Search PubMed⌕ Search

Biomedical subjects

A Montaser

Publications and source records attributed to A Montaser.

14 recordsLinked to original sources
PubMed2002

Protein-protein interactions in concentrated electrolyte solutions.

Protein-protein interactions were measured for ovalbumin and for lysozyme in aqueous salt solutions. Protein-protein interactions are correlated with a proposed potential of mean force equal to the free energy to desolvate the protein surface that is made inaccessible to the solvent due to the protein-protein interaction. This energy is calculated from the surface free energy of the protein that is determined from protein-salt preferential-interaction parameter measurements. In classical salting-out behavior, the protein-salt preferential interaction is unfavorable. Because addition of salt raises the surface free energy of the protein according to the surface-tension increment of the salt, protein-protein attraction increases, leading to a reduction in solubility. When the surface chemistry of proteins is altered by binding of a specific ion, salting-in is observed when the interactions between (kosmotrope) ion-protein complexes are more repulsive than those between the uncomplexed proteins. However, salting-out is observed when interactions between (chaotrope) ion-protein complexes are more attractive than those of the uncomplexed proteins.

Computer Simulation↗
PubMed2000

Optical patternation: a technique for three-dimensional aerosol diagnostics

A novel technique based on optical patternation is described for three-dimensional diagnostic studies of aerosols used in analytical spectroscopies. The aerosol is illuminated with a thin laser light sheet to capture images of the fluorescence and Lorenz-Mie light-scattering signals from the aerosol field with a charge-coupled detector. These measurements allow for the rapid and nonintrusive elucidation of two-dimensional spray structures, planar mass distributions, and spatial droplet size distributions. The ratio of the fluorescence image to the Lorenz-Mie image is then utilized to construct a spatially resolved map of the volume-to-surface area mean of the aerosol (Sauter mean diameter). Three-dimensional maps of spray structure, mass distribution, and droplet size distribution are obtained for the entire aerosol field by image stacking. The technique is applied to the measurement of the droplet size over the aerosol field at distances of 5-30 mm from the nebulizer tip where droplet sizes ranged from 6 to 12 microm for a direct injection high efficiency nebulizer used in inductively coupled plasma spectrometries.

Journal Article↗
PubMed2000

A large bore-direct injection high efficiency nebulizer for inductively coupled plasma spectrometry

A large bore-direct injection high efficiency nebulizer (IB-DIHEN) is introduced that is less prone to capillary blockage and optimally operates at low nebulizer gas pressures compared with the conventional DIHEN used for inductively coupled plasma (ICP) spectrometries. The aerosol quality is examined using a two-dimensional phase Doppler particle analyzer (2D PDPA), and analytical figures of merits are acquired by ICP mass spectrometry. Compared with the DIHEN, the LB-DIHEN produces larger droplets, but the velocity distributions and mean droplet velocities are narrower and lower, respectively, providing longer residence times for the droplets in the plasma. High RF power (1500 W), low nebulizer gas flow rates (0.25-0.35 L/min), and low solution uptake rates (80-110 microL/min) are required to operate the LB-DIHEN at optimum conditions for ICPMS. Detection limits and sensitivities measured with the LB-DIHEN are superior to those of a conventional nebulizer-spray chamber combination, but precision is inferior. The performance of the LB-DIHEN is further explored in the determination of trace elements in an herbal extract.

Journal Article↗
PubMed1999

Internalization of carcinogenic lead chromate particles by cultured normal human lung epithelial cells: formation of intracellular lead-inclusion bodies and induction of apoptosis.

Occupational exposure to certain particulate hexavalent chromium [Cr(VI)] compounds, such as lead chromate, has been associated with lung cancer and respiratory tract toxicity. We have previously shown that apoptosis is a major mode of death in cultured rodent cells treated with soluble sodium chromate and particulate lead chromate. Here we report the cellular and molecular effects of lead chromate and sodium chromate in normal human lung small airway epithelial (HSAE) cells, which may be one of the targets for Cr(VI)-induced lung cancer and respiratory tract toxicity. Phagocytosed lead chromate particles and intracellular lead-inclusion bodies (LIB) were observed by transmission electron microscopy and confirmed by X-ray analysis. HSAE cells exposed to lead chromate and sodium chromate underwent dose-dependent apoptosis. The cellular uptake and genomic interactions of both Cr and lead (Pb) were examined by inductively coupled plasma mass spectrometry (ICPMS) coupled with a novel, direct-injection high-efficiency nebulizer (DIHEN). Using this approach, we have quantitated a dose-dependent formation of Cr-DNA adducts and DNA-associated Pb in lead chromate-treated HSAE cells. The formation of LIB in normal human lung cells exposed to lead chromate indicates that ionic Pb is released from the particles and thus might contribute to the cell toxicity caused by lead chromate. Internalization and dissolution of lead chromate particles and the interaction of ionic Cr and Pb with DNA, may be components of the mechanism of lead chromate carcinogenesis. Lead chromate-induced apoptosis may be a mechanism to eliminate cells with chromium- and/or lead-damaged DNA.

