Synthesis and characterization of substituted benzoylhydrazones of naloxone.

Naloxone benzoylhydrazone (NalBzoH) has proved a valuable tool in the investigation of opioid receptor subtypes. In the present study, we have examined a series of derivatives of NalBzoH in which substitutions have been made on the benzoyl ring. Overall, we see dramatic effects on the binding affinities of derivatives against the various opioid receptor subtypes. Although the range of affinities against the mu receptors is quite modest, ranges of the others vary almost 30-fold for kappa 3, 50-fold for kappa 1 and 100-fold for delta and kappa 2 binding. Few substituted derivatives display greater affinity than NalBzoH for any of the receptors, except for delta sites where several derivatives have affinities almost tenfold greater than NalBzoH. Along with the wide variations in affinity, the compounds also appear to exhibited widely divergent activities in traditional bioassays.

Imaging of brain tumor proliferative activity with iodine-131-iododeoxyuridine.

METHODS: Iodine-131-iododeoxyuridine (IUdR) uptake and retention was imaged with SPECT at 2 and 24 hr after administering a 10-mCi dose to six patients with primary brain tumors. The SPECT images were directly compared to gadolinium contrast-enhanced MR images as well as to [18F]fluorodeoxyglucose (FDG) PET scans and 201Tl SPECT scans. RESULTS: Localized uptake and retention of IUdR-derived radioactivity was observed in five of six patients. The plasma half-life of [131I]IUdR was short (1.6 min) in comparison to the half-life of total plasma radioactivity (6.4 hr). The pattern of [131I]IUdR-derived radioactivity was markedly different in the 2-hr compared to 24-hr images. Radioactivity was localized along the periphery of the tumor and extended beyond the margin of tumor identified by contrast enhancement on MRI. The estimated levels of tumor radioactivity at 24 hr, based on semiquantitative phantom studies, ranged between < 0.1 and 0.2 microCi/cc (< 0.001% and 0.002% dose/cc); brain levels were not measurable. CONCLUSIONS: Iodine-131-IUdR SPECT imaging of brain tumor proliferation has low (marginal) sensitivity due to low count rates and can detect only the most active regions of tumor growth. Imaging at 24 hr represents a washout strategy to reduce 131I-labeled metabolites contributing to background activity in the tumors, and is more likely to show the pattern of [131I]IUdR-DNA incorporation and thereby increase image specificity. Iodine-123-IUdR SPECT imaging at 12 hr and the use of [124I]IUdR and PET will improve count acquisition and image quality.

Transport limits cellular entry of hepatic arterially injected 5-[18F]fluoro-2'-deoxyuridine in human intrahepatic tumors.

The causes of tumor resistance to hepatic arterially infused fluorodeoxyuridine (FdUrd) are poorly understood. A previous study showed that sufficient arterial perfusion relative to liver is necessary for tumor response. The present study examined the effect of transport on FdUrd flux from arterial blood into tumor cells. Five patients with large intrahepatic tumors (four with colorectal hepatic metastases, one with hepatoma) were given bolus hepatic arterial (HA) injections of [18F]FdUrd, and their livers imaged dynamically with a dual-detector gamma camera. Cellular entry of [18F]FdUrd was inferred by comparison with HA-injected 99mTc diethylenetriaminepentaacetate, an extracellular indicator. The images were analyzed to determine single-pass, blood-into-cell, extraction fractions [E(FdUrd)] and fractional retention of extracted radiolabel vs. time in tumors and liver. Measured E(FdUrd) ranged from 0.75 to 0.91 (mean 0.87 +/- 0.03) in liver and from 0.56 to 0.96 (mean 0.78 +/- 0.08) in tumors. Fluorine-18 was lost from tumors and liver at similar rates following first-pass throughput of unextracted [18F]FdUrd. Less than 10% of the radiolabel remained in tumor or liver by 3.5 hr, implying that little 18F was incorporated into long-lived molecular species within tumor or liver. The observations indicate that, in many cases, limited transport significantly reduces the flux of FdUrd into the cells of intrahepatic tumors, implying that transport must be considered in efforts to increase tumor uptake of hepatic arterially infused FdUrd.

Iododeoxyuridine uptake and retention as a measure of tumor growth.

