Neurological complications from cocaine use are well recognized. We propose that chronic cocaine use can also cause clinically silent brain dysfunction. We investigated brain glucose metabolism with ...positron emission tomography (PET) and 2-deoxy-218F fluoro-D-glucose (FDG) in 21 neurologically intact chronic cocaine abusers (C) and 18 normal controls (N). The cocaine abusers were tested 1-6 weeks after the last use of cocaine and seven were retested after a 3 month drug-free period. Global cerebral glucose metabolism was not significantly different between controls and cocaine abusers (N = 38.4 +/- 3, C = 36.5 +/- 5 mumol/100 g of tissue, min). However, cocaine abusers had significantly (P less than 0.05) lower metabolic activity in 16 of the 21 left frontal regions and 8 of the 21 right frontal regions. These decreases persisted after 3-4 months of detoxification and were correlated with the dose (P less than or equal to 0.01) and the years of cocaine use (P less than or equal to 0.05). This study shows reduced rates of frontal metabolism in neurologically intact cocaine abusers that persist even after 3-4 months of detoxification.
The rate of low birth weight (LBW) of Black women is more than twice that of White women. This study explores if the rate of LBW differs between Haitian and African-American women with chronic ...hypertension.
A retrospective cohort study of all Black women self-identified as African-American (n = 12,258) or Haitian (n = 4320) delivering a singleton infant in Massachusetts between 1996 and 2000.
Haitian women were more likely than African-American women to have chronic hypertension (2.7% vs. 2.1%, p = 0.006), but had similar rates of preeclampsia (3.1% vs. 3.3%, p = 0.27). The LBW rate was 10% among African-American women and 8.2% among Haitian women. After adjustment for sociodemographic, medical, and prenatal care characteristics, the greatest risks for delivering a LBW infant for Haitian women were chronic hypertension (OR = 6.8; 95% CI, 4.3, 10.6) and preeclampsia (OR = 3.2; 95% CI, 2.0, 5.1). For African-American women, the greatest risks for LBW infants were a history of delivering a LBW infant (OR = 3.9; 95% CI, 2.8, 5.4) and chronic hypertension (OR = 2.9; 95% CI, 2.1, 4.0). In a combined logistic regression model including interaction terms, chronic hypertension and preeclampsia continued to be associated with the greatest risk of LBW among all women.
Differences in maternal risk factors and rates of LBW (8.2% vs. 10%) exist between Haitian and African-American women delivering infants in Massachusetts. While chronic hypertension and preeclampsia are strong risk factors for LBW for both Haitian and African-American women, unknown factors make these disorders much more potent for Haitian women.
Although treatment with zidovudine significantly reduces the likelihood of mother-to-infant transmission of the human immunodeficiency virus (HIV),
1
perinatally acquired infections still account for ...the majority of new cases of the acquired immunodeficiency syndrome (AIDS) in children.
2
,
3
Zidovudine has been the recommended treatment for these children, but controlled trials have not been conducted to compare it with other antiretroviral agents or combination therapies in children. Recent studies in adults suggest that combination antiretroviral regimens, particularly those including protease inhibitors, may prolong the period of HIV nonprogression,
4
but comparable studies have not been done in children. In this study, we compared . . .
Abstract Variation in the monoamine-oxidase-A (MAO-A) gene has been associated with volumetric changes in corticolimbic regions with differences in their response to relevant emotional tasks. Here we ...show no changes in baseline regional brain metabolism as a function of genotype indicating that, unchallenged, corticolimbic activity is not modulated by the MAO-A genotype.
A cut-and-paste approach using a family of structurally similar ‘growth patches’, and starting from a 24-vertex fullerene ‘seed’, allows formal construction of all fullerene isomers with up to at ...least 200 atoms.
A cut-and-paste approach using a family of structurally similar ‘growth patches’ (pairs of non-isomorphic patches with the same boundary but containing different numbers of vertices) allows formal construction from a C
24 seed of all fullerene isomers with up to at least 200 atoms. Algorithmic and chemical implications are discussed.
L-Deprenyl (Selegeline) is an enzyme-activated irreversible inhibitor of monoamine oxidase B (MAO B; EC 1.4.3.4). It is used to treat Parkinson's disease at a dose of 5 mg twice a day. Since enzyme ...inhibition is irreversible, the recovery of functional enzyme activity after withdrawal from L-deprenyl requires the synthesis of new enzyme. We have measured a 40 day half-time for brain MAO B synthesis in Parkinson's disease and in normal subjects after withdrawal from L-deprenyl. This is the first measurement of the synthesis rate of a specific protein in the living human brain. L-Deprenyl is currently used by 50,000 patients with Parkinson's disease in the United States and its use is expected to increase with reports that it may be beneficial in Alzheimer's disease. The slow turnover of brain MAO B suggests that the current clinical dose of L-deprenyl may be excessive and that the clinical efficacy of reduced dosing should be evaluated. Such an evaluation may have mechanistic importance as well as an impact on reducing the side effects and the costs arising from excessive drug use.
