A test house study of pesticides and pesticide degradation products following an indoor application.

UNLABELLED: Preexisting pesticide degradates are a concern for pesticide biomonitoring studies as exposure to them may result in overestimation of pesticide exposure. The purpose of this research was to determine whether there was significant formation and movement, of pesticide degradates over a 5-week period in a controlled indoor setting after insecticide application. Movement of the pesticides during the study was also evaluated. In a simulated crack and crevice application, commercially available formulations of fipronil, propoxur, cis/trans-permethrin, and cypermethrin were applied to a series of wooden slats affixed to the wall in one room of an unoccupied test house. Floor surface samples were collected through 35 days post-application. Concentrations of the pesticides and the following degradates were determined: 2-iso-propoxyphenol, cis/trans 3-(2,2-dichlorovinyl)-3-3-dimethyl-(1-cyclopropane) carboxylic acid, 3-phenoxybenzoic acid, fipronil sulfone, fipronil sulfide, and fipronil desulfinyl. Deltamethrin, which had never been applied, and chlorpyrifos, which had been applied several years earlier, and their degradation products, cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid, and, 3,5,6-trichloro-2-pyridinol, respectively, were also measured. Propoxur was the only insecticide with mass movement away from the application site. There was no measurable formation or movement of the degradates. However, all degradates were present at low levels in the formulated product. These results indicate longitudinal repetitive sampling of indoor degradate levels during short-term studies, is unnecessary. PRACTICAL IMPLICATIONS: Exposure to preexisting pesticide degradates may inflate estimates of exposure in biomonitoring studies where these compounds are used as biomarkers. To date, there is no published information on formation of pesticide degradates following an indoor application. We found that the study pesticides have low rates of degradation and are unlikely to be a significant factor affecting results of short-term (weeks) biomonitoring studies. Therefore, relatively few indoor samples are needed to estimate background levels of degradation products resulting from a recent pesticide application.

AAV-based gene therapy prevents neuropathology and results in normal cognitive development in the hyperargininemic mouse.

Complete arginase I deficiency is the least severe urea cycle disorder, characterized by hyperargininemia and infrequent episodes of hyperammonemia. Patients suffer from neurological impairment with cortical and pyramidal tract deterioration, spasticity, loss of ambulation and seizures, and is associated with intellectual disability. In mice, onset is heralded by weight loss beginning around day 15; gait instability follows progressing to inability to stand and development of tail tremor with seizure-like activity and death. Here we report that hyperargininemic mice treated neonatally with an adeno-associated virus (AAV)-expressing arginase and followed long-term lack any presentation consistent with brain dysfunction. Behavioral and histopathological evaluation demonstrated that treated mice are indistinguishable from littermates, and that putative compounds associated with neurotoxicity are diminished. In addition, treatment results in near complete resolution of metabolic abnormalities early in life; however, there is the development of some derangement later with decline in transgene expression. Ammonium challenging revealed that treated mice are affected by exogenous loading much greater than littermates. These results demonstrate that AAV-based therapy for hyperargininemia is effective and prevents development of neurological abnormalities and cognitive dysfunction in a mouse model of hyperargininemia; however, nitrogen challenging reveals that these mice remain impaired in the handling of waste nitrogen.

Adjunctive cognitive training with exposure enhances fear and neural outcomes in social anxiety.

Exposure-based cognitive behavioral therapy (CBT) is the gold standard for treating social anxiety disorder (SAD), yet response is not universal. CBT is thought to operate via extinction-related learning during exposure, which in turn relies on cognitive processes such as working memory. The present proof-of-concept study investigates the potential for training working memory to improve anxiety related outcomes following exposure. Thirty-three adults with elevated social anxiety were randomized to complete a working memory training or sham training condition. Post-training, participants completed a working memory assessment, speech exposure session, and two fMRI tasks. Participants who received working memory training demonstrated lower distress ratings by the end of the speech exposures and better performance on the fMRI working memory task than those in sham. Working memory training completers had greater neural activation in frontoparietal regions during an in-scanner working memory task and exhibited less neural activation in the fusiform gyrus in response to an emotional face processing task than those in sham. Adding working memory training to exposure procedures could strengthen functioning of frontoparietal regions and alter emotional processing - key mechanisms implicated in extinction learning. Findings provide preliminary evidence that training working memory in conjunction with exposure may enhance exposure success.