Iodine-131-iododeoxyuridine (IUdR) uptake and retention was measured in two C6 glioma cell lines (C6m and C6a) with different growth characteristics. Animals with intracerebral (i.c.) C6a tumors had a mean survival of 16 days, whereas only 1 of 20 animals with i.c. C6m tumors died during an 8-wk period of observation. The growth of i.c. C6m tumors could be described by the Gompertz equation; tumor doubling time increased from 1.9 to 5.2 days between Days 8 and 16 after tumor inoculation. Corresponding measurements of 131I-IUdR uptake and retention (24 hr after IUdR administration) by i.c. C6m tumors were also time-dependent and decreased from 0.075 to 0.027 to 0.011 %dose/g in 8-, 10- and 16-day-old tumors, respectively. Iodine-131-IUdR uptake in "rapidly growing" i.c. C6a tumors was substantially higher (0.30 %dose/g at 24 hr) than that in "slowly growing" i.c. C6m tumors and corresponded with differences in the survival data. Subcutaneous C6a tumors had comparable high uptake values (0.49 %dose/g at 24 hr), and 93% of total tumor radioactivity was recovered in DNA 24 hr after IUdR administration. Clearance of radioactivity was rapid in nonproliferative tissues; more than 80% of plasma radioactivity was cleared in 24 hr. Tumor-to-cortex radioactivity ratios ranged from 100/1 to 120/1 and 150/1 between 24, 48 and 96 hr after IUdR injection respectively. A "washout strategy," which reduces tissue background activity and increases specificity for PET and SPECT imaging of IUdR-DNA incorporation, is possible with longer-lived radioisotopes of iodine.

The metabolic landscape of cortico-basal ganglionic degeneration: regional asymmetries studied with positron emission tomography.

Regional metabolic rate for glucose (rCMRGlc) was estimated using [18F]fluorodeoxyglucose (FDG) and positron emission tomography (PET) in five patients (four men, one woman; mean age 68; mean disease duration 2.4 years) with clinical findings consistent with the syndrome of cortico-basal ganglionic degeneration (CBGD). Left-right rCMRGlc asymmetry, (L-R)/(L + R) x 100, was calculated for 13 grey matter regions and compared with regional metabolic data from 18 normal volunteers and nine patients with asymmetrical Parkinson's disease (PD). In the CBGD group mean metabolic asymmetry values in the thalamus, inferior parietal lobule and hippocampus were greater than those measured in normal control subjects and patients with asymmetrical PD (p less than 0.02). Parietal lobe asymmetry of 5% or more was evident in all CBGD patients, whereas in PD patients and normal controls, all regional asymmetry measures were less than 5% in absolute value. Measures of frontal, parietal and hemispheric metabolic asymmetry were found to be positively correlated with asymmetries in thalamic rCMRGlc (p less than 0.05). The presence of cortico-thalamic metabolic asymmetry is consistent with the focal neuropathological changes reported in CBGD brains. Our findings suggest that metabolic asymmetries detected with FDG/PET may support a diagnosis of CBGD in life.

Abnormal cerebral glucose metabolism in long-term survivors of childhood acute lymphocytic leukemia.

Chemotherapy and radiation treatment of the central nervous system may cause delayed neurotoxicity in children with acute lymphocytic leukemia. We evaluated 12 long-term survivors of childhood leukemia using [18F]fluorodeoxyglucose positron emission tomography, computed tomography scans, clinical neurological examinations, and neuropsychological tests. Regional cerebral metabolic rate for glucose (rCMRGlc) values for white matter were lower in the older long-term survivors (greater than 18 years old) treated with cranial radiation and intrathecal chemotherapy than in normal control subjects or survivors who had been treated with intrathecal chemotherapy alone. The ratio of white matter: cortex rCMRGlc values was lower than control values in the long-term survivors treated with cranial radiation and intrathecal chemotherapy, regardless of age, but not in those treated with intrathecal chemotherapy alone. By contrast, thalamic rCMRGlc values were lower than control values in older survivors regardless of treatment, and the ratio for thalamus:cortex rCMRGlc values was lower in all the treatment groups than in the control subjects. The highest rCMRGlc values were found in the youngest children, indicating an important effect of age on cerebral glucose metabolism. No neuropsychological deficits were identified in patients treated only with intrathecal chemotherapy; however, lower IQ scores were found in the long-term survivors who had been treated with cranial radiation and intrathecal chemotherapy. Treatment of the central nervous system with cranial radiation and intrathecal chemotherapy may cause prolonged alterations in white-matter and thalamic rCMRGlc, which may permit the identification and assessment of neurotoxicity in long-term survivors of acute lymphocytic leukemia by [18F]fluorodeoxyglucose positron emission tomography.

