Usefulness of a dopamine transporter PET ligand [(18)F]beta-CFT in assessing disability in Parkinson's disease

OBJECTIVES

The usefulness of a novel dopamine transporter PET ligand, [(18)F]beta-CFT in assessing disability in Parkinson's disease was studied.

METHODS

Twenty seven patients with Parkinson's disease in different disability stages (of which nine were patients with early disease) and nine healthy controls were studied. The regions of interest were drawn on a magnetic resonance image resliced according to the PET image.

RESULTS

There was a significant reduction in [(18)F]beta-CFT uptake in the posterior putamen (to 18% of the control mean, p<0.00001), anterior putamen (28%, p<0.00001), and caudate nucleus (51%, p<0.00001) in the total population of patients with Parkinson's disease. The reduction in [(18)F]beta-CFT uptake was more pronounced with more severe disability of the patients, the correlations between the total motor score of the unified Parkinson's disease rating scale (UPDRS) and [(18)F]beta-CFT uptake being significant in the posterior putamen (r=-0.62 p=0.0005), anterior putamen (r=-0.64, p=0.0003), and the caudate nucleus (r=-0.62, p=0.0006). There was a significant negative correlation with putaminal [(18)F]beta-CFT uptake and the hypokinesia and rigidity scores, but not with the tremor score of the UPDRS motor part. In nine patients with early disease and without any antiparkinsonian medication the reduction in the [(18)F]beta-CFT uptake (average of ipsilateral and contralateral side) was reduced in the total putamen to 34% of the mean control value (p<0.00001). The corresponding figures in the other brain areas were: posterior putamen 21% (p<0.00001), anterior putamen 43% (p<0.00001), and caudate nucleus 76% (p<0.01). The reductions in [(18)F]beta-CFT uptake were more severe in the contralateral than in the ipsilateral side. Individually, [(18)F]beta-CFT uptake in the putamen in all patients was below 3 SD from the control mean.

CONCLUSIONS

[(18)F]beta-CFT is a sensitive marker of nigrostriatal dopaminergic dysfunction in Parkinson's disease and can be used in the diagnosis, assessment of disease severity, and follow up of patients.

Urodynamics changes in voiding after anti-incontinence surgery: an insight into the mechanism of cure

OBJECTIVES

To measure the effect on voiding pressure and flow rate of three different operations for stress urinary incontinence.

METHODS

In a previous study of cure rates, 289 women with genuine stress incontinence and genital prolapse were prospectively allocated in a randomized manner to one of three procedures: the Burch retropubic urethropexy, anterior repair, or the modified Pereyra procedure. In the current derivative study, we retrospectively evaluated the urodynamic indicators of voiding dysfunction in the original subjects preoperatively and at the 1-year postoperative follow-up visit.

RESULTS

One hundred thirty-two charts were available for review. One year after surgery, pressure and flow during voiding were altered to more obstructive levels with the suspension procedures (Burch and modified Pereyra). The proportion of patients with obstructive and equivocal voiding patterns after the suspension procedures was significantly greater than after anterior repair.

CONCLUSIONS

This post hoc comparison of randomized data shows a difference in postoperative voiding indexes between suspension procedures and anterior colporrhaphy. Successful bladder neck suspension depends on altering the pressure and flow during voiding to more obstructive levels. Suspension procedures alter the voiding pressure and flow toward obstruction to a greater extent than anterior repair.

Bladder neck suspension for stress urinary incontinence: how does it work?

The objective of this study was to compare urethral resistance as determined in pressure-flow studies before and after Burch retropubic urethropexy. Urethral resistance was retrospectively determined from pressure-flow studies in 178 patients before and 1 year after Burch retropubic urethropexy. Results of cotton swab tests, pressure transmission to the proximal urethra, and urethral functional length were also recorded. Results were analyzed statistically using the two-tailed paired t-test. Voiding studies in 176 patients were analyzed before and after Burch retropubic urethropexy. Mean urethral resistance increased significantly over preoperative values after successful surgery, from 0.051 to 0.099. The mean urethral resistance in patients in whom surgery failed to cure stress incontinence was unchanged from the preoperative value of 0.041. There was no direct correlation between stabilizing the bladder base, as evaluated by the cotton swab test, and cure of stress incontinence. When successful in curing genuine stress urinary incontinence, the Burch retropubic urethropexy increases urethral resistance. Creating bladder neck support without affecting urethral resistance does not, by itself, restore continence. Neurourol. Urodynam. 18:623-627, 1999.

Myocardial blood flow, oxygen consumption, and fatty acid uptake in endurance athletes during insulin stimulation

We have previously demonstrated reduced myocardial glucose uptake rates in hearts of endurance athletes, which could be due to increased use of alternative fuels or reduced energy demands. In the present study myocardial blood flow, oxygen consumption, and free fatty acid uptake were measured with [(15)O]H(2)O, [(15)O]O(2), [(18)F]FTHA, and positron emission tomography (PET) in 9 endurance athletes and 11 sedentary men during euglycemic hyperinsulinemia. Compared with sedentary men, athletes had 33% lower myocardial blood flow, 27% lower oxygen consumption, and 20% lower estimated myocardial work per gram of tissue. Myocardial fatty acid uptake rates were not significantly different in endurance athletes (0.83 +/- 0.29) and sedentary men (1.0 +/- 0.31 micromol. 100 g(-1). min(-1), P = 0.232). In conclusion, myocardial blood flow and oxygen consumption per unit mass of myocardium are reduced at rest in endurance athletes. This can be explained by reduced energy requirements per gram of tissue due to anatomic and physiological changes of the athlete's heart.

Effects of dopamine D(1-like) and D(2-like) agonists in rats that self-administer cocaine

The reinforcing effects of D(1-like) and D(2-like) agonists, and their capacity to modify cocaine self-administration, were compared in rats with extensive cocaine self-administration experience. Cocaine (0.01-1.0 mg i.v.) dose-dependently maintained responding under a fixed ratio (FR) 5 schedule of reinforcement, and an inverted U-shaped function characterized the relationship between unit dose and self-administration behavior. When substituted for cocaine, the D(1-like) agonists SKF 82958 (0.001-0.032 mg i.v.) and SKF 77434 (0.001-0.1 mg i.v.) did not maintain responding above levels observed during saline substitution. In contrast, the D(2-like) agonists quinelorane (0.001-0.1 mg i.v.) and 7-hydroxy-dipropylaminotetralin (7-OH-DPAT; 0.01-0.32 mg i.v.) reliably maintained i.v. self-administration behavior that was characterized by inverted U-shaped dose-effect functions. Pretreatment with the D(1-like) agonists SKF 82958 and SKF 77434 (0.1-1.0 mg/kg i.p.) shifted the dose-effect function for cocaine self-administration downward, whereas pretreatment with the D(2-like) agonists quinelorane (0.01 mg/kg i.p.) and 7-OH-DPAT (0.32-1.0 mg/kg i.p.) shifted the cocaine dose-effect function to the left. Effects of D(1-like) and D(2-like) agonists on patterns of responding maintained by cocaine (0.32 mg i.v.) also differed: D(1-like) agonists increased the latency to the first response but did not otherwise alter patterns of cocaine self-administration, whereas D(2-like) agonists increased the intervals between self-administered cocaine injections. The results suggest that D(2-like) agonists, but not D(1-like) agonists, have prominent reinforcing effects and enhance the effects of self-administered cocaine in rats with extensive cocaine self-administration experience. Consequently, D(2) receptor-related neuronal mechanisms may be especially important in mediating the abuse-related effects of cocaine.

