Comparison of high specific activity (-) and (+)-6-[18F]fluoronorepinephrine and 6-[18F]fluorodopamine in baboons: heart uptake, metabolism and the effect of desipramine

(-)-Norepinephrine is the principal neurotransmitter of the mammalian sympathetic nervous system and a major CNS neurotransmitter. The simple ring fluorinated derivatives of (-)- and (+)-norepinephrine [(-)- and (+)6-fluoronorepinephrine] and dopamine (6-fluorodopamine) have been labeled with 18F in high specific activity (2-5 Ci/mumol) and evaluated as tracers for (-)-norepinephrine. Comparative PET studies of (-) and (+)-6-[18F]fluoronorepinephrine [(-)-6-[18F]FNE and (+)-6-[18F]FNE] and 6-[18F]fluorodopamine (6-[18F]FDA) in the same baboon showed strikingly different kinetics in the heart. Analysis of plasma showed more rapid metabolism of 6-[18F]FDA with only 1%-2% of 18F remaining as parent tracer at 10 min after injection of 6-[18F]FDA, in contrast to 28% and 17% remaining after injection of (-) and (+)-6-[18F]FNE. No changes in vital signs were observed at any time during the study. Pretreatment with desipramine (0.5 mg/kg), a tricyclic antidepressant drug which interacts with a binding site associated with norepinephrine reuptake, markedly decreased cardiac uptake of 6-[18F]FDA and (-)-6-[18F]FNE. However, a greater blocking effect was observed for (-)-6-[18F]FNE. These studies show that (-) and (+)-6-[18F]FNE are similar to (-)- and (+)-norepinephrine in their patterns of metabolism and clearance in the heart and that (-)-6-[18F]FNE is a promising tracer for endogenous (-)-norepinephrine.     

Direct approach for attenuating cocaine''s effects on extracellular dopamine: targeting the dopamine transporter

Small cell carcinoma of the larynx is an uncommon epithelial tumor, which is the most aggressive subtype of neuroendocrine carcinomas. Because of its nonspecific clinical and radiological manifestations, the diagnosis of small cell carcinoma of the larynx is essentially based on the light microscopic examination aided by electron microscopy or immunohistochemical staining. We report a case of supraglottic small cell carcinoma accompanied by large bilateral cervical lymph node metastasis ocurring in a 70-year-old man. On CT scans, no area of low attenuation indicating necrosis was demonstrated within such large metastatic lymph nodes. We suggest that small cell carcinoma of the larynx should be included in the diagnostic considerations when a laryngeal mass is accompanied by large cervical lymph nodes without necrosis shown by CT.     

Potential cost savings for Medi-Cal, AFDC, food stamps, and WIC programs associated with increasing breast-feeding among low-income Hmong women in California

OBJECTIVE: To determine the potential cost savings for four social service programs if breast-feeding rates increased among Hmong women in California. DESIGN: Cost-savings analysis. SUBJECTS/SETTING: Hmong women in California. In this population, breast-feeding is currently uncommon, and use of contraceptives is minimal. MAIN OUTCOME MEASURES: Savings were based on estimates of the resulting decrease in infant morbidity, maternal fertility, and formula purchases (Special Supplemental Nutrition Program for Women, Infants, and Children) if women breast-fed each child for at least 6 months. Costs were projected over a 7.5-year period and future values were discounted with annual interest rates of 2% or 4%. RESULTS: Substantial savings estimates were associated with breast-feeding for all four programs. The total projected savings over the 7.5-year period ranges from $3,442 to $4,944 (4% discount) to $4,475 to $6,0960 (0% discount) per family enrolled in all four programs. This translates into an estimated yearly savings of between $459 and $659 (4% discount) and $597 and $808 (0% discount) per family. APPLICATIONS: Although health care providers generally accept that breast-feeding is the preferred method for feeding infants, many still view the choice as a neutral one; that is, they consider low breast-feeding rates in the United States a cultural choice with no cost to society. This analysis provides evidence that breast-feeding is economically advantageous for individuals and society.     

