Naphthol- and resorcinol-based azo dyes as metal ion complexants in aqueous biphasic systems.

Aqueous biphasic systems (ABS) are comprised of both a polymer-rich phase (e.g., polyethylene glycol, PEG) and a salt-rich phase [e.g., (NH4)2SO4] such that both phases are 80% water on a molar basis. ABS have demonstrated applications as environmentally-friendly methods to separate relatively hydrophobic anionic species, such as pertechnetate and mercury halide anionic complexes, from high ionic strength solutions although partitioning of hydrated metal ions, such as Fe3+ and actinides, to the PEG-rich phase is negligible without the addition of a metal ion complexant to the system. Four naphthol- or resorcinol-based dyes; 1-(2-pyridylazo)-2-naphthol (PAN), 1-(thiazolylazo)-2-naphthol (TAN), 4-(2-pyridylazo)-resorcinol (PAR) and 4-(2-thiazolylazo)-resorcinol (TAR), each incorporating a naphthol or resorcinol with an ortho azo functional group, have been studied as metal ion extractants in ABS as a function of pH. In the PEG-2000/ (NH4)2SO4 ABS, the distribution ratios of Fe3+, Co2+ and Ni2- were enhanced by several orders of magnitude at high pH in contrast to the behavior of Cs+, Cd2+ and Eu3+ whose partitioning behavior was largely unaffected by the presence of these extractants at any pH. The three extracted metal ions, Fe3+, Co2+ and Ni2+, could be stripped by contact with a fresh salt phase at low pH.

Increased levels of transcription factors Elk-1, cyclic adenosine monophosphate response element-binding protein, and activating transcription factor 2 in the cerebellar vermis of schizophrenic patients.

BACKGROUND: We investigated the levels of transcription factors associated with activation of the mitogen-activated protein (MAP) kinase pathway in schizophrenics using postmortem brain samples. These studies were done to determine whether our previous findings of abnormal levels of the MAP kinases in the cerebellar vermis were linked to additional downstream targets of this signal transduction pathway. METHOD: We measured the protein levels of 3 transcription factors in nuclear fractions of postmortem samples from cerebellar vermis of 10 patients with schizophrenia and 13 control subjects: Elk-1, cyclic adenosine monophosphate (cAMP) response element binding protein (CREB), and activating transcription factor 2 (ATF-2). Studies in rats examined the postmortem stability and effect of haloperidol and risperidone on levels of Elk-1, cAMP, and ATF-2 proteins. RESULTS: We found a significant increase in the protein levels of Elk-1 (mean+SD, 4489+/-659 vs 2915+/-583 arbitrary densitometric units [P<.001]), CREB (mean +/- SD, 2149 1061 vs 904+/-711 arbitrary densitometric units [P=.003]) and ATF-2 (mean+/-SD, 1421 854 vs 512+/-394 arbitrary densitometric units [P=.003]) in the cerebellar vermis of schizophrenic subjects. Complementary studies in rats indicate that these findings can not be attributed to subacute treatment with antipsychotic medications. CONCLUSION: Taken together with the alterations of MAP kinases previously reported, and the findings of elevations of downstream transcription targets, we suggest that the MAP kinase signal transduction pathway contributes to the cerebellar abnormalities in schizophrenia.

Partitioning of small organic molecules in aqueous biphasic systems.

Aqueous biphasic systems (ABS) are suitable for the separation of small organic molecules in industrial and environmental applications and thus, it is important to correlate partitioning behavior of model organic solutes with their structure in order to develop predictive models. The partitioning behavior of five, uncharged, substituted benzenes (benzene, toluene. chlorobenzene, 1,4-dichlorobenzene and 1,2,4-trichlorobenzene) were studied in ABS prepared from stock solutions of 40% (w/w) PEG-2000 and increasing concentrations of four water-structuring salts (K3PO4, K2CO3, (NH4)2SO4 and NaOH). For a given solute and a defined concentration of salt, the partition coefficients increase as the deltaGhyd value of the salt anion becomes more negative (e.g., Dbenzene increases in the order OH-

Partitioning of mercury in aqueous biphasic systems and on ABEC resins.

Poly(ethylene glycol)-based aqueous biphasic systems (PEG-ABS) can be utilized to separate and recover metal ions in environmental and hydrometallurgical applications. A concurrent study was conducted comparing the partitioning of mercury between aqueous layers in an ABS [Me-PEG-5000/(NH4)2SO4] and partitioning of mercury from aqueous solutions to aqueous biphasic extraction chromatographic (ABEC-5000) resins. In ammonium sulfate solutions, mercury partitions to the salt-rich phase in ABS, but by using halide ion extractants, mercury will partition to the PEG-rich phase after formation of a chloro, bromo or iodo complex. The efficacy of the extractant increases in the order Cl-

Aging-associated changes in human brain.