The metabolic anatomy of Parkinson's disease: complementary [18F]fluorodeoxyglucose and [18F]fluorodopa positron emission tomographic studies.

We studied the metabolic anatomy of typical Parkinson's disease (PD) using [18F]fluorodeoxyglucose (FDG) and [18F]fluorodopa (FDOPA) and positron emission tomography (PET). Fourteen PD patients (mean age 49 years) had FDG/PET scans, of which 11 were scanned with both FDOPA and FDG. After the injection of FDOPA, brain uptake and arterial plasma radioactivity were monitored for 2 h. Striatal FDOPA uptake was analyzed with regard to a two-compartment model, and target-to-background ratios (TBRs) and TBR-versus-time slopes were also calculated. Regional patterns of metabolic covariation were extracted from FDG/PET data using the Scaled Subprofile Model (SSM). SSM pattern weights, FDOPA uptake constants (Ki), TBRs, and TBR slopes were correlated with clinical measures for bradykinesia, rigidity, tremor, gait disturbance, left-right asymmetry, dementia, and overall disease severity. In PD patients, rate constants for FDOPA uptake correlated with individual measures of bradykinesia (p = 0.001) and gait disability (p less than 0.05). SSM analysis revealed a distinct pattern of regional metabolic asymmetries, which correlated with motor asymmetries (p less than 0.001) and left-right differences in Ki (p less than 0.01). Our data suggest that in PD patients, FDG/PET and FDOPA/PET may provide unique and complementary information about underlying disease processes.

Differences in cerebral blood flow and glucose utilization in vegetative versus locked-in patients.

Positron emission tomographic studies of regional cerebral metabolic rate for glucose (rCMRGlc) and cerebral blood flow were performed in 7 vegetative and 3 locked-in patients to determine objectively the level of brain function underlying these clinical states. Cortical gray rCMRGlc in the vegetative patients was 2.73 +/- 0.13 (mean +/- SEM) mg/100 gm/min, less than half the normal value of 6.82 +/- 0.23 (p less than 0.001). Cerebral blood flow exhibited similar but more variable reductions. By contrast, cortical rCMRGlc in the locked-in patients was 5.08 +/- 0.69, a 25% reduction (p less than 0.02) from normal. The massive reduction in vegetative rCMRGlc involved not only the cerebral cortex but also the basal nuclei and cerebellum. Such metabolic hypoactivity has precedent only in deep anesthesia and supports clinical evidence that cerebral cognitive function is lost in the vegetative state, leaving a body that can no longer think or experience pain.

The metabolic pathology of the AIDS dementia complex.

A progressive dementing illness, the AIDS dementia complex (ADC) is the most frequent neurological complication of the acquired immunodeficiency syndrome. Characteristic alterations in regional cerebral metabolic rate for glucose (rCMRGlc), associated with the presence or progression of ADC, were demonstrated by [18F]fluorodeoxyglucose/positron emission tomography in 9 of 12 patients with ADC compared with 18 normal volunteer subjects. In these 9 patients, two distinct patterns of regional metabolic activity were highly correlated with intersubject gray matter rCMRGlc variation and with disease severity as assessed by neuropsychological testing. Relative subcortical (thalamus and basal ganglia) hypermetabolism was characteristic of early ADC, and disease progression was accompanied by cortical and subcortical gray matter hypometabolism.

[13N]cisplatin PET to assess pharmacokinetics of intra-arterial versus intravenous chemotherapy for malignant brain tumors.

The biodistribution, blood clearance, and in vivo transformation of cisplatin (cisdiaminedichloroplatinum, DDP) were studied in rats using 13N-labeled and unlabeled DDP. Following the i.v. injection of [13N]DDP, virtually no 13N activity was detected in brain tissue, and no measurable amount of the 13N label was displaced from [13N]DDP. Based on these results, [13N]DDP/positron emission tomographic (PET) scans were performed in two glioblastoma patients undergoing Phase II intra-arterial (i.a.) DDP chemotherapy: [13N]DDP was infused i.v. over 13-15 min, during which time serial PET scans were obtained. One hour later, [13N]DDP mixed with cold DDP (100 mg/m2 therapeutic dose) was infused at the same rate i.a., and a second sequence of PET scans was acquired. The pharmacologic advantage of i.a. administration was calculated as the ratio of integrated tumor/brain count ratios for the i.a. and i.v. studies. Our preliminary results demonstrate the feasibility of quantifying the pharmacologic advantage of i.a. DDP chemotherapy in individual brain tumor patients using [13N]DDP and PET.

