the alpha 2A subtype (CHO-A2AR cells), the time courses for down-regulation and its reversal are similar for the two subtypes.

GABA and glutamate interact in the substantia innominata/lateral preoptic area to modulate locomotor activity.

Previous studies have shown that excitatory amino acid agonists or GABAergic antagonists injected into the substantia innominata/lateral preoptic area (SI/LPO) can produce the stimulation of coordinated locomotor activity. The purpose of the present study was to determine whether GABAergic and glutamatergic mechanisms in the SI/LPO interact to regulate locomotor activity. The stimulation of locomotor activity produced by the bilateral injection into the SI/LPO of 0.5 microgram of AMPA, a potent quisqualic acid receptor agonist, was antagonized by the coinjection of muscimol (25 ng). Similarly, the stimulation of locomotor activity produced by picrotoxin, an inhibitor of the effects of GABA, was antagonized by the coinjection of DNQX, which has been shown to inhibit the behavioral effects of both kainic acid and quisqualic acid, or a high dose of GAMS (25 micrograms), which has been shown to inhibit the behavioral effects of both AMPA and N-methyl-D-aspartic acid. In contrast, a lower dose of GAMS (5 micrograms), which selectively inhibited the locomotor stimulation produced by AMPA, or D-alpha-aminoadipic acid, at a dose (10 micrograms) which selectively inhibited the locomotor stimulation produced by N-methyl-D-aspartic acid, did not inhibit the effects of picrotoxin. However, the combination of both GAMS (5 micrograms) and D-alpha-aminoadipic acid (10 micrograms) produced a marked inhibition of the response to picrotoxin. These results suggest that the hypermotility response elicited by picrotoxin can only be antagonized when more than one subtype of excitatory amino acid receptor is antagonized and support the concept that excitatory amino acid receptors and GABAergic receptors in the SI/LPO interact to regulate locomotor activity.

AMPA, kainic acid, and N-methyl-D-aspartic acid stimulate locomotor activity after injection into the substantia innominata/lateral preoptic area.

The substantia innominata/lateral preoptic area (SI/LPO) is a subpallidal region which has been shown to regulate the hypermotility produced by drugs acting in the nucleus accumbens. Evidence has been presented that the SI/LPO contains glutamatergic nerve terminals and receptors for excitatory amino acids. The purpose of this study was to determine the effects of the activation of excitatory amino acid receptors in the SI/LPO on locomotor activity following the direct injection of excitatory amino acids into this brain site. It was found that the bilateral injection of alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA), kainic acid, and N-methyl-D-aspartic acid into the SI/LPO produced marked dose-dependent stimulations of locomotor activity which resembled the effects of these agents after their injection into the nucleus accumbens. The effect, however, was bell-shaped in that at high doses, the locomotor activity values decreased from their peak values. The coinjection of gamma-glutamylaminomethylsulfonate (GAMS) with AMPA into the SI/LPO was found to inhibit the hypermotility response to AMPA at doses that were unable to produce a significant inhibition of the hypermotility responses to kainic acid or N-methyl-D-aspartic acid. The injection of 6,7-dinitroquinoxaline-2,3-dione (DNQX) into the SI/LPO inhibited the hypermotility responses to AMPA or kainic acid while having no significant inhibitory effect on N-methyl-D-aspartic acid stimulated locomotor activity. The injection of D-alpha-aminoadipic acid into the SI/LPO produced a significant inhibition of the hypermotility response produced by N-methyl-D-aspartic acid at a dose that did not produce a significant inhibition of the hypermotility response produced by AMPA.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of pretreatment with amphetamine on the interaction between amphetamine and dopamine neurons in the nucleus accumbens.

The present study was designed to examine the effect of pretreatment with amphetamine on the ability of amphetamine to release dopamine from slices of the nucleus accumbens and striatum and to stimulate locomotor activity or stereotyped behavior, after direct injection into either the nucleus accumbens or the striatum. Rats were injected twice daily for 5 days with either amphetamine (5 mg/kg, i.p.) or saline. At 33 days after this pretreatment, the release of endogenous dopamine from both regions of the brain in vitro by amphetamine and the changes in behavioral responses to the direct injection of amphetamine into either region were examined. Amphetamine at both 1 and 10 microM stimulated the release of endogenous dopamine from slices prepared from both of the brain areas. The release of dopamine by amphetamine was increased in rats pretreated with amphetamine. Consistent with its ability to stimulate endogenous release of dopamine, amphetamine, when injected into the nucleus accumbens, stimulated locomotor activity, while stereotyped behavior was enhanced when amphetamine was injected into the striatum. However, the locomotor activity and stereotyped behavioral responses to small doses of amphetamine (5, 10 or 25 micrograms) were not significantly greater in amphetamine-pretreated rats, compared to saline-pretreated animals. A greater stimulation of both responses in amphetamine-pretreated rats was only observed when a large dose (50 micrograms) of amphetamine was administered into either the nucleus accumbens or striatum.(ABSTRACT TRUNCATED AT 250 WORDS)