Performance Characteristics of BGO Detectors for a Low Cost Preclinical PET Scanner.

PETbox is a low-cost benchtop PET scanner dedicated to high throughput preclinical imaging that is currently under development at our institute. This paper presents the design and characterization of the detectors that are used in the PETbox system. In this work, bismuth germanate scintillator was used for the detector, taking advantage of its high stopping power, high photoelectric event fraction, lack of intrinsic background radiation and low cost. The detector block was segmented into a pixelated array consisting of 20 × 44 elements, with a crystal pitch of 2.2 mm and a crystal cross section of 2 mm × 2 mm. The effective area of the array was 44 mm × 96.8 mm. The array was coupled to two Hamamatsu H8500 position sensitive photomultiplier tubes, forming a flat-panel type detector head with a sensitive area large enough to cover the whole body of a typical laboratory mouse. Two such detector heads were constructed and their performance was characterized. For one detector head, the energy resolution ranged from 16.1% to 38.5% full width at half maximum (FWHM), with a mean of 20.1%; for the other detector head, the energy resolution ranged from 15.5% to 42.7% FWHM, with a mean of 19.6%. The intrinsic spatial resolution was measured to range from 1.55 mm to 2.39 mm FWHM along the detector short axis and from 1.48 mm to 2.33 mm FWHM along the detector long axis, with an average of 1.78 mm. Coincidence timing resolution for the detector pair was measured to be 4.1 ns FWHM. These measurement results show that the detectors are suitable for our specific application.

Attenuated prefrontal and temporal neural activity during working memory as a potential biomarker of suicidal ideation in veterans with PTSD.

BACKGROUND: Suicide is a significant health concern among veterans, and suicidal ideation is a common and functionally debilitating condition that frequently precedes suicidal behavior. Characterizing neurobiological substrates associated with suicidal ideation in veterans may inform evaluation of risk for this population. Associations between suicidal ideation and functional abnormalities in prefrontal, temporal, and striatal regions supporting cognitive task performance have been documented in individuals with mood and psychotic disorders, suggesting a potential role for neurocognitive vulnerabilities in this condition. To date, however, relatively little research has explored neural correlates of suicidal ideation, particularly among individuals with posttraumatic stress disorder (PTSD). METHODS: Twenty three combat veterans diagnosed with PTSD completed an adapted Reading Span (Rspan) working memory task during functional magnetic resonance imaging (fMRI). Participants were classified based on presence of current SI. We evaluated differences between these groups on neural activation in response to interference-based working memory demands within the task. Primary analyses were conducted using a voxel-wise between-group t-test. RESULTS: Task-based activations were observed in regions including the cingulate, middle frontal, parietal, and occipital cortex, striatum, and cerebellum. Relative to individuals without SI, individuals with SI demonstrated less activation in a large region spanning the lateral prefrontal cortex and cingulate cortex, as well as the inferior temporal cortex, in response to interference demands. CONCLUSIONS: Results are consistent with models proposing that prefrontal neural substrates involved in cognitive regulation are implicated in suicidal ideation. Involvement of temporal functioning may also exist based on current findings. Future research is needed to understand whether disturbances in prefrontal regulatory control reflect a specific profile subtype with distinct neural correlates, and how such neural patterns may be used to improve detection and treatment personalization.

FLT-PET imaging of radiation responses in murine tumors.