Protection against 12-O-tetradecanoylphorbol-13-acetate induced skin-hyperplasia and tumor promotion, in a two-stage carcinogenesis mouse model, by the 2,3-dimethyl-6(2-dimethylaminoethyl)-6H-indolo-[2,3-b]quinoxaline analogue of ellipticine

The effects of topical applications of 2,3-dimethyl-6(2-dimethylaminoethyl)-6H-indolo-[2,3-b]quinoxaline (B-220), on 12-O-tetradecanoylphorbol-13-acetate (TPA) or benzoylperoxide (BPO) induced promotion of skin tumors and hyperplasia were studied in female SENCAR mice. Papillomas were induced by initiation with 7,12-dimethylbenz[a]anthracene (DMBA), followed by promotion biweekly with TPA or BPO. Administration of B-220 1 h before TPA promotion resulted in a prolonged latency period of tumor appearance and a significantly reduced (up to 15% of positive controls) papilloma yield at 20 weeks. Moreover, if B-220 treatment was terminated after 20 weeks and TPA treatment continued, papilloma development resumed indicating that initiated tumor cells were still present but were unable to grow with B-220 present. If B-220 pretreatment was not given during the first 10 weeks of TPA promotion, incidence at 20 weeks was not reduced but tumor multiplicity was still decreased. In addition a marked reduction of the TPA induced sustained epidermal hyperplasia was observed in the long term experiment. Neither the inflammatory response nor the increase in the number of apoptotic cells seen in short term experiment after a single TPA treatment were inhibited by B-220. B-220 administration before BPO promotion had no effect on the appearance of BPO induced papillomas or epidermal hyperplasia, suggesting that TPA and BPO promote tumor formation via at least partially different mechanisms. In experiments where B-220 was applied topically 1 h before DMBA initiation, little or no effect was seen. No morphological changes in mouse skin due to long term exposure (two times/week, 39 weeks) to B-220 were found. In conclusion, we present evidence that B-220 is a potent inhibitor of mouse skin tumor promotion by TPA, but has little effect on the initiation step or the survival of initiated cells.

Apparent pA2 values of benzodiazepine antagonists and partial agonists in monkeys

Drugs that bind to benzodiazepine recognition sites of gamma-aminobutyric acid type A receptor complexes may function as agonists in some behavioral assays and as antagonists in other behavioral assays. The present studies compared the effects of the benzodiazepines midazolam, flumazenil, bretazenil, Ro 41-7812, and Ro 42-8773 and the beta-carboline, beta-carboline-3-carboxylate-t-butyl ester (beta-CCt) under two different types of schedule-controlled responding in squirrel monkeys. One group of monkeys responded under a fixed-ratio schedule of stimulus-shock termination, and a second group of monkeys responded under a multiple fixed-ratio schedule of food presentation involving suppressed and nonsuppressed behavior. Under the schedule of stimulus-shock termination, midazolam produced dose-related decreases in response rate, and these effects were surmountably antagonized by flumazenil, bretazenil, Ro 41-7812, Ro 42-8773, and beta-CCt. Schild plot analysis of these data revealed the following mean pA(2) values: flumazenil, 7.18; bretazenil, 7.62; Ro 41-7812, 7. 06; Ro 42-8773, 6.95. Apparent pA(2) values were not calculated for beta-CCt because the CL of the slope of the Schild plot included positive values. Under the multiple schedule, midazolam, bretazenil, and Ro 42-8773 dose-dependently increased rates of suppressed responding, whereas flumazenil, Ro 41-7812, and beta-CCt had no significant rate-altering effects. Flumazenil antagonized the antisuppressant effects of midazolam and bretazenil; however, individual variability in these effects prohibited the determination of apparent pA(2) values. These results indicate that in vivo pA(2) values may be determined for benzodiazepine-site ligands. These results further demonstrate that some benzodiazepine-site ligands, e. g., bretazenil and Ro 42-8773, may function as both agonists and as competitive antagonists in vivo.

Anxious attachment and severity of depressive symptomatology in women

The present research evaluated a conceptual model that links anxious attachment to depressive symptomatology in women. Four hundred and twenty women completed the following measures: Socio-demographic questionnaire, the Centre for Epidemiological Studies Depression Scale (CES-D), the Reciprocal Attachment Questionnaire, the Social Support Questionnaire, the Rosenberg Self-Esteem Scale and the Global Assessment of Recent Stress Scale. Results indicate that feared loss of the attachment figure, intense proximity seeking and lack of use of the attachment figure were predictive of depressive symptomatology. We also found that lower levels of self-esteem and higher levels of recent stress were predictive of depressive symptomatology. The implications of these findings for the understanding of symptoms of depression in women is discussed.

Cerebral blood flow and glucose metabolism in long-term survivors of childhood acute lymphoblastic leukaemia

Central nervous system treatment for childhood acute lymphoblastic leukaemia (ALL) has been reported to cause changes in cerebral blood flow and glucose metabolism. Little is known about the association of these functional changes with neuropsychological defects and structural changes. The aim of the present study was to assess the relationship between changes in regional cerebral blood flow and glucose utilisation in long-term survivors of ALL, and the association of these functional abnormalities with neurocognitive and structural defects. 8 survivors of childhood ALL were studied with single photon emission tomography (SPECT) using Tc99m-ethyl cysteinate dimer (ECD) as tracer and with positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) as tracer. 8 healthy controls also underwent FDG-PET. All subjects also underwent magnetic resonance imaging and neuropsychological assessment 5 years after cessation of the therapy. Focal cerebral blood flow abnormalities were found in ECD-SPECT in 5 of the 8 survivors. Glucose utilisation appeared normal in the corresponding regions. However, glucose utilisation was decreased in thalamus and cerebellum in the survivors of ALL as compared with healthy controls. 3 patients had severe and 5 patients mild neurocognitive difficulties. The changes in cerebral blood flow and FDG uptake did not correspond neuroanatomically with the neurocognitive defects. Focal defects in cerebral blood flow in long-term survivors of ALL are not associated with changes in local cerebral glucose utilisation. Neurocognitive difficulties are not consistently associated with either changes in cerebral blood flow or with decreased glucose utilisation. Therefore, based on the present set of studies FDG-PET and ECD-SPECT cannot yet be recommended for the evaluation of long-term neurocognitive defects associated with treatment of ALL.

[18F]FDG-PET and whole-scalp MEG localization of epileptogenic cortex

PURPOSE

To evaluate combined [18F]fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) and 122-channel whole-scalp magnetoencephalography (MEG) in lateralizing the epileptogenic cortex in patients whose routine presurgical evaluations gave discordant results about the location of the epileptic focus.

METHODS

Nine patients (five women, four men) aged 13-40 years were studied. Subdural EEG (SEEG) was recorded from eight patients. Six patients were operated on.

RESULTS

In seven of nine patients, PET and MEG agreed in localizing the epileptogenic cortex. When PET and MEG were in congruence, SEEG agreed with the findings. In five of six operated-on patients, PET and MEG results were congruent, and the outcome of the operation was successful. Two patients had discordant PET and MEG results. In one patient, PET showed bitemporal hypometabolism, whereas MEG showed epileptiform activity in the right parietal lobe. The surgical outcome of the palliative temporal lobectomy was poor. Another patient had unilateral temporal hypometabolism in PET and bitemporal activity in MEG. She was not operated on.

CONCLUSIONS

In most patients, PET and MEG were congruent in locating the epileptogenic cortex. Thus the combination of these techniques may provide useful support for the localization of the seizure onset and reduce the need for invasive procedures.

The synthetic non-toxic drug 2,3-dimethyl-6(2-dimethylaminoethyl)-6H-indolo-(2,3-b)quinoxaline inhibits neutrophil production of reactive oxygen species

The effects of the non-toxic drug 2,3-dimethyl-6(2-dimethylaminoethyl)-6H-indolo-(2,3-b)quinoxaline (B220) on the generation of reactive oxygen species froin human neutrophils were investigated. The data show that B220 inhibits neutrophil release of reactive oxygen species, as well as intracellular generation of reactive oxygen species. The inhibition is not achieved through direct oxygen radical scavenger activity of B220, and the drug has no immediate effects on the activity of the assembled oxidase. Radical production and release were inhibited by all agonists tested [i.e. the protein kinase C-activating phorbol ester phobol myristate acetate; the receptor-specific agonist N-formyl-methionyl-leucyl-phenylalanine (fMLP); and serum-opsonized yeast particles] in the presence of B220. The drug also inhibits phagocytosis and fMLP-induced mobilization of granules. However, based on the fact that the effects of B220 on phagocytosis and granule mobilization are much less significant than its effect on radical production, we suggest that the signal(s) affected by B220 is (are) located mainly downstream of the point at which the signals are generated to promote oxidase activation and phagocytosis or granule secretion, respectively.