Synthesis of [2-11C]5,5-dimethyl-2,4-oxazolidinedione with and without added dimethyl carbonate as a carrier for studies with positron tomography.

Two methods were developed for the synthesis of [2-11C]5,5-dimethyl-2,4-oxazolidinedione ([2-11C]DMO) for use with positron emission tomography to measure regional cerebral tissue pH in vivo in man. In both methods, A and B, [2-11C]dimethyl carbonate (DMC) was prepared from [11C]phosgene and excess of sodium methoxide in methanol containing 2-hydroxyisobutyramide (HIBA). In method A, an excess of DMC was used as a carrier, while in method B none was used. In both methods, the [2-11C]DMC solution was then heated for 10 min at 150 degrees +/- 2 degrees C causing the reaction of [2-11C]DMC with HIBA to yield [2-11C]DMO with a radiochemical purity of greater than 99%. Method A gave significantly higher radioactive yields, a pure organic product, but lower specific activities. Flash chromatography was used for the separation and purification of [2-11C]DMO prepared by method B.

Interaction of soluble pig heart glutamate-aspartate transaminase with various beta,gamma-unsaturated amino acids.

beta-Ethylidene-DL-aspartate (beta EA) and beta-methylene-DL-glutamate (beta MG) were synthesized and tested as potential suicide inhibitors of soluble pig heart glutamate-aspartate transaminase (sGAT). beta MG was found to be a) a substrate with a very low turnover number relative to glutamate and b) a competitive inhibitor with respect to aspartate (albeit with a large binding constant). At high concentrations beta MG inactivated the enzyme but only very slowly. beta EA was also found to be a substrate with a very low turnover number; it did not inactivate the enzyme (1 hr, 25 degrees C) even at a high concentration. However, beta EA was found to bind to the enzyme with an affinity comparable to that of aspartate and glutamate. beta-Methylene-DL-aspartate (beta MA) has been shown to rapidly inactivate glutamate-aspartate transaminase. Therefore, it appears that glutamate-aspartate transaminase can bind analogues of aspartate with alkene groups in the beta position. The conjugated carbonyl groups of beta MA and beta EA will enhance Michael addition in comparison with that expected for vinylglycine. On the other hand, the presence of the methyl groups should reduce the electrophilicity of the double bond of beta EA compared to beta MA. This deactivation and/or steric hindrance to Michael attack may account for the inability of beta EA to inactivate sGAT. Therefore, it may be possible to design selective suicide inhibitors of glutamate-aspartate++ transaminase with the following structure: HO2CC(= CHX)CH(CO2H)NH2, where X is an electron-withdrawing group. Ideally, X would increase the reactivity of the double bond while affording a minimum of steric hindrance to susceptible enzyme-bound bases.

In vivo measurement of brain tumor pH using [11C]DMO and positron emission tomography.

In vivo measurements of regional brain tissue/tumor pH (rpH) have been accomplished in 9 patients with primary or metastatic brain tumors using [11C]dimethyloxazolidinedione [( 11C]DMO) and positron emission tomography. Tumor rpH values ranged from 6.88 to 7.26, whereas gray matter and white matter rpH values ranged from 6.74 to 7.09 and from 6.77 to 7.03, respectively. Our results, which are consistent with reported [14C]DMO autoradiographic measurements of brain and tumor pH, suggest that the pH microenvironment of brain tumors is not more "acidic" than that of normal gray or white matter.

Intravenous self-administration of dopamine receptor agonists by rhesus monkeys.