ENZYMATIC HYDROLYSIS OF CELLULOSE: DETERMINATION OF KINETIC PARAMETERS

The effects of cellulose substrate concentration, cellulase enzyme concentration, and product concentration on the kinetic parameters involved in the enzymatic hydrolysis of cellulose have been studied. The Michaelis constant showed a decreasing trend with a decreasing crystallinity of cellulose substrate while the maximum reaction rate showed an increasing trend. These kinetic parameters were found to be significantly larger when the enzyme concentration was increased. The adsorption kinetic parameters showed an increasing trend as the crystallinity is decreased. It was found that the optimal enzyme loading should be determined by the source, concentration, and crystallinity of cellulose substrate and the initial specific rate of cellulose hydrolysis which is, in large part, influenced by the degree of crystallinity of cellulose substrate. The inhibition constant for cellulase-by cellobiose and that for cellobiase were also determined. These kinetic parameters determined experimentally can be applied to kinetic modeling and simulation of cellulose hydrolysis.     

A generalized Vlasov theory for composite beams

A generalized Vlasov theory for composite beams with arbitrary geometric and material sectional properties is developed based on the variational asymptotic beam sectional analysis. Instead of invoking ad hoc kinematic assumptions, the variational-asymptotic method is used to rigorously split the geometrically-nonlinear, three-dimensional elasticity problem into a linear, two-dimensional, cross-sectional analysis and a nonlinear, one-dimensional, beam analysis. The developed theory is implemented into VABS, a general-purpose, finite-element based beam cross-sectional analysis code. Several problems are studied to compare the present theory with published results and a commercial three-dimensional finite element code. The present work focuses on the issues concerning the use of the Vlasov correction in the context of the accuracy of the resulting beam theory. The systematic comparison with three-dimensional finite element analysis results helps to quantitatively demonstrate both the advantages and limitations of the Vlasov theory.     

Generalized Dynamic Models of Gene Expression and Gene Classification

Powerful new experimental methods have been used to monitor changes in gene expression levels as a result of a variety of metabolic, xenobiotic or pathogenic challenges. Here we present a general approach to both statistical analysis and dynamic modeling of gene expression profiles that uses linear response theory.The formalism leads naturally to Markov models of the network reflected in the data, and provides a direct method of classifying genes according to their place in the resulting network. Non-linear and higher order Markov behavior of the network can also be included by a self-consistent method. In a sample data set from yeast, we calculate the Markov matrix and the gene classes based on the linear Markov network.     

The Fundamental Neutron Physics Facilities at NIST

The program in fundamental neutron physics at the National Institute of Standards and Technology (NIST) began nearly two decades ago. The Neutron Interactions and Dosimetry Group currently maintains four neutron beam lines dedicated to studies of fundamental neutron interactions. The neutrons are provided by the NIST Center for Neutron Research, a national user facility for studies that include condensed matter physics, materials science, nuclear chemistry, and biological science. The beam lines for fundamental physics experiments include a high-intensity polychromatic beam, a 0.496 nm monochromatic beam, a 0.89 nm monochromatic beam, and a neutron interferometer and optics facility. This paper discusses some of the parameters of the beam lines along with brief presentations of some of the experiments performed at the facilities.     

Precision Measurement of Fundamental Constants Using GAMS4

We discuss the connection of high-energy gamma-ray measurements with precision atomic mass determinations. These rather different technologies, properly combined, are shown to lead to new values for the neutron mass and the molar Planck constant. We then proceed to describe the gamma-ray measurement process using the GAMS4 facility at the Institut Laue-Langevin and its application to a recent measurement of the 2.2 MeV deuteron binding energy and the neutron mass. Our paper concludes by describing the first crystal diffraction measurement of the 8.6 MeV ³⁶Cl binding energy.