Apoptosis↗
PubMed1998

A direct injection high-efficiency nebulizer for inductively coupled plasma mass spectrometry.

A simple, relatively low-cost direct injection high-efficiency nebulizer (DIHEN) is introduced for argon inductively coupled plasma (Ar ICP) spectrometry. The DIHEN may be operated at solution uptake rates of 1-100 microL/min. Analytical performance indexes for the DIHEN and fundamental characteristics of the aerosol produced are obtained using an ICP mass spectrometer (ICPMS) and a two-dimensional phase Doppler particle analyzer (2D PDPA), respectively. Results are compared to those obtained with a conventional crossflow pneumatic nebulizer (PN), equipped with a Scott-type spray chamber. Droplet sizes and velocities produced with the DIHEN are smaller than those reported for the direct injection nebulizer (DIN). The DIHEN offers optimal sensitivity at low injector gas flow rates (approximately 0.25 L/min) and high rf power (approximately 1.5 kW). For the 17 elements tested, detection limits (ppt) and sensitivities achieved with the DIHEN (at 85 microL/min) are similar to, or better than, those obtained on the same instrument using the PN (at 1 mL/min). However, because the primary aerosol is injected directly into the plasma, oxide-to-metal ion ratios (MO+/M+) are high, as in the case of the DIN. The utility of the DIHEN for the analysis of small-volume samples is demonstrated by microscale flow injection analysis (muFIA) of Cr bound to human lung DNA. Detection of Cr at the femtogram level is feasible.

Argon↗
PubMed1998

Sensitive quantitation of chromium-DNA adducts by inductively coupled plasma mass spectrometry with a direct injection high-efficiency nebulizer.

A novel method is described for the sensitive detection of chromium-DNA adducts. Chromium-DNA adducts were determined in 1 microgram of DNA from normal human lung fibroblasts exposed to sodium chromate using microscale flow injection analysis with a direct injection high-efficiency nebulizer and inductively coupled plasma mass spectrometry detection. The frequency of Cr-DNA adducts increased in a dose-dependent sigmoidal manner, indicating saturation and toxicity. The low detection limits (on the order of parts per trillion) allows the detection of as few as two Cr adducts per 10,000 bases, which, coupled with the small DNA sample requirement, makes this technique suitable for measuring metal-DNA adducts as biomarkers of exposure to toxic and carcinogenic metals such as Cr, in cultured cells, animals, and humans.

Chromium↗
PubMed1998

Behçet's syndrome: a report of 41 patients with emphasis on neurological manifestations.

Forty one patients with the clinical diagnosis of Behçet's syndrome from two teaching hospitals in Kuwait were studied. There were 34 male and seven female patients. Age at presentation ranged from 14 to 48 years. Neurological manifestations were present in 24 patients. Eleven patients showed evidence of increased intracranial pressure, and 10 of these had radiologically confirmed dural sinus thrombosis. Five patients presented with a meningoencephalitic or meningomyelitic picture, three with a stroke-like picture, and three with primarily brain stem signs. One patient developed trigeminal neuritis, and five patients exhibited (along with other features) variable degrees of psychological manifestations. All patients with neurological involvement were treated with steroids, and some also had courses of other immunosuppressant drugs and colchicine. The disease took a relatively benign course, except those patients with meningoencephalitic and meningomyelitic presentation, one of whom died from the disease. Those treated early had a better prognosis. The incidence of dural sinus thrombosis in this series of patients is unusually high. In most patients, the course of the disease was more favourable than reported in the literature. This may be attributed to early and aggressive treatment.

Adolescent↗
PubMed1996

A status report on helium inductively coupled plasma mass spectrometry.