Impaired free fatty acid uptake in skeletal muscle but not in myocardium in patients with impaired glucose tolerance: studies with PET and 14(R,S)-[18F]fluoro-6-thia-heptadecanoic acid

Free fatty acids (FFAs) are an important substrate for myocardial and skeletal muscle metabolism, and increased availability and oxidation of FFA are suggested to be associated with insulin resistance. This study was undertaken to assess whether myocardial or muscle uptake of FFA is altered in patients with impaired glucose tolerance (IGT). Eight healthy men (control group; age 48+/-1 years, BMI 25+/-1 kg/m2, mean +/- SE) and eight men with IGT (glucose-intolerant group; age 49+/-1 years, BMI 29+/-1 kg/m2) were studied in the fasting state. Myocardial oxygen consumption and blood flow and myocardial and femoral muscle FFA uptake rates were measured with positron emission tomography (PET) and [15O]O2, [15O]H2O, [15O]CO, and 14(R, S)-[18F]fluoro-6-thia-heptadecanoic acid ([18F]FTHA), a fatty acid tracer trapped into the cell after undergoing initial steps of beta-oxidation. Serum glucose and insulin concentrations were higher in the glucose-intolerant group during the PET study, but FFA concentrations were comparable between the groups. No differences between the groups were observed in the myocardial blood flow, oxygen consumption, fractional FTHA uptake rates, or FFA uptake indices (5.6+/-0.4 vs. 5.2+/-0.4 pmol x 100 g(-1) x min(-1), glucose-intolerant versus control, NS). In the femoral muscle, fractional FTHA uptake (0.0062+/-0.0003 vs. 0.0072+/-0.0003 min(-1), P = 0.044) and FFA uptake indices (0.30+/-0.02 vs. 0.43+/-0.04 min(-1), P = 0.020) were significantly lower in the glucose-intolerant group than in the control group. In conclusion, when studied at the fasting state and normal serum FFA concentrations, subjects with IGT have similar myocardial but lowered femoral muscle FFA uptake. This finding argues against the hypothesis that an increased oxidation of serum FFA, via the competition of glucose and FFA as fuel sources, is the primary cause for impaired peripheral glucose utilization and insulin resistance commonly observed in IGT.

Uncoupling of fatty acid and glucose metabolism in malignant lymphoma: a PET study

Increased use of glucose through glycolysis is characteristic for neoplastic growth while the significance of serum-free fatty acids for regulation of energy metabolism in cancer is poorly understood. We studied whether serum-free fatty acids (FFA) interfere with glycolytic metabolism of lymphoproliferative neoplasms as assessed with 2-F18-fluoro-2-deoxy-D-glucose ([F18]FDG) and positron emission tomography (PET). Twelve patients with newly diagnosed non-Hodgkin's lymphoma (n = 9) or Hodgkin's disease (n = 3) participated in this study before start of oncologic treatment. Each patient underwent two [F18]FDG PET studies within 1 week after overnight fast: once during high fasting serum FFA concentrations and once after reduction of serum FFA by administration of acipimox. Acipimox is a nicotinic acid derivative that inhibits lipolysis in peripheral tissues and induces a striking reduction in circulating FFA concentration. In all cases, dynamic PET imaging over the tumour area was performed for 60 min after injection of [F18]FDG. Both graphical analysis (rMR(FDG)) and single scan approach (SUV) were used to compare tumour uptake of [F18]FDG under high fasting FFA concentrations and after pharmacologically decreased FFA concentrations. Serum FFA concentrations were reduced significantly from 0.92+/-0.42 mmol I(-1)at baseline to 0.26+/-0.31 mmol I(-1) after acipimox administration (P = 0.0003). Plasma glucose, serum insulin and lactate concentrations were similar during both approaches. The retention of glucose analogue [F18]FDG in tumour was similar between baseline and acipimox studies. Median rMR(FDG) of a total of 12 involved lymph nodes in 12 patients was 21.9 micromol 100 g(-1) min(-1) (range 8.7-82.5) at baseline and 20.1 micromol 100 g(-1) min(-1)(range 10.7-81.7) after acipimox. The respective values for median SUV were 7.8 (range 3.6-18.6) and 6.0 (range 4.1-20.2). As expected, [F18]FDG uptake in myocardium was clearly enhanced by acipimox due to reduction of circulating FFAs. In conclusion, blood fatty acids appear to have minor significance for [F18]FDG uptake in lymphoma. This suggests that glucose utilization is uncoupled of FFA metabolism and indicates that glucose-free fatty acid cycle does not operate in lymphomatous tissue. Glucose appears to be the preferred substrate for energy metabolism in tumours, in spite of the high supply of FFAs in the fasting state. Although acipimox and other anti-lipolytic drugs have potential for treatment of catabolic state induced by cancer, they are not likely to interfere with tumour energy metabolism which is fuelled by glucose.

Striatal uptake of a novel PET ligand, [18F]beta-CFT, is reduced in early Parkinson's disease

[18F] beta-CFT is a novel PET ligand for dopamine reuptake sites. In this study, [18F]beta-CFT uptake was studied in nine patients with early Parkinson's disease (PD) without antiparkinsonian medication and in six age-matched controls. The uptake of [18F]beta-CFT was calculated as a (region-cerebellum)/cerebellum ratio at 150-210 min after injection. The mean uptake in the putamen contralateral to the predominant symptoms (1.04+/-0.40, mean +/- SD; P<0.001) was reduced to 31% of the mean control value. In the "ipsilateral" putamen, the ratio in PD patients (1.50+/-0.50, P<0.001) was reduced to 45% of the control mean (3.33+/-0.61). Individually, all PD patients had [18F]beta-CFT uptake values below 2 SD from the control mean in the contralateral putamen. The decline in [18F]beta-CFT uptake in the caudate nucleus was milder than that seen in the putamen. The uptake was reduced contralaterally (2.19+/-0.47, P<0.01) to 67% and ipsilaterally (2.49+/-0.54, P<0.05) to 77% of the control mean (3.17+/-0.61). In the medial frontal cortex or dorsolateral prefrontal cortex, no significant difference in [18F]beta-CFT uptake between patients and controls was seen. In conclusion, [18F]beta-CFT is a powerful ligand to demonstrate presynaptic dopaminergic defect in PD and shows a clear separation of patient and control values.

Depressive symptoms and presynaptic dopamine function in neuroleptic-naive schizophrenia

We have previously reported aberrations in the striatal presynaptic dopamine function in neuroleptic-naive schizophrenic patients compared to healthy controls (Hietala, J., Syvälahti, E., Vuorio, K. et al., 1995. Lancet 346, 1130-1131). In this extended study we explore whether the altered presynaptic dopamine function correlates with the clinical symptomatology in schizophrenia. Striatal dopamine synthesis capacity (6-[18F]fluorodopa (FDOPA) uptake, Ki values) was studied with positron emission tomography in 10 neuroleptic-naive schizophrenic patients and 13 healthy controls. The clinical symptomatology was characterized with the Positive and Negative Symptom Scale (PANSS). The patients had an increased FDOPA uptake in striatum and lacked the asymmetry in caudate FDOPA uptake (p = 0.0005), confirming our earlier results. Left striatal FDOPA uptake (Ki) values correlated negatively with depressive symptoms in a highly significant manner. On the other hand, paranoid symptomatology correlated positively with right putamen FDOPA uptake at a trend level (rho = 0.73, p < 0.02). The lack of asymmetry in caudate Ki values did not associate with any dimension of psychopathology. The major finding in this study is that depressive symptoms in neuroleptic-naive first-admission schizophrenia are associated with low presynaptic dopamine function. This link appears to be hemisphere-related and may have drug-treatment implications, e.g., in prediction of response to D2 receptor blocking antipsychotic drugs. A possible connection between paranoid symptomatology and subcortical hyperdopaminergia is suggested, but this remains to be further verified.

