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Biomedical subjects

S A Ibrahim

Publications and source records attributed to S A Ibrahim.

At least 73 records · Page 4Linked to original sources
PubMed1990

Ground distribution patterns of selected radioactive, chemical, and physical contaminants from dispersion of U mill tailings.

Ground concentrations of 226Ra and total alpha activity as a function of soil depth and distance from an acidic U mill tailings pile were measured, as well as soil pH, sulfate, chloride, and conductivity. Contamination decreased with increasing soil depth and distance from the source. Most of the measured parameters were indistinguishable from background after a distance of 3.3 km from the tailings impoundment. The highest concentrations of all contaminants were contained in the particles less than 0.045 mm in diameter at the soil surface (0-0.6 cm). This fraction represents only 4% to 10% of the total soil mass. Surface soil particles greater than 2.0 mm contained higher concentrations of all contaminants than the intermediate-size (0.045-2.0 mm) fraction. Aggregate formation of the greater than 2.0-mm fraction from small particles or preferential erosion and transport of the tailings sand fractions were proposed as possible explanations. The significant correlations between various measurements were soil 226Ra vs. total alpha activity, sulfate concentration, and conductivity. The latter two parameters are indicative of sulfuric acid leached tailings. The sulfate concentration appeared to be a sensitive and easily measured indicator of tailings contamination and migration into the soil profile. Furthermore, sulfate may be used to delineate acidic U tailings from other sources of contamination (U ore dust, yellowcake, naturally elevated U and Ra) in the environment. Actual site measurements for surface 226Ra concentration were approximately twice the MILDOS computer code prediction.

Chlorides↗
PubMed1990

Survey of asthma deaths in the Northern region, 1970-85.

Thirty five asthma deaths in children aged 1 to 16 years were investigated in detail. Twenty four of these children had previously been under hospital consultant care and there were seven inpatient deaths. Twenty nine cases (83%) had a history of severe asthma, 17 of whom had previously experienced a life threatening attack. The fatal outcome, however, could not have been predicted in six children (17%) with preceding mild asthma. Potentially preventable factors in management were found in 28 cases (80%). While 18 (51%) had been chronically undertreated, the major factor in 20 deaths (57%) was suboptimal management of the final attack owing to delay in seeking medical attention, inadequate medical response, or both. Only two children had received systemic corticosteroid in appropriate amounts during the final illness. If mortality is to be reduced, families of asthmatic children must be educated to recognise severe symptoms and be given an appropriate 'crisis plan'. Hospitals should permit free access and have a clear protocol for the management of children with severe asthmatic attacks.

Adolescent↗
PubMed1988

Comparative uptake of U and Th by native plants at a U production site.

During a 3- to 4-year period, concentrations of 238U, 234U, 230Th, 232Th and 228Th were determined in soils and native vegetation at various sites around a typical U mining and milling operation in Wyoming. Plant/soil concentration ratios (CR) for U and Th isotopes were estimated for (1) exposed, weathered tailings, (2) the edge of a tailings impoundment, (3) an area downwind from exposed tailings, (4) a reclamation area and (5) several background, native range locations. The 238U/234U concentration ratio of 0.9 to 1.1 in soil and vegetation indicated near-radioactive equilibrium of both radionuclides at all locations. Mean concentrations of the U and Th isotopes in background soil ranged from 44 to 52 mBq g-1. Concentrations of 238U and 230Th in soil and vegetation were elevated above background at all sites disturbed by mining and milling activities. Uranium concentrations in tailings and invading vegetation were an order of magnitude greater than in the background locations, whereas 230Th concentrations were elevated above background by some two orders of magnitude. No demonstrable differences in radionuclide concentrations between plant groups and collection years were found. The observed CR values for 238U and 230Th of 0.81 and 0.69 for vegetation growing on exposed tailings were elevated above native range by factors of 9.0 and 3.6, respectively, and generally higher than other published values. Exceptionally high CR values for 230Th (1.9-2.9) observed near the tailings impoundment demonstrate that under certain conditions, vegetation can accumulate 230Th to a much greater extent than previously reported. Vegetation concentrations were lower for 232Th relative to 230Th and 228Th at locations where they are present at similar soil concentrations.