The current status of helium inductively coupled plasma - mass spectrometry (He ICPMS) is examined, its potentials and limitations are reviewed, and a summary of fundamental properties of atmospheric pressure He ICP discharges is presented. Also included are results of He ICPMS studies with a new helium plasma torch (18 mm i.d.) operated at four sets of operating conditions. Under the "cold plasma" condition (600 W forward power), no secondary discharge is observed and ion kinetic energies ranging from 2.0 eV to 9.5 eV for 6 elements (mass range: 39-208) are measured. At higher power levels, the secondary discharge still is strong. In general, detection limits for certain elements are improved by 1-3 orders of magnitude compared to previous data acquired in 1993 with a 13-mm He ICP torch. Elements such as K, Fe, Cr, Mn, Ni, and Co that suffer from spectral interferences in Ar ICPMS can be detected at pg/mL-levels with an analogue detector and a prototype ICPMS instrument having no photon stops or obstacles present in the ion trajectory path.

Journal Article↗
PubMed1993

Ceruloplasmin and copper transport during the latter part of gestation in the rat.

We have examined the tissue uptake of 67Cu from ceruloplasmin versus albumin and transcuprein, after its intravenous administration to pregnant rats, in the last 4 days of gestation. 67Cu infused as in vivo-labeled ceruloplasmin remained on ceruloplasmin in the maternal circulation over the 4- to 6-hr time period examined, as determined by gel chromatography and immunoreactivity. That infused as in vitro-labeled serum was initially on transcuprein and albumin but soon also with new ceruloplasmin. On the basis of percent dose as well as total actual Cu transferred (taking into account the sizes of the two plasma Cu pools), ceruloplasmin was the preferred source of Cu for most tissues. Total uptake of Cu from ceruloplasmin was seven times greater than that from albumin and transcuprein for the placenta, whole fetus, and fetal liver. It was 2- to 6-fold greater for other tissues (except liver and kidney). When synthesis of maternal 67Cu-ceruloplasmin (from 67Cu administered on albumin and transcuprein) was inhibited with cycloheximide, uptake by nonhepatic tissues was reduced markedly. In the fetal circulation, entering 67Cu was initially associated with transcuprein and alpha-fetoprotein (or albumin), but then also appeared with ceruloplasmin. Specific receptors for ceruloplasmin were detected on membranes from the placenta as well as fetal liver; mRNA for ceruloplasmin was detected on the endoplasmic reticulum-bound polyribosomes of placenta/yolk sac, and of fetal and maternal liver. We conclude that Cu destined for the fetus is delivered mainly or exclusively by ceruloplasmin. It may enter via placental receptors, arriving in fetal plasma in ionic form, for later incorporation into fetal ceruloplasmin. The importance of ceruloplasmin as a source of plasma Cu for nonhepatic organs is also confirmed.

Animals↗
PubMed1992

Comparison of copper binding components in dog serum with those in other species.

The copper content of dog serum and its distribution to copper binding proteins was compared with that of rat and mouse. Total serum Cu concentrations of dogs and mice were one third those of the rat. Plasma ceruloplasmin, determined by azide-inhibitable oxidase activity with two substrates, was 8-fold less in the dog and 9- to 20-fold less in the mouse than in the rat, and, in both dogs and mice, there was 70-75% less ceruloplasmin Cu, determined by atomic absorption after gel filtration. In the dog, the largest proportion of total and exchangeable serum Cu was with the transcuprein fraction. Only one third as much Cu was with albumin in the dog (and mouse) versus the rat, and this was released much more readily through dialysis. In dogs and mice, the exchangeable (nonceruloplasmin) serum copper pool was half the size of that in rats and humans. Especially in the mouse (but also in rats and dogs), a small proportion of the exchangeable pool appeared bound to ferroxidase II. We conclude that the dog may rely more on transcuprein and low molecular weight complexes and less on albumin and ceruloplasmin for transport of copper to cells.

Adult↗
PubMed1989

Thimble glass frit nebulizer for atomic spectrometry.

A thimble-shaped glass frit nebulizer has been developed for atomic spectrometry. The thimble glass frit was pressurized internally by gases such as helium (He) or argon (Ar) while the test solution was applied externally to the frit. The pressurized gas exited through the pores of the glass frit and shattered the thin liquid film flowing on the surface of the thimble-shaped device to form small droplets. A small spray chamber surrounded the nebulizer to remove the large droplets. Small droplets were then introduced into inductively coupled plasmas (ICP) sustained in either Ar or He. To reduce the memory effect noted in the frit-type nebulizers, a clean-out system was also devised. Detection limits, signal-to-background ratios (S/B), precision, memory effects, noise power spectra (NPS), and particle size distributions measured with the new nebulizer were compared to those of disk and cylindrical glass frit nebulizers and the commonly used pneumatic nebulizer for Ar ICP atomic emission spectrometry (AES). Analytical performance was also measured for He ICP by using frit-type nebulizers and an ultrasonic nebulizer.

Nebulizers and Vaporizers↗