Increased brain glucose utilization in Salla disease (free sialic acid storage disorder)

Salla disease is an autosomal recessive lysosomal free sialic acid storage disorder characterized by psychomotor retardation and ataxia. MRI studies have revealed evidence of dysmyelination, but the biological mechanism of the brain dysfunction is unknown.

METHODS

Nine patients with Salla disease (age 2.5 mo-42 y) presenting the disease in varying degrees of severity were studied by PET using 2-fluoro-2-deoxy-D-glucose (FDG) as a tracer. Local cerebral metabolic rates for glucose (LCMRGlc) in individual brain regions were compared with controls.

RESULTS

The FDG PET results showed significantly increased LCMRGlc values in the frontal and sensorimotor cortex and especially in the basal ganglia of the patients. Cerebellar hypometabolism was present in all seven patients with marked ataxia, whereas the less severely affected patients without obvious ataxia had normal or even high glucose uptake in the cerebellum.

CONCLUSION

The increased cerebral glucose utilization is a constant finding in Salla disease and may reflect the basic defect of the sialic acid metabolism in this disorder. The FDG PET findings in the cerebellum suggest a correlation between glucose uptake and the severity of the clinical symptoms.

A longitudinal study of positive symptoms in schizo-affective and paranoid schizophrenia

The purpose of our work was studying the evolution of positive psychopathological symptoms in patients who had suffered from schizo-affective (N=146) and paranoid schizophrenia (N=74) (according to ICD-9CM) for at least 5 years. Using the list of syndromes taken from the Present State Examination, we retrospectively analyzed 2118 relapses registered in these patients' life during their illness (mean 18.1 years). According to our data, when the course of schizo-affective and paranoid schizophrenia incorporates definite periods of remission, there is a tendency towards a simplification of positive symptoms: 1.for 26.4% of the patients, the illness manifested itself in infrequent relapses (once in 4-5 years or less); 2. in 45.9% of the patients (those who displayed prominent regressive tendencies) psychotic symptoms were replaced by symptoms of affective, primarily depressive, type; 3. in 18.6% of the patients the illness took the form of recurring uniform attacks; 4. only in a mere 9.1% of the patients was the disorder diagnosed as progressive; and 5. a tendency to improvement and favorable prognosis was more pronounced in schizo-affective schizophrenia patients than in patients with paranoid schizophrenia (69.9% vs 54.1%, P<0.05).

Promethazine overdose: is it a "Goodnight" after all?

AIMS

To evaluate and describe the perceived increase in number of promethazine overdoses presenting to Auckland Hospital Emergency Department since Goodnight became available in New Zealand.

METHOD

Emergency Department records were reviewed for 19.5 months from 19 December 1994 (when Goodnight became available on the New Zealand market) until 31 July 1996. The Emergency Department database for the preceding years dating back to 1 January 1984 was reviewed.

RESULTS

There were a total of 25 patients (18 female; 7 male) with 17 patients being between the ages of 15-25. The first cases presented in April 1995 and 15 cases (60%) presented during the 1996 period of the study. Fifteen patients (60%) ingested one or more full boxes of Goodnight. Twelve patients (48%) were admitted to intensive care, eight of whom were intubated. Fifteen patients were discharged from hospital in under 24 hours, but five (20%) stayed 2-3 days. Records dating back to 1 January 1984 revealed a total of 31 cases of promethazine overdose in just under 11 years, nine being accidental ingestion in children less than 5 years of age.

CONCLUSIONS

This review highlights the high morbidity and cost of having promethazine available as an unrestricted, pharmacy--only medication. It suggests that marketing laws should be reviewed and the availability of promethazine be curtailed.

Drug discrimination in methamphetamine-trained monkeys: agonist and antagonist effects of dopaminergic drugs

The involvement of D1 and D2 subtypes of dopamine receptors in behavioral effects of methamphetamine was studied in squirrel monkeys using a two-lever drug discrimination procedure. In monkeys that discriminated i.m. injections of 0.3 mg/kg methamphetamine from saline, methamphetamine (0.03-0.3 mg/kg), cocaine (0.1-1.0 mg/kg) and the selective dopamine uptake inhibitor, GBR 12909 (3.0-17.8 mg/kg) produced dose-related increases in responding on the methamphetamine-associated lever and, at the highest doses, full substitution. In contrast, the norepinephrine and serotonin uptake inhibitors, tomoxetine (1.0-17.8 mg/kg) and fluoxetine (0.3-10.0 mg/kg), respectively, did not substitute appreciably for methamphetamine. Substitution for methamphetamine also was observed with the D1 receptor agonists, SKF 81297, SKF 82958 and dihydrexidine, and the D2 receptor agonist, (+)-PHNO in the majority of monkeys. Lower-efficacy D1 or D2 agonists substituted for methamphetamine either partially (SDZ 208-911) or not at all (SKF 77434, SDZ 208-912). Pretreatment with dopamine receptor blockers [D1 (SCH 39166, 0.1 mg/kg) or D2 (remoxipride, 3.0 mg/kg and nemonapride, 0.003 mg/kg)] and low-efficacy agonists [D1 (SKF 77434; 3.0 mg/kg) or D2 (SDZ 208-911 and SDZ 208-912; 0.01-0.03 mg/kg)] antagonized the discriminative-stimulus effects of methamphetamine. In separate studies, comparable doses of each of these drugs, except SKF 77434, induced significant levels of catalepsy-associated behavior. These results support the view that both dopaminergic D1 and D2 mechanisms mediate the discriminative-stimulus effects of methamphetamine; further, they indicate that selected dopamine D1 partial agonists may have antagonist actions at doses that do not produce undesirable effects associated with dopamine receptor blockade.

Interactions of the antiviral quinoxaline derivative 9-OH-B220 [2, 3-dimethyl-6-(dimethylaminoethyl)- 9-hydroxy-6H-indolo-[2, 3-b]quinoxaline] with duplex and triplex forms of synthetic DNA and RNA

The binding of an antiviral quinoxaline derivative, 2,3-dimethyl- 6 - (dimethylaminoethyl) - 9 - hydroxy - 6H - indolo - [2,3 - b]quinoxaline (9-OH-B220), to synthetic double and triple helical DNA (poly(dA).poly(dT) and poly(dA).2poly(dT)) and RNA (poly(rA). poly(rU) and poly (rA).2poly(rU)) has been characterized using flow linear dichroism (LD), circular dichroism (CD), fluorescence spectroscopy, and thermal denaturation. When either of the DNA structures or the RNA duplex serve as host polymers a strongly negative LD is displayed, consistent with intercalation of the chromophoric ring system between the base-pairs/triplets of the nucleic acid structures. Evidence for this geometry also includes weak induced CD signals and strong increments of the fluorescence emission intensities upon binding of the drug to each of these polymer structures. In agreement with intercalative binding, 9-OH-B220 is found to effectively enhance the thermal stability of both the double and triple helical states of DNA as well as the RNA duplex. In the case of poly(dA).2poly(dT), the drug provides an unusually large stabilization of its triple helical state; upon binding of 9-OH-B220 the triplex-to-duplex equilibrium is shifted towards higher temperature by 52.5 deg. C in a 10 mM sodium cacodylate buffer (pH 7.0) containing 100 mM NaCl and 1 mM EDTA. When triplex RNA serves as host structure, LD indicates that the average orientation angle between the drug chromophore plane and the helix axis of the triple helical RNA is only about 60 to 65 degrees. Moreover, the thermal stabilizing capability, as well as the fluorescence increment, CD inducing power and perturbations of the absorption envelope, of 9-OH-B220 in complex with the RNA triplex are all less pronounced than those observed for the complexes with DNA and duplex RNA. These features indicate binding of 9-OH-B220 in the wide and shallow minor groove of poly(rA).2poly(rU). Based on the present results, some implications for the applications of this low-toxic, antiviral and easily administered drug in an antigene strategy, as well as its potential use as an antiretroviral agent, are discussed.