BACKGROUND: 3'-[F-18]fluoro-3'-deoxythymidine (FLT) traces thymidine phosphorylation catalyzed by thymidine kinase during cell proliferation. Knowing the rate of cell proliferation during cancer treatment, such as radiation therapy, would be valuable in assessing whether tumor recurrence is likely and might indicate the need for additional treatments. However, the relationship between FLT kinetics and the effects of radiation is not well-understood. Nor has the method for optimal quantification of FLT uptake within the irradiated tumor microenvironment been extensively examined. MATERIALS AND METHODS: We performed dynamic FLT-positron emission tomography (PET) studies (60 min) on 22 mice implanted subcutaneously with syngeneic mammary MCaK tumors bilaterally in the shoulder area. A day before the FLT-PET imaging, the tumor on the right side was irradiated with a single dose (0, 2.5, 5, 10, or 20 Gy) or with fractionated exposures (4x2.5 Gy given in 12 h intervals). Standardized uptake value (SUVs) of FLT on tumors at 10 and 60 min post injection were calculated; model fitting was used to estimate the kinetic parameters. Significant radiation-induced changes were shown by comparing the irradiated tumor with the control tumor in the same animal and by comparing it to nonirradiated mice. The effect of radiation on MCaK cell cycle parameters and FLT uptake was also examined in vitro. RESULTS: In vivo FLT kinetics were sensitive to radiation doses of 5 Gy and higher (administered 1 day earlier), as judged by SUV semiquantitative measures and by modeling. Single irradiation with 10 Gy had greater impact on SUVs and kinetic parameters than fractionated exposures. Overall, the uptake constant Ki appeared to be the best marker for these radiation effects. FLT uptake by irradiated cells in vitro at various doses gave similar findings, and the in vitro FLT uptake correlated well with Ki. Radiation-induced G2/M arrest appeared to influence FLT uptake, and this was more pronounced after single than fractionated doses. CONCLUSION: The kinetics of FLT uptake into murine mammary tumors was altered 1 day after radiation treatment. The dose-dependent response correlated well with in vitro FLT cellular uptake. Parameters (e.g., Ki) derived from FLT kinetics are expected to be useful for assessing the efficacy of irradiation treatment of tumors.

Heme enzyme patterns in rat liver nodules and tumors.

Chemically induced rat hepatocyte nodules and carcinomas have a reduced capacity to oxidize drugs. The reduction in monoxygenase activity results largely from the partial loss of cytochrome P-450, a heme-containing terminal electron acceptor. To determine whether the cytochrome P-450 deficit was indicative of an altered heme metabolism, we quantitated four heme-containing proteins in normal rat liver and in rat liver nodules and cancers induced by 2-acetylaminofluorene or diethyl-nitrosamine: cytochrome P-450; cytochrome bs; catalase (EC 1.11.1.6); and tryptophan 2,3-dioxygenase (EC 1.13.11.11). The amounts of these components in nodules were 45%, 88%, 50%, and 59% of normal liver, respectively; in 2-acetylaminofluorene-induced cancers, 65%, 74%, 64%, and 65%, respectively; and in diethylnitrosamine-induced cancers, 40%, 69%, 56%, and 52%. delta-Aminolevulinic acid synthase (EC 2.3.1.37), the rate-limiting enzyme in the heme synthetic pathway, and heme oxygenase (EC 1.14.99.3), a degradative enzyme, were also quantitated. The amounts of these enzymes in nodules were 95% and 138% of normal liver, respectively, whereas in 2-acetylaminofluorene-induced cancers, they were 47% and 233%, and in diethylnitrosamine-induced cancers, they were 50% and 175%. These data indicate that four nonmitochondrial liver hemoproteins were diminished to about the same extent in hepatic nodules and cancers. Nodules and cancers also demonstrated an increased capacity for heme degradation, while cancers also demonstrated a decreased capacity for heme synthesis. Thus, the resistance of nodules and tumors to P-450-activated cytotoxic agents may ultimately result from a disturbance in heme metabolism.

Heme enzyme patterns in genetically and chemically induced mouse liver tumors.

Chemically induced rat hepatocyte nodules and hepatomas have repeatedly been shown to be deficient in Phase I drug-metabolizing enzymes. Some of these reduced activities are attributable to a diminution of the heme-containing terminal electron acceptor, cytochrome P-450. We recently demonstrated that spontaneous mouse liver tumors exhibit the same deficiency. Therefore, chemically induced and spontaneous liver tumors share common metabolic alterations which are likely to represent intrinsic characteristics of the tumorigenic process and are independent of its etiology. To determine whether the cytochrome P-450 deficit was the result of an altered heme metabolism, we quantitated four heme-containing proteins in normal mouse liver, spontaneous mouse liver tumors, and those induced by a single injection of diethylnitrosamine: cytochrome P-450; cytochrome b5; tryptophan 2,3-dioxygenase (EC 1.13.11.11); and catalase (EC 1.11.1.6). The amounts of these components in spontaneous tumors relative to normal liver were 0.35, 0.68, 0.76, and 0.51, respectively. Similar values were obtained with chemically induced tumors. The enzymes delta-aminolevulinic acid synthase (EC 2.3.1.37), the rate-limiting enzyme in the heme synthetic pathway, and heme oxygenase (EC 1.14.99.3), a degradative enzyme, were also quantitated. The amounts of these enzymes in spontaneous tumor relative to liver were 0.49 and 1.51, respectively. Again, similar values were observed for the chemically induced tumors. Alteration of the latter two enzyme activities may be sufficient for the altered hemoprotein patterns seen in mouse liver tumors. Further, this pattern of metabolic alteration is common to both chemically induced and spontaneous tumors. Thus, tumor resistance to cytotoxic agents activated by the monooxygenase system is not necessarily induced by exposure to these agents, nor as a result of selection.