Colorado↗
PubMed1988

Plant/soil concentration ratios of 226Ra for contrasting sites around an active U mine-mill.

Concentrations of 226Ra were determined in native vegetation and underlying substrate (soil and tailings) at various sites around a conventional open-pit, acid leach U production operation in Wyoming. Plant/soil concentration ratios (CRs) for 226Ra were estimated for various sites, including weathered tailings; a tailings impoundment shoreline; downwind from exposed tailings; a mine overburden reclamation area; and several background locations. Radium-226 concentrations for vegetation and substrate and CR values from the perturbed sites were elevated above background. The highest vegetation concentration (1.3 Bq g-1) was found in a grass which had invaded exposed, weathered tailings. Levels of 226Ra in soil and vegetation and CR values decreased with distance from the tailings impoundment edge. CR values varied significantly among sites, but few differences were found between plant species groups. The observed CR values ranged from 0.07 at the background and reclamation areas to 0.4 downwind from the tailings area. Average CR values for plants growing on exposed tailings and within one meter from the impoundment edge were 0.15 and 0.3, respectively. CR values of 226Ra for plants on tailings substrates were comparatively low in contrast to other radionuclides in the U chain. We speculate that in the case of sulfuric acid leached tailings-derived material, 226Ra is sequestered as sulfate, which is highly insoluble relative to the sulfates of the other elements (e.g., U and Th) resulting in reduced availability for plant uptake.

Metallurgy↗
PubMed1986

Some transition metal chelates of 8-hydroxyquinoline-5-sulfonamides as possible drugs.

Fe(II), Fe(III), Co(II), and Ni(II) chelates with three quinolinol sulfonamides have been prepared and characterized. Characterization of the solids so obtained was accomplished by elemental analysis, electronic and ir spectra, and conductivity measurements. It was found that the sulfonamide ligands act as monobasic bidentate ON donors. The bonding sites are ascertained, and the complexes were all six-coordinate assuming a distorted octahedral geometry. It was identified that the metal chelates possess enhanced antibacterial and antifungal activities relative to the free ligands.

Anti-Bacterial Agents↗
PubMed1984

Kinetics and mechanism of carbonic anhydrase isoenzymes.

A mechanism model has been presented that can describe most known kinetic properties of carbonic anhydrase isoenzymes I, II, and III. The essential features of this model include: Nucleophilic attack of metal-bound OH- on CO2 to form metal-bound HCO-3. Formation of metal-bound OH- from metal-bound H2O. In isoenzyme II, and probably also in isoenzyme I, this reaction step involves an intramolecular transfer of H+ between the metal site and a titratable histidine residue via a number of hydrogen-bonded H2O molecules. In isoenzyme II, this step limits the maximal rate of catalysis. Also in isoenzyme III, the H2O-splitting step may be rate limiting, but since this isoenzyme has no titratable active-site histidine, H+ transfer may take place directly with components of the solvent. In isoenzymes I and II, rapid H+ transfer between active site and solution proceeds in a reaction between the titratable histidine residue and buffer molecules. The model can also rationalize a variety of observed inhibition patterns.

Carbonic Anhydrases↗
PubMed1983

Thorium concentration in human tissues from two U.S. populations.

The concentrations of natural alpha-emitting isotopes of thorium (228Th, 230Th and 232Th) have been determined in 22 sets of human tissue samples obtained at autopsy from Grand Junction, CO and in 10 sets from Washington, DC. Tissues included lung, pulmonary lymph nodes, liver, kidney, bone, a few gonads, spleen and thyroid. Personal data on each individual's age, sex, smoking history and occupation were obtained whenever possible. The concentrations of 228Th, 230Th and 232Th were highest in lymph nodes for both populations with 2.6 and 5.1 pCi/kg of 228Th, 4.60 and 11.10 pCi/kg of 230Th, and 2.8 and 7.8 pCi/kg of 232Th in Washington, DC and Grand Junction, CO, respectively. The order of concentrations of all three isotopes in all other organs for both populations was as follows: (formula; see text) The data suggest that the non-mining residents who lived in the vicinity of uranium mine tailings do not have elevated 230Th concentrations in their lungs, when compared to the residents of Washington, DC who are not exposed to such tailings. However, 230Th concentration in bone of Grand Junction subjects was just significantly higher (at p less than 0.1) than that for Washington, DC subjects after suitable age adjustments. The data also suggest that 230Th is more available for accumulation in skeleton than would be supposed from its relative geochemical abundance.