[18F]CFT [(18F)WIN 35,428], a radioligand to study the dopamine transporter with PET: characterization in human subjects

We have characterized the usage of [18F]CFT (also known as [18F]WIN 35,428) as a radioligand for in vivo studies of human dopamine transporter by PET. CFT was labeled with 18F to a high specific activity, and dynamic PET scans were conducted in healthy volunteers at various time points up to 5 h from [18F]CFT injection. The regional distribution of [18F]CFT uptake correlated well with the known distribution of dopaminergic nerve terminals in the human brain and also with that of other dopamine transporter radioligands. Striatal binding peaked at 225 min after injection and declined thereafter, demonstrating the reversible nature of the binding to the dopamine transporter. Therefore, due to the relatively long half-life of 18F (109.8 min), PET scans with [18F]CFT could easily be conducted during the binding equilibrium, allowing estimation of Bmax/Kd values (i.e., binding potential). Binding potentials for putamen and caudate measured at equilibrium were 4.79+/-0.11 and 4.50+/-0.23, respectively. We were able to also visualize midbrain dopaminergic neurons (substantia nigra) with [18F]CFT in some subjects. In conclusion, the labeling of CFT with 18F allows PET scans to be conducted at binding equilibrium, and therefore a high signal-to-noise ratio and reliable quantification of binding potential can be achieved. With a high resolution 3D PET scanner, the quantification of extrastriatal dopamine transporters should become possible.

Striatal presynaptic dopamine function in type 1 alcoholics measured with positron emission tomography

Recent in vivo studies have shown low dopamine D2 receptor and dopamine transporter densities among late onset (type 1) alcoholics. We have now studied 6-[18F]-FDOPA (FDOPA) uptake in 10 type 1 alcoholics and eight matched controls to test the hypothesis that striatal presynaptic dopamine function is lower among alcoholics. Markedly low FDOPA uptake (Ki) was observed in the left caudate of two alcoholic patients, but the mean striatal uptake values of the patient group were higher than those of the control group. The greatest difference was observed in the mean FDOPA intake in the left putamen, which was 28% higher in the patient group (t = 3.00, P = 0.008, d.f. = 16, independent samples t-test), and in the right caudate (difference 36%, t = 2.87, P = 0.01). The elevated FDOPA uptake in putamen and caudate correlated with poor Wisconsin Card Sorting Test (WCST) performance (error %) among alcoholics (correlation coefficients from 0.49 to 0.56), which suggests that the magnitude of presynaptic dopamine function alteration correlates with the degree of disability to modify one's behavior. The results do not give support to the hypothesis of generally decreased striatal dopamine turnover in type 1 alcoholism, but on the contrary indicate an increased presynaptic dopamine function. This may represent a compensatory mechanism to low postsynaptic DA function. The low presynaptic DA function observed in the left caudate of two patients suggests that type 1 alcoholism may be a heterogeneous disorder.

Long-term outcome of autoimmune disease following allogeneic bone marrow transplantation

OBJECTIVE

To investigate the long-term outcome of autoimmune disease following allogeneic bone marrow transplantation (BMT), and its relationship to hemopoietic chimerism.

METHODS

Three previously described patients with rheumatoid arthritis (RA) who underwent allogeneic BMT for therapy-related severe aplastic anemia and 1 new patient with psoriasis who received BMT for chronic myeloid leukemia (CML) were followed up. Molecular studies were performed to assess hemopoietic and immune reconstitution in 3 cases.

RESULTS

In 2 of the RA patients, the RA remained in remission without treatment, with nonprogressive disease, 11 and 13 years after BMT. The third patient with RA had a relapse 2 years after BMT, although the previously aggressive disease subsequently ran an attenuated course with treatment-free remission for the last 11 years. Comparison with other cases of RA suggests that graft-versus-host disease may influence the long-term outcome, perhaps through ongoing inhibition of the immune system. In the patient with psoriasis, BMT was followed by remission, but the psoriatic rash recurred and arthropathy developed 12 months later. The psoriasis and arthropathy remained active 4.5 years post-BMT, although the CML remained in remission. Molecular studies in the 2 patients whose RA remained in continued remission and in the patient with psoriasis that relapsed confirmed complete donor hemopoietic reconstitution.

CONCLUSION

Long-term followup of autoimmune disease after allogeneic transplantation confirmed cure of the autoimmune disease in some, but eventual relapse in others. The occurrence of relapse despite complete donor hemopoietic reconstitution is evidence for the development of de novo, as opposed to persistent, disease, and is possibly related to intrinsic susceptibility of the transplanted stem cells or to host factors. There may be a relationship between remission of autoimmune disease and graft-versus-host reaction. These findings have relevance for the evolving application of stem cell transplantation as a therapy for autoimmune diseases.

Comparison of [18F]FDG-PET, [99mTc]-HMPAO-SPECT, and [123I]-iomazenil-SPECT in localising the epileptogenic cortex

OBJECTIVES

Firstly, to compare the findings of interictal 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and of single photon emission computed tomography (SPECT) using 99mTc-hexamethyl propylene-amine-oxime (HMPAO) and 123I-iomazenil in localising the epileptogenic cortex in patients who were candidates for epilepsy surgery, but in whom clinical findings, video EEG monitoring (V-EEG), MRI, and neuropsychological evaluations did not give any definite localisation of the seizure onset. Secondly, to assess the ability of these functional methods to help in the decision about the epilepsy surgery.

METHODS

Eighteen epileptic patients were studied with FDG-PET and iomazenil-SPECT. HMPAO-SPECT was performed in 11 of these 18 patients. Two references for localisation was used--ictal subdural EEG recordings (S-EEG) and the operated region.

RESULTS

Fifteen of 18 patients had localising findings in S-EEG. FDG-PET findings were in accordance with the references in 13 patients and iomazenil-SPECT in nine patients. HMPAO-SPECT visualised the focus less accurately than the two other methods. In three patients S-EEG showed independent bitemporal seizure onset. In these patients FDG-PET showed no lateralisation. However, iomazenil-SPECT showed temporal lobe lateralisation in two of them.

CONCLUSION

FDG-PET seemed to localise the epileptogenic cortex more accurately than interictal iomazenil-SPECT in patients with complicated focal epilepsy.

Prediction of survival with fluorine-18-fluoro-deoxyglucose and PET in head and neck cancer

The aim of this prospective study was to investigate if high uptake of 18F-fluoro-2-deoxy-D-glucose (FDG) is associated with aggressiveness in head and neck cancer and low probability of survival.

METHODS

Thirty-seven patients with squamous-cell carcinoma of the head and neck underwent FDG-PET in the fasting state before cancer treatment. FDG uptake in primary tumor was quantitated as the standardized uptake value of FDG normalized to the predicted lean body mass (SUVlean, n = 37) and as the graphically determined metabolic rate for FDG (rMR[FDG], n = 34). Paraffin-embedded tumor samples were used for histologic evaluation, and expression of cytokeratin and Ki-67 antigen were assessed by immunohistochemistry.

RESULTS

Interobserver agreement for the determination of quantitative uptake of FDG in tumors was excellent (r2 = 0.996, p < 0.00001), and all 37 primary tumors were visualized. A high uptake of FDG as assessed by SUVlean was associated with a higher than the median mitotic count (p = 0.01), absence of keratinization (p = 0.03), low or moderate histological grade of differentiation (p = 0.046) and advanced stage (p = 0.03), but not with Ki-67 expression (p = 0.11). The overall survival of patients with a SUVlean lower than or equal to the median value (9.0) was clearly better in univariate analysis than that of patients with a SUVlean higher than the median (3-yr survival 73% versus 22%, relative risk of death (RR) 4.2, 1.6-11.0). However, in a multivariate analysis the only independent predictors of survival were the mitotic count (RR 4.0, 1.4-11.7) and stage (3.8, 1.2-12.2).

CONCLUSION

High uptake of FDG in untreated head and neck cancer is associated with advanced disease, and may portend poor survival. Aggressive treatment approaches should be considered for patients presenting with a tumor with high uptake of FDG.