Progressive DNA damage in hepatic nodules during 2-acetylaminofluorene carcinogenesis.

The method of alkaline elution was used to detect DNA alteration in rat liver throughout the carcinogenic sequence that resulted from exposure to a standard four-cycle feeding regimen of 2-acetylaminofluorene (AFF). At the end of 3 weeks of AAF feeding, DNA from aliquots of whole liver demonstrated a small but significant degree of damage. By the end of the fourth AAF feeding, the liver exhibited numerous nodules that could be dissected free from surrounding tissue. DNA from these putative premalignant lesions showed approximately 136% more damage than that seen at the end of 3 weeks of AAF feeding. Two to 4 months following the cessation of AAF, DNA from persistent nodules was examined for eivdence of alteration. Despite the prolonged absence of exposure to AAF, DNA damage was found to have progressed and was as much as 320% greater than that seen at the end of the first cycle. While the persistence of DNA damage during chronic exposure to a carcinogen has been reported previously, the observations that the DNA of a focal lesion which is putatively premalignant was damaged and, further, that this alteration progressed in the absence of a carcinogen, are unique.

Heme synthesis in normal mouse liver and mouse liver tumors.

Hepatic cancers from mice and rats demonstrate decreased levels of delta-aminolevulinic acid synthase, the rate-limiting enzyme in the heme synthetic pathway, and increased heme oxygenase, the heme-catabolizing enzyme. These findings suggest that diminution of P-450, b5, and catalase in these lesions may result from a heme supply that is limited by decreased heme synthesis and increased heme catabolism. Heme synthesis was measured in mouse liver tumors (MLT) and adjacent tumor-free lobes (BKG) by administering the radiolabeled heme precursors 55FeCl3 and [2-14C]glycine and subsequently extracting the heme for determination of specific activity. Despite reduced delta-aminolevulinic acid synthase activity in MLT, both tissues incorporated [2-14C]glycine into heme at similar rates. At early time points, heme extracted from MLT contained less 55Fe than that from BKG. This was attributed to the findings that MLT took up 55Fe at a slower rate than BKG and had larger iron stores than BKG. The amount of heme per milligram of protein was also similar in both tissues. These findings militate against the hypothesis that diminished hemoprotein levels in MLT result from limited availability of heme. It is probable, therefore, that decreased hemoprotein levels in hepatic tumors are linked to a general program of dedifferentiation associated with the cancer phenotype. Diminution of hemoprotein in MLT may result in a relatively increased intracellular heme pool. delta-Aminolevulinic acid synthase and heme oxygenase are, respectively, negatively and positively regulated by heme. Thus, their alteration in MLT may be due to the regulatory influences of the heme pool.

Xenobiotic metabolizing enzymes in genetically and chemically initiated mouse liver tumors.

Chemically induced rat liver nodules and cancers characteristically demonstrate a limited capacity to activate xenobiotics to reactive species mainly because of decreased amounts of cytochrome P-450. These lesions also show enhancement of xenobiotic detoxication by such mechanisms as enzymic conjugation or reduction of cytotoxic species. We recently demonstrated a similar pattern of metabolic alteration in spontaneous mouse liver tumors. These findings suggested that certain phenotypic alterations attributed to chronic chemical exposure are inherent in the genetic program for carcinogenesis, and that they may arise independently of chronic exposure. To extend that study, we examined spontaneous and diethylnitrosamine-induced mouse liver tumors for nine enzyme activities commonly reported to be altered in chemically induced rat liver nodules and cancers. The activities of benzo(a)pyrene monooxygenase (EC 1.14.14.1), aminopyrene demethylase, cytochrome P-450 reductase, epoxide hydrolase (EC 3.3.2.3), and UDPglucuronosyl transferase (EC 2.4.1.17) in microsomes from spontaneous tumors relative to those from normal liver were 0.25, 0.43, 1.27, 0.90, and 0.51, respectively. Similar values were obtained with microsomes from chemically induced tumors. The activities of DT-diaphorase (EC 1.6.99.2), glutathione reductase (EC 1.6.4.2), glutathione S-transferase (EC 2.5.1.18), and glutathione peroxidase (EC 1.11.1.9) in cytosol from spontaneous tumors relative to cytosol from normal liver were 2.24, 2.0, 2.43, and 0.31, respectively. Similar values were obtained with cytosol from chemically induced tumors. These results demonstrated that a significant portion of the enzymic phenotype observed in chemically induced rat liver nodules and cancers, which may confer resistance to cytotoxic chemicals, is manifest in spontaneous and chemically induced mouse liver tumors. Further, initiated cells that exhibit this phenotype replicated and progressed in the absence of continued chemical selection.