In this letter, we have investigated the effects of incorporating a thin silicon layer into a SiO2-based resistive switching random access memory. The thin silicon layer was deposited onto the ...sidewall region of the device by physical vapor deposition. It is found that this thin silicon layer effectively reduces the electroforming voltage and stabilizes device current in both low- and high-resistance programmed states. It is concluded that the improved performance is due to formation of a more robust, more uniform conducting filament. As a result of this advantage, stable tri-state programming can be achieved in the SiO2-based resistive memory device.
The purpose of this study was to assess the reproducibility of repeated positron emission tomography (PET) measures of brain monoamine oxidase B (MAO B) using deuterium-substituted
11CL-deprenyl (
...11CL-deprenyl-D2) in normal subjects and to validate the method used for estimating the kinetic constants from the irreversible 3-compartment model applied to the tracer binding. Five normal healthy subjects (age range 23–73 years) each received two PET scans with
11CL-deprenyl-D2. The time interval between scans was 7–27 days. Time-activity data from eight regions of interest and an arterial plasma input function was used to calculate λ
k
3, a model term proportional to MAO B, and
K
1, the plasma to brain transfer constant that is related to blood flow. Linear (LIN) and nonlinear least-squares (NLLSQ) estimation methods were used to calculate the optimum model constants. A comparison of time-activity curves for scan 1 and scan 2 showed that the percent of change for peak uptake varied from −18.5 to 15.0% and that increases and decreases in uptake on scan 2 were associated with increases and decreases in the value of the arterial input of the tracer. Calculation of λ
k
3 showed a difference between scan 1 and scan 2 in the global value ranging between −6.97 and 4.5% (average −2.1 ± 4.7%). The average percent change for eight brain regions for the five subjects was −2.84 ± 7.07%. Values of λ
k
3 for scan 1 and scan 2 were highly correlated (r
2 = 0.98;
p < 0.0001; slope 0.955). Similarly, values of
K
1 showed a significant correlation between scan 1 and scan 2 (r
2 = 0.61;
p < 0.0001; slope 0.638) though the values for scan 2 were generally lower than those of scan 1. There was essentially no difference between the values of model constants calculated using the NLLSQ or LIN methods. Regional brain uptake of
11CL-deprenyl-D2 varied between scan 1 and scan 2, driven by the differences in arterial tracer input. Application of a 3-compartment model to regional time-activity data and arterial input function yielded λ
k
3 values for scan 1 and scan 2 with an average difference of −2.84 ± 7.07%. Linear regression applied to values of λ
k
3 from the LIN and NLLSQ methods validated the use of the linear method for calculating λ
k
3.
This paper considers the problem of locating closely-spaced coherent emitters. Classical TDOA-based emitter location methods assume only a single emitter is being estimated. As a result, when ...multiple emitters that cannot be resolved during detection exist, the MSE performance is significantly degraded. These errors are due to the fact that the TDOA observation model does not account for multiple transmissions. We propose a new TDOA observation model that can resolve multiple emitted signals. We show a significant improvement in MSE when locating multiple emitters using our new model as compared with the classical one-emitter assumption TDOA model.
The reinforcing effects of cocaine and methylphenidate have been linked to their ability to block dopamine transporters (DAT). Using positron emission tomography (PET), we previously showed that ...intravenous cocaine induced a significant level of DAT blockade, which was associated with the intensity for self-reports of "high" in cocaine abusers. In this study, we measured DAT occupancies after intravenous methylphenidate and assessed whether they also were associated with the "high". Occupation of DAT by intravenous MP was measured with PET using 11Ccocaine, as a DAT ligand, in eight normal control subjects tested with different methylphenidate doses. The ratio of the distribution volume of 11Ccocaine in striatum to that in cerebellum, which corresponds to Bmax/Kd + 1, was used as measure of DAT availability. In parallel, self-reports of "high" were measured. Methylphenidate produced a dose-dependent blockade of DAT with an estimated ED50 of 0.075 mg/kg. DAT occupancies were significantly correlated with the "high" (p <.03). However, four of the eight subjects, despite having significant levels of DAT blockade, did not perceive the "high". Methylphenidate is as effective as cocaine in blocking DAT in the human brain (cocaine ED50 = 0.13 mg/kg), and DAT blockade, as for cocaine, was also associated with the "high". However, the fact that there were subjects who despite significant DAT blockade did not experience the "high" suggests that DAT blockade, although necessary, is not sufficient to produce the "high".
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