Microsatellites of the parasitic nematode Haemonchus contortus: polymorphism and linkage with a direct repeat

To develop tools to analyse parasitic nematode population structures and the effects of selection pressure on the nematode population, we isolated and characterised 13 microsatellite markers of the nematode Haemonchus contortus. The density of CA/GT microsatellites, once in 575 kb, is lower than in mammals. Although the isolated CA/GT repeats were imperfect, the majority of the microsatellites were polymorphic in one or more populations. An extensive genetic diversity both within and between populations could be established. Two-thirds of the CA/GT microsatellites were followed by a variable number of 128 bp direct repeat elements, HcREP1. HcREP1 is a repetitive element in the H. contortus genome, which is homologous to the repetitive TcREP element in the nematode Trichostrongylus colubriformis.

Differential modulation of behavioral effects of cocaine by low- and high-efficacy D1 agonists

Dopamine D1 agonists differing in efficacy with respect to stimulation of adenylate cyclase activity and other in vitro and in vivo criteria were evaluated for their capacity to modulate the behavioral effects of cocaine in squirrel monkeys. Monkeys were trained either to respond on a fixed-ratio schedule in which lever pressing terminated a stimulus associated with electric shock or to discriminate cocaine from vehicle using a two-lever drug-discrimination procedure. When administered in combination with cocaine, D1 agonists displaying relatively low efficacy (SKF 38393, SKF 75670) attenuated both the rate-altering effects of cocaine on fixed-ratio responding and the discriminative-stimulus effects of cocaine, resulting in overall rightward shifts of the cocaine dose-response functions. Maximal attenuation of the behavioral effects of cocaine by the D1 partial agonists was comparable to that produced by the D1 antagonist SCH 39166. In contrast, D1 agonists displaying relatively high efficacy (SKF 81297, SKF 82958, SKF 83189) either had little effect on or accentuated the rate-altering and discriminative-stimulus effects of cocaine. The results show that D1 partial agonists can act as functional cocaine antagonists and may be viable candidate medications for the management of cocaine addiction.

Fluorine-18-labeled fluorine gas for synthesis of tracer molecules

The aim of this work was to develop a method to produce 18F-labeled fluorine gas ([18F]F2) with high specific radioactivity (SA, radioactivity/mass-ratio). 18F-Labeled methyl fluoride ([18F]CH3F) was synthesized from [18F]F-aq and mixed with carrier F2 in an inert neon matrix. The constituents were atomized in an electric discharge, after which a rearrangement and 18F for 19F exchange took place. [18F]F2 with a specific radioactivity of up to 55 GBq/mumol is available for the labeling synthesis of tracers for positron emission tomography (PET).

JL13, a pyridobenzoxazepine compound with potential atypical antipsychotic activity: a review of its behavioural properties

The search for an improved clozapine-like compound has resulted in the selection of a new molecule: JL13 (5-(4-methylpiperazin-1-yl)-8-chloro-pyrido[2,3-b][1,5] benzoxazepine fumarate). Like clozapine, JL13 did not antagonize apomorphine-induced stereotypy and did not produce catalepsy but antagonized apomorphine-induced climbing in rodents (ID50 = 3.9 mg kg-1 s.c.). It was inactive against d-amphetamine-induced stereotypy but antagonized d-amphetamine-induced hyperactivity in the mouse (ID50 = 4.4 mg kg-1 i.p.). JL13, like clozapine, was able to antagonize (+/-)-DOI-induced head-twitches in the mouse (ID50 = 2.0 mg kg-1 i.p.). In the open-field test in the rat and forced swimming test in the mouse a high similarity was noted between the two drugs in the same range of doses. In a complex temporal regulation schedule in the dog, JL13 showed a high resemblance with clozapine without inducing sialorrhea, palpebral ptosis or any significant motor side effects. In rats trained to discriminate clozapine, JL13 (10 mg kg-1 i.p.) induced a high level of generalization (70%) to clozapine. In a drug discrimination procedure in the squirrel monkey, JL13 (3-10 mg kg-1 i.m.) produced a full substitution of clozapine. On the basis of these preclinical data, it is thus predicted that JL13 would be a promising atypical antipsychotic drug.

Discriminative-stimulus effects of clozapine in squirrel monkeys: comparison with conventional and novel antipsychotic drugs

The effects of conventional and novel atypical antipsychotic drugs were compared to clozapine in squirrel monkeys that discriminated I.M. injections of clozapine (1.0 mg/kg) from saline in a two-lever drug discrimination procedure. Clozapine (0.03-3.0 mg/kg) produced dose-related increases in responding on the clozapine-associated lever with full substitution at the training dose in all monkeys. Dose-related increases in responding on the clozapine-associated lever and full substitution also were observed with structural analogues of clozapine including perlapine and fluperlapine (0.1-3.0 mg/kg), seroquel (0.1-5.6 mg/kg), and JL 5, JL 8 and JL 18 (0.1-3.0 mg/kg). Other clozapine analogues, including olanzapine, amoxapine, loxapine and clothiapine, and conventional antipsychotic drugs, including phenothiazines such as chlorpromazine and thioridazine, produced some clozapine-associated responding up to the highest doses that could be studied, but did not substitute for clozapine. Olanzapine did produce full clozapine-lever responding following pretreatment with the dopamine D2-receptor agonist (+)-PHNO (0.003-0.01 mg/kg). Putatively atypical antipsychotics that are structurally unrelated to clozapine including risperidone (0.003-0.1 mg/kg), sertindole (0.03-1.0 mg/kg) and remoxipride (0.1-5.6 mg/kg) similarly failed to substitute for clozapine up to the highest doses. The present results indicate that some, but not all, structural analogs of clozapine have clozapine-like discriminative-stimulus effects and that novel antipsychotic drugs which purportedly have clozapine-like clinical efficacy may not produce its interoceptive stimulus effects.

Cerebral metabolic rate for glucose after neonatal hypoglycaemia

OBJECTIVE

We studied the effect of neonatal hypoglycaemia on the local cerebral metabolic rate for glucose (LCMRglc).

MATERIALS AND METHODS

Eight newborn infants with neonatal hypoglycaemia were studied. The LCMRglc in the whole brain, in five cerebral regions and in skeletal muscles were quantitated using positron emission tomography (PET) and 2-[18F]Fluoro-2-deoxy-D-glucose (FDG). The PET studies were performed at the age of 5.3 +/- 6.2 days during normoglycaemia. The LCMRglc of these infants were compared to the age-adjusted LCMRglc of eight infants with suspected hypoxic-ischaemic brain injury but with normal neurological development.

RESULTS

After neonatal hypoglycaemia the age-adjusted LCMRglc in the whole brain was not lower than LCMRglc of the control infants (5.33 +/- 0.60 mumol/100 g/min vs. 6.71 +/- 0.60 mumol/100 g/min). Also the metabolic rate for glucose (MRglc) in the skeletal muscles was similar in hypoglycaemic and control infants (5.56 +/- 2.48 mumol/100 g/min vs. 6.99 +/- 2.41 mumol/100 g/min).

CONCLUSION

MRglc in brain and in skeletal muscle seems to be normal after neonatal hypoglycaemia, although larger group of patients with more severe hypoglycaemia are needed to confirm this finding.

[18F]fluorodopa PET shows striatal dopaminergic dysfunction in juvenile neuronal ceroid lipofuscinosis

OBJECTIVES

To investigate whether nigrostriatal dopaminergic hypofunction is related to the extrapyramidal symptoms in patients with juvenile neuronal ceroid lipofuscinosis (JNCL).

METHODS

Nine patients with JNCL and seven healthy controls were studied using [18F]fluorodopa PET.

RESULTS

In the patients with JNCL [18F]fluorodopa uptake (K[i][occ]) in the putamen was 60% of the control mean and the corresponding figure in the caudate nucleus was 79%. There was a weak correlation between putamen K(i)(occ) values and extrapyramidal symptoms of the patients evaluated by the motor part of the unified Parkinson's disease rating scale (r = -0.57, P < 0.05). The overall severity of the disease also displayed a negative correlation with the K(i)(occ) values in the putamen (r = -0.71, P < 0.05).