Covalent binding of 2-acetylaminofluorene, 2-aminofluorene, and N-hydroxy-2-acetylaminofluorene to rat liver nuclear DNA and protein in vivo and in vitro.

Binding of the hepatocarcinogen 2-acetylaminofluorene (AAF) and two metabolites, 2-aminofluorene (AF) and N-hydroxy-2-acetylaminofluorene (N-OH-AAF), to the DNA and protein of rat hepatic nuclei was examined in vitro and in a cell-free system. Three and one-half hr following a single injection of each compound in equimolar amounts. DNA contained approximately 50% more of the compounds per mg than did protein. The amount of N-OH-AAF bound to DNA was 4 times greater than that of AAF, while AF bound in intermediate amounts. When incubated with nuclei in a cell-free system, AAF seldom bound in measurable amounts, while significant amounts of N-OH-AAF and AF bound to both DNA and protein. As occurred in vivo, DNA bound more of each per mg than did protein. The amount of N-OH-AFF bound to intranuclear DNA increased 54% when an aliquot of the postmicrosomal liver fraction was added to the incubation mixture, but maximum binding of AF occurred in the absence of any other liver fraction. Thus, it was shown that two AAF metabolites, AF and N-OH-AAF, bind covalently to the DNA and protein of hepatic nuclei more readily than does AAF itself and that binding in a cell-free system parallels binding in vivo. Additional evidence suggests that rat hepatic nuclei are capable of mediating the binding of AF and N-OH-AAF to macromolecules through distinct enzyme systems. This is the first demonstration that the nucleus is capable of metabolizing AF to an electrophile that can bind covalently to DNA.

Acquisition of Paleolithic toolmaking abilities involves structural remodeling to inferior frontoparietal regions.

Human ancestors first modified stones into tools 2.6 million years ago, initiating a cascading increase in technological complexity that continues today. A parallel trend of brain expansion during the Paleolithic has motivated over 100 years of theorizing linking stone toolmaking and human brain evolution, but empirical support remains limited. Our study provides the first direct experimental evidence identifying likely neuroanatomical targets of natural selection acting on toolmaking ability. Subjects received MRI and DTI scans before, during, and after a 2-year Paleolithic toolmaking training program. White matter fractional anisotropy (FA) showed changes in branches of the superior longitudinal fasciculus leading into left supramarginal gyrus, bilateral ventral precentral gyri, and right inferior frontal gyrus pars triangularis. FA increased from Scan 1-2, a period of intense training, and decreased from Scan 2-3, a period of reduced training. Voxel-based morphometry found a similar trend toward gray matter expansion in the left supramarginal gyrus from Scan 1-2 and a reversal of this effect from Scan 2-3. FA changes correlated with training hours and with motor performance, and probabilistic tractography confirmed that white matter changes projected to gray matter changes and to regions that activate during Paleolithic toolmaking. These results show that acquisition of Paleolithic toolmaking skills elicits structural remodeling of recently evolved brain regions supporting human tool use, providing a mechanistic link between stone toolmaking and human brain evolution. These regions participate not only in toolmaking, but also in other complex functions including action planning and language, in keeping with the hypothesized co-evolution of these functions.

Distribution volume of 3-O-methyl-6.