Pharmacological studies have provided important information relevant to the behavioral role of central nervous system (CNS) dopamine (DA) as well as the existence of multiple DA receptors in the CNS. In the present experiment, the i.v. self-administration of several compounds that are direct DA receptor agonists was evaluated in rhesus monkeys. Apomorphine, piribedil, propylbutyldopamine and bromocriptine were self-administered by at least half of the animals tested, whereas SKF 38393 failed to maintain self-administration. Each of the compounds that was self-administered is an agonist at the DA2 receptor that has been demonstrated in the periphery, whereas SKF 38393 is principally a DA1 agonist. The results suggest that a DA receptor that is similar to the DA2 receptor is involved in this behavioral effect. In addition, the results are consistent with the hypothesis that CNS DA is involved in the reinforcing properties of psychomotor stimulants.

Propylbutyldopamine. Mechanism of blood pressure lowering in hypertensive patients.

The effects of propylbutyldopamine ( PBDA ), an analog of dopamine lacking significant vasoconstrictor effects, were examined in seven patients with essential hypertension. Cardiovascular hemodynamics, renal plasma flow, urinary sodium excretion, and the renin-angiotensin-aldosterone system were examined during PBDA infusion both before and after administration of low (8 micrograms/kg) and high (40 micrograms/kg) doses of the dopamine receptor antagonist metoclopramide. Infusion of PBDA at a rate of 20 micrograms/kg/min lowered mean arterial pressure from an average control value of 112 +/- 4 to 94 +/- 3 mm Hg during the last 5 minutes of infusion (p less than 0.01), and increased effective renal plasma flow from 330 +/- 22 ml/min to 591 +/- 46 ml/min (p less than 0.01). Changes in heart rate (+ 16% +/- 5% increase from control values of 77 +/- 3 bpm), urinary sodium excretion (+ 13% +/- 5% increase from control value of 121 +/- 11 muEq/min), plasma renin activity (+ 23% +/- 15% increase over control value of 1.3 +/- 0.3 ng angiotensin I/ml/hr), and plasma aldosterone (+ 26% +/- 12% increase over control value of 17 +/- 6 ng/dl) accompanied PBDA infusion. Pretreatment with metoclopramide at a dose of 8 micrograms/kg prior to PBDA infusion partially blunted the blood pressure reduction produced by PBDA alone (-10% +/- 8% vs -20% +/- 4% compared to control values, p less than 0.1) but had no effect on PBDA -induced increases in renal plasma flow (+ 179% +/- 15% vs + 179% +/- 9% compared to control).(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo measurement of regional brain tissue pH using positron emission tomography.

Carbon-11-labeled dimethyloxazolidinedione ([11C]DMO) was injected intravenously into human subjects, and serial positron emission tomographic (PET) scans were obtained until brain-blood equilibration was achieved or could be accurately predicted from dynamic PET and 11C blood data. Knowledge of regional brain-blood partition coefficients for DMO, together with measurements of arterial blood hematocrit and pH, permitted the calculation of regional brain tissue and tumor pH (rpH). [11C]DMO PET rpH values were similar to rpH values derived from quantitative autoradiographic measurements of [14C]DMO concentrations in rat brain slices.

Renal hemodynamics in hemorrhagic hypotension: studies on the effects of pre- and postjunctional dopamine receptor agonists.

The present study was conducted to determine if selective prejunctional dopamine receptor agonists will be useful in improving renal hemodynamics in acute hemorrhagic shock in anesthetized mongrel dogs. Both bromocriptine and N-n-propyl-N-n-butyl dopamine (PBDA) effectively increased renal blood flow, due to a decrease in renal vascular resistance in intact anesthetized dogs. However, these two agents failed to increase renal blood flow after acute hemorrhage in the innervated or denervated kidneys. Dopamine was effective in increasing renal blood flow in both intact and hemorrhaged animals. However, this action of dopamine in hemorrhaged animals was associated with a significant increase in arterial blood pressure. These data could be explained based on the observations that the reduction in renal blood flow following hemorrhage was primarily due to a decrease in blood pressure as a result of the decrease in cardiac output and was not due to an increase in renal vascular resistance. Because elevation of sympathetic tone appeared to play little role, prejunctional inhibition by bromocriptine and/or PBDA of sympathetic nerve function was ineffective in altering renal vascular resistance. Dopamine was effective in increasing renal blood flow, not because of its pre- or postjunctional actions on dopamine receptors on renal nerves or vasculature, but because of its ability to increase cardiac output and arterial pressure. Based on the experimental model employed in these studies, it is concluded that agents such as PBDA and bromocriptine, which are considered to be selective prejunctional dopamine agonists, may not be clinically useful in improving renal circulation during hemorrhagic shock.