CONCLUSION

In patients with JNCL there was reduced striatal [18F]fluorodopa uptake, which had a modest correlation with extrapyramidal symptoms. Dysfunction of nigrostriatal dopaminergic neurons is therefore not the only cause of the patients' extrapyramidal symptoms, but degenerative changes in other brain areas are also contributory.

Regulation of dioxin receptor function by omeprazole

The intracellular dioxin (aryl hydrocarbon) receptor mediates signal transduction by dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin) and related environmental pollutants and functions as a ligand-activated transcription factor. In this study we have examined the effects on dioxin receptor function of a potentially novel ligand, omeprazole, which is widely clinically used as a gastric anti-ulcer drug. In primary human hepatocytes omeprazole potently induced cytochrome P4501A1 mRNA expression, whereas this effect was not detected in mouse primary hepatocytes. In human hepatoma cells omeprazole was found to induce transcription of reporter genes via the xenobiotic response element that is recognized by the ligand-activated dioxin receptor. In contrast, the human dioxin receptor was not activated by omeprazole upon expression in a receptor-deficient mouse hepatoma cell line. In a reconstituted yeast (Saccharomyces cerevisiae) model system, however, both the mouse and human dioxin receptors were potently activated by omeprazole. Although omeprazole failed to displace dioxin in in vitro ligand binding assays, a residue within the ligand binding domain that is critical for dioxin binding in vitro was also critical for omeprazole responsiveness in vivo. Consistent with this observation, both omeprazole and dioxin responsiveness of the dioxin receptor was inhibited in mutant yeast cells expressing low levels of the molecular chaperone hsp90 that is critical for ligand binding activity. The sulfoxide group that is essential for formation of a planar conversion product of omeprazole was found to be critical for dioxin receptor activation. Taken together, these data suggest that omeprazole represents a precursor for a novel class of dioxin receptor agonists that are bona fide dioxin receptor ligands but generated in a strictly species-specific manner.

Preneoplastic lesions, DNA adduct formation and mutagenicity of 5-, 7- and 9-hydroxy-2-nitrofluorene, metabolites of the air pollutant 2-nitrofluorene

The metabolites of 2-nitrofluorene (NF), 5-, 7- and 9-OH-2-nitrofluorene (OH-NF) were compared for their genotoxicity. Seventy-two hours after intraperitoneal administration of these substances individually to rats (100 mg/kg body wt.), DNA adducts in liver tissue were analyzed with 32P-TLC and 32P-HPLC. An in vivo liver model was used to test the initiating capacity of the said substances for the formation of preneoplastic lesions. 5-OH-NF showed low capacity to induce DNA adduct formation and low potential as initiator to induce preneoplastic lesions-foci/nodules in the liver of rats. Both 7- and 9-OH-NF induced DNA adducts and preneoplastic liver lesions but with smaller quantities compared to NF. It seems that 7- and 9-OH-NF can not be considered as detoxification products of NF. In general, the initiating capacity of these substances for the formation of preneoplastic lesions has a good correlation with their potency to form DNA adducts.

[18F]CFT ([18F]WIN 35,428), a radioligand to study the dopamine transporter with PET: biodistribution in rats

We describe the 18F-radiolabelling synthesis (18F; T(1/2) = 109.8 min) of 2-beta-carbomethoxy-3 beta-(4-fluorophenyl)tropane (also known as CFT or WIN 35,428) and the biodistribution of this compound in rats. 18F-labelled CFT has high chemical and radiochemical purity and relatively high specific radioactivity [specific radioactivity up to 14.8 GBq/mumol (400 mCi/mumol) at end of synthesis]. Striatum to cerebellum radioactivity uptake ratios were calculated from digitised images of rat brain slices recorded with a phosphoimaging device, the maximum ratio of about 10 was obtained at 2 h postinjection. Pretreatment of the rats with a specific dopamine transport inhibitor, GBR 12909, showed that CFT binding is specific in striatum. The highest accumulation of 18F-radioactivity was found in the liver, urine, striatum, and kidney of the rat. Clearance from blood was rapid. The uptake in bone was low, indicating that [18F]CFT is not defluorinated. The relatively long half-life of 18F makes it possible to study the uptake of [18F]CFT in the brain, as equilibrium between specific and non-specific binding is reached. This will improve the signal to noise ratio as compared to positron emission tomography (PET) studies with [11C]CFT (11C; T(1/2) = 20.4 min). CFT labelled with 18F is clearly a promising radioligand for PET studies of the dopamine transporter system in humans.

Serotonergic modulation of striatal D2 dopamine receptor binding in humans measured with positron emission tomography

The modulating effect of serotonergic drugs on the striatal dopamine neurotransmission has remained controversial, and there are no published data on serotonin-dopamine interaction obtained from living human brain. Citalopram is a selective serotonin reuptake inhibitor widely used in the treatment of depression (20-40 mg/day). We measured the effects of acute (20 mg, per os) and chronic (20 mg/day for 14 days) doses of citalopram and placebo intake on [11C]-raclopride binding to striatal D2-receptors in eight healthy volunteers by using positron emission tomography. Although the effect magnitude was not large, the results indicate that chronic citalopram intake slightly decreases the raclopride binding which may reflect increased dopamine release in the striatum. In addition, after 14 days there was a high correlation between the citalopam plasma levels and the decrease in the [11C]-raclopride binding in both the caudate and the putamen, although statistically significant effect in the raclopride binding potential was more pronounced in the putamen. This report suggests functional interaction of brain dopaminergic and serotonergic systems in vivo in man.

CT, MRI, and PET in a case of intractable epilepsy

We report the case of a child with drug-refractory partial epilepsy in whom computed tomography showed no abnormality and magnetic resonance imaging showed a noninvasive cystic lesion in the left hippocampus. The finding in the positron emission tomography study with L-[methyl-11C]-methionine as a tracer suggested a tumor. This finding was confirmed histologically.

Self-administration of D1 receptor agonists by squirrel monkeys

Dopaminergic mechanisms are believed to play a prominent role in the self-administration of cocaine and other abused stimulants. The contribution of D2 receptors is now well established, but less is known about the role of D1 receptors in the reinforcing effects of these drugs. To help clarify the role of D1 mechanisms in stimulant self-administration, agonists differing in D1 receptor selectivity (SKF 81297 > SKF 82958 > SKF 77434) and efficacy (SKF 82958 > SKF 81297 > SKF 77434) were studied for their ability to maintain IV self-administration in squirrel monkeys previously trained to self-administer cocaine. Up to a 100-fold range of doses of each D1 agonist was studied under both a fixed-ratio (FR) and a second-order fixed-interval (FI) schedule of reinforcement. Parallel studies were conducted with the D2 receptor agonists, (+)-PHNO and quinpirole, under the second-order FI schedule. Of the three D1 agonists, only SKF 82958 maintained consistent self-administration under both the FR and second-order FI schedules and had dose-related effects that were qualitatively similar to those of (+)-PHNO and quinpirole under the latter condition. SKF 81297, which has high selectivity at D1 receptors and intermediate agonist efficacy, maintained self-administration in the majority of monkeys under the FR schedule, but did not maintain self-administration under the second-order FI schedule. SKF 77434, which has moderate selectivity at D1 receptors and low agonist efficacy, did not maintain self-administration under either schedule. The results suggest that the ability of D1 agonists to maintain IV self-administration in squirrel monkeys depends both on the type of schedule and on the pharmacological properties (i.e. selectivity and efficacy) of the particular drug. These results are also consistent with the view that D1, in addition to D2, receptor mechanisms play a role in the self-administration of abused stimulants.

Cerebral metabolic rate for glucose during the first six months of life: an FDG positron emission tomography study

AIM

To measure the local cerebral metabolic rate for glucose (LCMRGlc) in neonatal brains during maturation using positron emission tomography (PET) and 2-[18F]fluoro-2-deoxy-D-glucose (FDG).