The distribution volume (DV) of 6-[F-18]fluoro-L-DOPA (FDOPA) in the cerebellum recently has been linked using positron emission tomography (PET) to plasma large neutral amino acid (LNAA) concentrations in monkeys. In this article the authors provide additional experimental support for this relation by directly measuring the DV as the steady-state tissue to plasma radioactivity ratio in rats using a labeled LNAA analog 3-O-methyl-6-[F-18]FDOPA (OMFD), a compound that has no known specific enzyme or receptor interactions in brain tissue. The measured DV for OMFD (tissue OMFD concentration/plasma OMFD concentration) was found to be inversely related to plasma LNAA concentrations. The relation (DV = 1.5-0.00094*[LNAA], R--2 = 0.79) resulted in an 8% DV decrease per 100 nmol/mL plasma LNAA increase within the observed range of 330 to 510 nmol/mL. This was similar to recent noninvasive observations with FDOPA PET in vervet monkeys and with 6-[F-18]Fluoro-m-tyrosine PET in squirrel monkeys. The OMFD striatum to cerebellum (Str/Cb) ratio was greater than 1.0 for all measurements, averaging 1.09 +/- 0.04, and was approximately equal to the Str/Cb LNAA ratio of 1.12 +/- 0.05. This current study verifies the variation of DV of OMFD or FDOPA as a function of plasma LNAA concentrations and suggests the possibility of using OMFD for measuring cerebral LNAA noninvasively with PET.

Distribution volume of radiolabeled large neutral amino acids in brain tissue.

Variations in the cerebellum to plasma ratio at late times in 6-[18F]fluoro-L-DOPA studies are shown to be consistent with competitive binding of large neutral amino acids for a common transporter in the blood-brain barrier and the stability of brain tissue large neutral amino acid level in the presence of plasma level changes. The distribution volume of an inert large neutral amino acid can be estimated from plasma and tissue large neutral amino acid levels and apparent half-saturation concentrations (Km) of the transporter in the blood-brain barrier. Stability of brain large neutral amino acid levels is supported by literature findings and can be explained by high saturation of the large neutral amino acid transporter at physiologic conditions.

Striatal kinetic modeling of FDOPA with a cerebellar-derived constraint on the distribution of volume of 30MFD: a PET investigation using non-human primates.

The peripherally born metabolite of FDOPA, 3-O-Methyl-FDOPA (3OMFD), crosses the blood-brain barrier, thus complicating positron emission tomography-FDOPA (PET-FDOPA) data analysis. In previous reports the distribution volume (DV) of 3OMFD was constrained to unity. We have recently shown that the forward transport rate-constant of FDOPA (K(S1)) and the cerebellum-to-plasma ratio (C(b)/C(p)), a measure for the DV of 3OMFD, are functions of plasma large neutral amino acid (LNAA) concentration. Given large interstudy and intersubject differences in plasma LNAA levels, variations in the DV of 3OMFD are significant. In this report, the authors propose a constraint on the DV of 3OMFD that accounts for these variations. Dynamic PET-FDOPA scans were performed on 12 squirrel monkeys and 12 vervet monkeys. Two sets of constraints were employed on the compartmental model--M1 or M2. In M1, the striatal DV of 3OMFD was constrained to unity; in M2, the striatal DV of 3OMFD was constrained to an estimate derived from the cerebellum. Striatal and cerebellar time-activity curves were fitted using FDOPA and 3OMFD plasma input functions. The estimate of K(S1) and that of the compartmental FDOPA uptake-constant (K(i)), both obtained using M2, were adjusted to values corresponding to average LNAA levels. Finally, K(i) was compared with the graphical uptake-constant (PK(j)). With the use of constraint M2, intersubject variability of squirrel monkey k(S3) and K(i) was reduced by 45% and 53%, respectively; and for vervet monkeys, by 54% and 44%, respectively. Intersubject variability of K(1) and K(i) was further reduced after correction for variations in intersubject plasma LNAA levels (for squirrel monkeys, by 67% and 41%; for vervet monkeys, by 40% and 36%, respectively). K(i) correlation to PK(i) was enhanced to identity. Finally, average cerebellar k(C2) estimates were more than 2.5-fold higher than striatal k(S2) estimates (P < 0.0001). In modeling of PET-FDOPA data, it cannot be assumed that the DV of 3OMFD is unity. The cerebellar-derived constraint furnishes a reliable estimate for the DV of 3OMFD. Invoking the constraint and correcting for variations in plasma LNAA significantly reduced interstudy and intersubject variations in parameter estimates.

Effects of large neutral amino acid concentrations on 6-[F-18]Fluoro-L-DOPA kinetics.