Adolescent↗
PubMed1983

Plutonium concentration in human tissues: comparison to thorium.

The concentration of 238Pu, and 239,240Pu, and of 228Th, 230Th, and 232Th were measured in 10 sets of human tissues from Washington, DC, and 12 sets from Grand Junction, CO. The tissues were collected at autopsy by qualified pathologists from normal healthy persons most of whom died suddenly. The subjects had acquired plutonium from fallout of global nuclear testing and burnup of a space nuclear generator utilizing 238Pu. The median concentration of 239,240Pu was 0.08 pCi/kg in lung, 0.46 pCi/kg in tracheobronchial lymph nodes, 0.60 pCi/kg in liver, 0.02 pCi/kg in kidney and 0.17 pCi/kg in bone in Washington, DC subjects. Similarly, the concentration of 239,240Pu in Grand Junction subjects was found to be 0.17 pCi/kg in lung, 0.68 pCi/kg in lymph nodes, 0.55 pCi/kg in liver, 0.03 pCi/kg in kidney, 0.22 pCi/kg in bone and 0.08 pCi/kg in spleen. The median concentration in four gonads was 0.02 pCi/kg; the concentration in one thyroid was 0.01 pCi/kg. 238Pu was below the limit of detection in most organs except the liver where it ranged from 0.02 to 0.17 pCi/kg with a median concentration of 0.06 pCi/kg. The organ distribution pattern shows that most of the plutonium was accumulated in bone and liver with 54-60% in bone and 34-43% in liver. Only 3-6% was found in lung including lymph nodes; kidney, spleen, thyroid and gonads together contained around 1%. The analytical results show three major differences between plutonium and thorium concentrations and organ distributions: (1) for plutonium the liver is a major locus for storage (approximately 40% of that found in the total body), whereas little thorium is accumulated in the liver (around 4%); (2) the relative amounts of 230Th and 232Th are much higher in lung and lymph nodes (10-28%) than currently for plutonium (3-6%); (3) the ratio of throium concentrations in lymph nodes to lung is significantly higher than the ratio of plutonium concentration in lymph nodes to lung showing thereby that fallout plutonium is more soluble than natural thorium.

Body Burden↗
PubMed1982

Effect of chelating agents on the stability of injectable isoniazid solutions.

The chelating agents NTA, EDTA, HEDTA and DTPA afford a stabilizing action towards isoniazid solutions. The stabilizing effect of the chelating agents is highly dependent on their concentration. The stability of isoniazid solutions increases markedly with increasing NTA or EDTA concentration up to 1 mmol/l. Beyond this concentration, the stabilizing effect of NTA is more or less independent of its concentration and the dependency of the degradation rate of isoniazid on the concentration of EDTA becomes less pronounced. There is an optimum concentration for HEDTA and DTPA at which their stabilizing effect is maximum; below or above this concentration, the stability of isoniazid decreases. The stabilizing efficiency of the investigated chelating agents decreases in the order DTPA greater than HEDTA greater than EDTA greater than NTA, which runs parallel with the stability constants of their metal chelates.

Chelating Agents↗
PubMed1980

Availability of oxyphenbutazone from different suppository formulations.

The in vitro release of oxyphenbutazone as well as its rectal absorption in rabbits from different suppository formulations were investigated. It was proved that polyethylene glycol base gave higher medicament release than adeps solidus base. Incorporation of nonionic surfactants in Witepsol H 15 increased or decreased oxyphenbutazone release while incorporation of hydrophilic aerosil caused a reduction in the released amount of the medicament. A mixture of Witepsol H 15 or H 12 and Brij 58 (85:5) gave the highest in vitro release and the highest rectal absorption of the medicament. A correlation was found to exist between the in vitro release of oxyphenbutazone and its rectal absorption in rabbits.

Animals↗