METHODS

Twenty infants were studied using PET during the neonatal period. The postconceptional age ranged from 32.7 to 60.3 weeks. All infants had normal neurodevelopment and were normoglycaemic. The development of the infants was carefully evaluated (follow up 12-36 months) clinically, and by using a method based on Gesell Amatruda's developmental diagnosis. LCMRGlc was quantitated using PET derived from FDG kinetics and calculated in the whole brain and for regional brain structures.

RESULTS

LCMRGlc for various cortical brain regions and the basal ganglia was low at birth (from 4 to 16 mumol/100 g/minute). In infants 2 months of age and younger LCMRGlc was highest in the sensorimotor cortex, thalamus, and brain stem. By 5 months, LCMRGlc had increased in the frontal, parietal, temporal, occipital and cerebellar cortical regions. In general, the whole brain LCMRGlc correlated with postconceptional age (r = 0.90; P < 0.001). The change in the glucose metabolic pattern observed in the neonatal brain reflects the functional maturation of these brain regions.

CONCLUSION

These findings show that LCMRGlc in infants increases with maturation. Accordingly, when LCMRGlc is measured during infancy, the postconceptional age has to be taken into account when interpretating the results.

Respiratory effects of opioid full and partial agonists in rhesus monkeys

Respiratory and behavioral effects of the mu selective opioids levorphanol (0.01-3.0 mg/kg), methadone (0.03-5.6 mg/kg) and codeine (0.3-30.0 mg/kg) and the mixed-action opioids buprenorphine (0.003-10.0 mg/kg), butorphanol (0.003-0.3 mg/ kg) and nalbuphine (0.03-30.0 mg/kg) were studied in rhesus monkeys. In respiratory experiments, awake, seated monkeys wore plastic masks through which they breathed air or differing concentrations of CO2 mixed in air. Exposure to CO2 in air stimulated ventilation in a concentration-dependent manner. All opioids produced dose-dependent decreases in ventilation that were more pronounced as the concentration of CO2 increased. The highest doses of levorphanol, methadone, and butorphanol reduced the ventilatory stimulant effects of 5% CO2 in air by 85 to 90%, whereas the highest doses of nalbuphine, buprenorphine and codeine reduced the effects of 5% CO2 in air by only 50 to 75%. After presession butorphanol (0.01-0.1 mg/kg) or nalbuphine (1.0-3.0 mg/kg), levorphanol further reduced the ventilatory stimulant effects of 5% CO2 mixed in air, with some evidence of dose-effect flattening. However, pretreatment with buprenorphine (1.0-10.0 mg/kg) and the highest dose of nalbuphine (10.0 mg/kg) attenuated the effects of 10.0 mg/kg levorphanol, indicative of antagonism. In behavioral experiments, all drugs produced dose-related decreases in responding under a 30-response fixed-ratio schedule. The highest doses of levorphanol, methadone, codeine, and butorphanol nearly abolished responding in all subjects, whereas buprenorphine and nalbuphine most often reduced response rates by no more than 50%. Except for codeine, rank orders of potency were the same in behavioral and respiratory experiments. The lesser effects of nalbuphine and buprenorphine on ventilation, in conjunction with their levorphanol-antagonist effects, suggest their limited mu agonist efficacy at sites mediating the respiratory-depressant effects of opioids.

Agonist efficacy and the behavioral effects of dopamine D1 receptor ligands: drug interaction studies in squirrel monkeys

Dopamine agonists that reportedly differ in intrinsic activity at dopamine D1 receptors were compared for their behavioral effects in squirrel monkeys responding under a fixed-ration schedule of reinforcement. When administered alone, all drugs produced dose-related decreases in fixed-ratio response rates. Pretreatment with the dopamine D1 receptor blocker SCH 39166, but not the dopamine D2 receptor blocker eticlopride, produced rightward shifts in the dose-effect functions for the high-efficacy dopamine D1 agonists SKF 82958 (R,S-6-chloro-7,8-dihydroxy-3-allyl-1-phenyl-2,3,4,5-tetrahydro- 1H-3-benzazepine) SKF 81297 (R,S-6-chloro-7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine ) and dihydrexidine, indicative of surmountable antagonism at dopamine D1 receptors. Pretreatment with SCH 39166, however, did not antagonize the effects of the low-efficacy dopamine D1 agonists SKF 75670 (R,S-7,8-dihydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine ), SKF 77434 (R,S-7,8-dihydroxy-3-allyl-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine) or R-SKF 38393 (R-7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine); instead, dose-effect functions for each of these drugs were shifted downward and to the left. In additional experiments, pretreatment with SKF 75670 produced overall rightward shifts in the dose-effect functions for dihydrexidine and SKF 81297; pretreatment with R-SKF 38393 produced an overall rightward shift in the dose-effect function for dihydrexidine, but not SKF 81297; and pretreatment with SKF 81297 failed to produce a rightward shift in the dose-effect function for dihydrexidine. These findings provide further evidence that the behavioral effects of dopamine D1 agonists in monkeys are mediated primarily by their actions at dopamine D1 receptors. The differing susceptibility of dopamine D1 agonists to antagonism by SCH 39166 and their differing interactions provide functional evidence for differences in their dopamine D1 agonist efficacy.

Naloxonazine antagonism of levorphanol-induced antinociception and respiratory depression in rhesus monkeys

The mu-opioid receptor antagonist effects of naloxonazine on levorphanol-induced thermal antinociception and respiratory depression were examined in rhesus monkeys. Levorphanol (0.032-3.2 mg/kg) produced dose-dependent increases in tail-withdrawal latencies from 50 degrees C water in a warm-water tail-withdrawal assay and dose-dependent decreases in ventilation in both air and 5% CO2 mixed in air. Naloxonazine (0.1-3.0 mg/kg) antagonized both the antinociceptive and ventilatory effects of levorphanol to a similar degree, and the antagonist effects of naloxonazine were greater after 1 h than after 24 h. Under all conditions, the antagonist effects of naloxonazine were fully surmountable. Schild analysis of the antagonist effects of naloxonazine after 1 h pretreatment in the antinociception assay yielded a pA2 value of 7.6 and a slope of -0.50; by comparison, quadazocine yielded a pA2 value of 7.5 and a slope of -1.05. These results suggest that naloxonazine acts as a potent and fully reversible mu-opioid receptor antagonist with a moderately long duration of action in rhesus monkeys. In addition, these results suggest that the antinociceptive and ventilatory effects of mu-opioid receptor agonists in rhesus monkeys are mediated by pharmacologically similar populations of mu opioid receptors.

Estimated radiation dose to the newborn in FDG-PET studies

The aim of this study was to estimate the radiation dose due to intravenous injection of 2-[18F]fluoro-2-deoxy-D-glucose (FDG) for infants studied with PET.

METHODS

The radioactivity concentration in the brain and bladder content was measured with PET to determine the cumulated activity in these organs in 21 infant FDG studies. The individual organ masses were estimated according to the whole-body and brain masses, and they were used to calculate the absorbed dose per unit cumulated activity (S values). For organs other than brain and bladder, the cumulated activity was defined from adult studies. For each individual patient, the absorbed dose to the brain, bladder wall and selected organs were calculated. An estimation of the effective dose was determined.

RESULTS

Whole-body distribution of FDG in the infants differed from adults: a greater proportion of the injected activity accumulated into the brain (9% versus 7%) and less was excreted to urine (7% versus 20% respectively). The measured cumulated activity in the brain was 0.25 MBq.h/MBq and in the bladder content 0.04 MBq.h/MBq with a large individual variation in latter. The calculated absorbed dose was 0.24 mGy/MBq to the brain and 1.03 mGy/MBq to the bladder wall. The estimated effective dose was 0.43 mSv/MBq.

CONCLUSION

The dose to the bladder wall was lower in infants as compared to adults with ordinary amounts of injected activity. The greater amount of activity remaining in the body may increase the dose to other organs. The effective dose was lower compared to adults and conventional nuclear medicine studies of infants. PET can be a valuable tool in pediatric nuclear medicine because of good resolution images, sensitive radiation measurement and a variety of tracers labeled with short-lived isotopes.