6-[F-18]Fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) has been used to measure the central dopaminergic function in many species, including humans and monkeys. For transport across the blood brain barrier (BBB), FDOPA competes with plasma large neutral amino acids (LNAA). In this article we evaluate the effects of normal physiological LNAA concentration variation on BBB transport (K1) and the FDOPA uptake measurement, Ki. We also investigate a method for reducing the dependency of FDOPA quantitation on LNAA. Adult vervet monkeys (Cercopithecus aethiops sabaeus, n = 19) were fasted overnight before FDOPA positron emission tomography scans. Blood samples were drawn for LNAA determination, metabolite analysis, and compartmental modeling. The estimated K1 and Ki were both negatively correlated with LNAA concentrations (r2 = 0.51 and 0.62, respectively). Using an adjustment to K1 and Ki based on these correlations, the LNAA dependency was reduced (SD of the data for K1 was reduced by 33%, for Ki by 40%). Experiments with amino acid loading on an additional six animals indicate that BBB transport can be described using Michaelis-Menten kinetics. Results show a clear dependence of FDOPA uptake on plasma LNAA concentrations, which can be removed to increase the precision of FDOPA quantitation.

Inhibition of farnesyltransferase with A-176120, a novel and potent farnesyl pyrophosphate analogue.

Farnesylation of Ras is required for its transforming activity in human cancer and the reaction is catalysed by the enzyme farnesyltransferase. Recently, we discovered a novel chemical series of potent farnesyl pyrophosphate (FPP) analogues which selectively inhibited farnesyltransferase. Our most potent compound to date in this series, A-176120, selectively inhibited farnesyltransferase activity (IC(50) 1.2+/-0.3 nM) over the closely related enzymes geranylgeranyltransferase I (GGTaseI) (IC(50) 423+/-1.8 nM), geranylgeranyltransferase II (GGTaseII) (IC(50) 3000 nM) and squalene synthase (SSase) (IC(50)>10000 nM). A-176120 inhibited ras processing in H-ras-transformed NIH3T3 cells and HCT116 K-ras-mutated cells (ED(50) 1.6 and 0.5 microM, respectively). The anti-angiogenic potential of A-176120 was demonstrated by a decrease in Ras processing, cell proliferation and capillary structure formation of human umbilical vein endothelial cells (HUVEC), and a decrease in the secretion of vascular endothelial growth factor (VEGF) from HCT116 cells. In vivo, A-176120 reduced H-ras NIH3T3 tumour growth and extended the lifespan of nude mice inoculated with H- or K-ras-transformed NIH3T3 cells. A-176120 also had an additive effect in combination with cyclophosphamide in nude mice inoculated with K-ras NIH3T3 transformed cells. Overall, our results demonstrate that A-176120 is a potent FPP mimetic with both antitumour and anti-angiogenic properties.

N-Aralkyl substitution of 2-amino-5,6- and -6,7-dihydroxy-1,2,3,4-tetrahydronaphthalenes. 2. Derivatives of a hypotensive-positive inotropic agent.

Seven derivatives of 2-[[2-(3,4-dihydroxyphenyl)-1-methylethyl]amino]-6,7-dihydroxy-1,2,3,4- tetrahydronaphthalene, an inotropic agent which also causes a decrease in blood pressure, were synthesized and tested for inotropic potency, cardioselectivity, and inotropic selectivity. The derivatives were designed to explore whether catechol moieties and rigid rotamers of dopamine are necessary for the activity which was found in the parent compound. The derivatives had phenolic functions in place of catechols, and they had phenethylamine in place of the tetrahydronaphthalene moiety. In no case was the profile of activity of the parent compound duplicated in the derivatives.

N-Aralkyl substitution of 2-amino-5,6- and -6,7-dihydroxy-1,2,3,4-tetrahydronaphthalenes. 1. Cardiac and pressor/depressor activities.

Amino substitution o rigid forms of dopamine [2-amino-5,6-dihydroxy-1,2,3,4-tetrahydronaphthalene (A-5,6-DTN) and 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (A-6,7-DTN)] with aralkyl functionalities was carried out to investigate the role of such structural modifications upon cardiac inotropic/chronotropic and blood pressure activity. Derivatives of A-5,6-DTN were strong vasodepressor agents devoid action was associated with the dihydroxyphenyl-1-methylethyl derivative, which was also an inotropic selective compound. The amino substituent of dobutamine was ineffective in reducing peripheral vascular action when combined with the rigid forms of dopamine. It was also ineffective in imparting inotropic selectivity when combined with A-5,6-DTN. An analysis of these observations in light of existing structure-activity relationships of aminoaralkyl substitution of other catecholamine structure is presented.