A wide variety of anatomic and histological alterations are common in brains of aged individuals. However, identification of intrinsic aging changes--as distinct from changes resulting from cumulative environmental insult--is problematic. Some degree of neuronal and volume loss would appear to be inevitable, but recent studies have suggested that the magnitudes of such changes are much less than previously thought, and studies of dendritic complexity in cognitively intact individuals suggest continuing neuronal plasticity into the eighth decade. A number of vascular changes become more frequent with age, many attributable to systemic conditions such as hypertension and atherosclerosis. Age-associated vascular changes not clearly linked to such conditions include hyaline arteriosclerotic changes with formation of arterial tortuosities in small intracranial vessels and the radiographic changes in deep cerebral white matter known as "leukoaraiosis." Aging is accompanied by increases in glial cell activation, in oxidative damage to proteins and lipids, in irreversible protein glycation, and in damage to DNA, and such changes may underlie in part the age-associated increasing incidence of "degenerative" conditions such as Alzheimer disease and Parkinson disease. A small number of histological changes appear to be universal in aged human brains. These include increasing numbers of corpora amylacea within astrocytic processes near blood-brain or cerebrospinal fluid-brain interfaces, accumulation of the "aging" pigment lipofuscin in all brain regions, and appearance of Alzheimer-type neurofibrillary tangles (but not necessarily amyloid plaques) in mesial temporal structures.

Metal ion separations in polyethylene glycol-based aqueous biphasic systems: correlation of partitioning behavior with available thermodynamic hydration data.

Solvent extraction utilizing an oil-water mixture (e.g., chloroform-water) and a suitable complexant, is a proven technology for the selective removal and recovery of metal ions from aqueous solutions. Aqueous biphasic systems (ABS), formed by mixing certain inorganic salts and water-soluble polymers, or by mixing two dissimilar water-soluble polymers, have been studied for more than 40 years for the gentle, non-denaturing separation of fragile biomolecules, yet ABS have been virtually ignored as a possible extraction technology for metal ions. In this report we review our metal ion partitioning work and discuss the three major types of partitioning: (1) those rare instances that the metal ion species present in a given solution partitions to the PEG-rich phase without an extractant; (2) the use of halide salts which produce a metal anion complex that partitions to the PEG-rich phase; and (3) the use of a water-soluble extractant which distributes to the PEG-rich phase. In addition, we correlate the partitioning behavior we observed with available thermodynamic data for metal ions and their complexes.

Axial evolution of the negative glow in a hollow cathode discharge.

The purpose of these studies was to examine the axial evolution of the negative glow in a hollow cathode discharge. The time-average negative glow profiles along the central axis of a hollow cathode were recorded for 81 pulse widths over the range of 5-25 microseconds in increments of 0.25 microseconds at a constant interpulse delay of 206.4 microseconds. Subsequent numerical processing yielded the instantaneous negative glow profile. The negative glow was viewed through a mesh-covered slot along the length of the hollow cathode. The negative flow profiles were imaged using a vidicon video camera. A PC-based frame grabber digitized the video images and stored them for subsequent processing.

Effect of aging the hollow cathode by sputtering on the analytical precision of the hollow cathode discharge emission source.

Sputtering changes the analytical performance of the hollow cathode as an emission source. Proper conditioning (aging) of the hollow with sputtering greatly improves precision. Conditioning decreases the blank emission signal and changes the shape of the hollow. Micrographs which show the evolution of the bottom of the hollow into a stable bulb shape are presented. The blank emission signal decreases with aging of the hollow and approaches a constant value when the hollow is properly conditioned. A short-term stability (n = 5) of approximately 1.8% RSD has been observed frequently. An average long-term stability over several days (n = 45) of 4.5% for Li and 3.5% for Na in the emission signal from microsamples (less than 50 nL) deposited in the hollow cathode discharge source is reported here. Instrumentation, operation, and sample preparation procedures are described.

Comparison of continuous and discrete frequency-versus-radius frequency-modulated reticles.

We present a general expression for the transmission function of the discrete frequency-versus-radius reticle and compare such a reticle with the more common continuous reticle. A discrete form of the frequency-versus-radius reticle has an integer number of chopping cycles on a single radius. The discreteform limits the resolution of the reticle in the radial direction, but this limit is not severe for small-target images. However, since no phase reversal occurs, electronic processing is simplified.

Increased analytical precision in the hollow cathode discharge emission source by improved discharge current control.

A significant improvement in the precision of the hollow cathode as an emission source is reported. Precision of 1% or less has been observed several times over periods of several hours. An average long-term stability of 4.3% for Ll and 6.0% for Na in the emission signal from microsamples (less than 50 nL) deposited in the hollow cathode discharge source is reported. The improved precision is attributed primarily to the introduction of electronics that hold the discharge current more nearly constant and to the shielding of all wiring to the source from the power supply. A current-controlled switch that is capable of driving a hollow cathode discharge in either dc or pulsed mode is described. This switch is capable of generating current pulses as short as 2 microseconds through a resistive load and greatly improves the discharge stability and repeatability at turn-on in both the dc and pulsed modes. The characteristics of pulses produced by this switch are presented; however, analytical performance is reported only for the dc mode. Temporal current plots are presented for the new instrumentation and compared to plots taken with commonly used current-controlled power supplies. Instrumentation, operation, and sample preparation procedures are described. Typical temporal profiles of the emission signal from microsamples deposited in AI and stainless steel hollow cathodes are given.