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Biomedical subjects

M L Jackson

Publications and source records attributed to M L Jackson.

47 records · Page 3Linked to original sources
PubMed1985

The effect of oral phenylbutazone on whole blood platelet aggregation in the dog.

Platelet aggregation to collagen, arachidonic acid and adenosine diphosphate was evaluated in six dogs using a whole blood electronic aggregometer. The six dogs were then given phenylbutazone orally according to four different dosage levels and durations of treatment. Aggregation responses were measured at established intervals of time following phenylbutazone administration. Data on untreated dogs indicated that arachidonic acid, at a final concentration of 50 micrograms/mL and collagen, at a final concentration of 5 micrograms/mL, were useful agents for studying whole blood platelet aggregation in the dog, but adenosine diphosphate, at a final concentration of 30 microM was not. The high single dose (900 mg) of phenylbutazone significantly inhibited platelet aggregation to arachidonic acid at 1.5,4,7 and 12 hours following administration. The results indicated that the whole blood electronic aggregometer was of limited value in detecting subtle changes in platelet aggregation. It was concluded, however, that the instrument is potentially useful as a rapid screening aid for detecting canine patients at high risk of platelet-related bleeding problems.

Adenosine Diphosphate↗
PubMed1984

Isolation and identification of the phosphorylated species of rhodopsin.

Rhodopsin is phosphorylated in a light-dependent manner by a kinase intrinsic to the rod outer segment. We have used chromatofocusing to separate six phosphorylated species of rhodopsin and have recovered in the pH gradient fractions 60-80% of the initial phosphorylated sample loaded on the column. The isolated species of rhodopsin coincide with the species that are observed in isoelectric focusing gels in the pH range 6.1-4.7. Unphosphorylated rhodopsin focuses at a pI of 6.0. Two species having two phosphates per rhodopsin with isoelectric points of 5.45 and 5.40 have been isolated. The phosphate to rhodopsin ratios for the remaining species are 3.8, 5.0, 6.1, and 8.2 with isoelectric points of 5.16, 4.99, 4.85, and 4.73, respectively. The chromatofocusing profile suggests that there may be multiple forms of rhodopsin with the same number of phosphates among some of the other phosphorylated forms of rhodopsin.

Animals↗
PubMed1984

Rings of cross-striated fibrils within the cat cone pedicle: a computer-assisted serial EM analysis.

Using serial electron micrographs and a computer reconstruction system the authors have examined the three-dimensional cytoarchitecture of the cat cone pedicle. These reconstructions reveal that within each pedicle is a closed 4-6 micron diameter ring of cross-striated fibrils similar to the nonring structures described in photoreceptor inner and outer segments by others in guinea pig, rat, chick, monkey, and humans. Our cone pedicle rings encompass the invaginating synaptic contacts of the cone bipolars and horizontal cells and have periodic 70 nm striations surrounding bundles of fibrils about 100 nm in diameter. The authors suggest that these striated rings may be active contractile elements and could be responsible for shape changes in cone pedicles during dark adaptation.

Animals↗
PubMed1983

Aluminum of acid soils in the food chain and senility.

Aluminum is liberated from aluminosilicates of soil clays and protracted Al intake by humans in food and medications has been shown to be a potential hazard to human health. Encephalopathology, senility, and lower statistical longevity were found to be geographically and geochemically linked to acid soil conditions. We examined the interrelation of soil environmental supply of Al3+(6H2O) to the food-plant-animal-human chain (e.g., in tea leaves, approximately 1000 mg L-1) and to identified health hazards. Because F forms a strong ligand with Al, we also analyzed the extent that F accumulation is associated with Al accumulation in plants such as tea. Food and medicinal intake of Al needs to be considered in relation to kidney weakness and Al accumulation in humans. Acid soil and plant management could be modified to reduce the hazard of Al in senile dementia (2 to 4 percent of persons age greater than 65 years) and in diseases of the central nervous system endemic in certain acid soil areas.

Aluminum↗
PubMed1982

Rhodopsin-phospholipid reconstitution by dialysis removal of octyl glucoside.

Recombinant membranes were prepared from phospholipid-free rhodopsin and egg phosphatidylcholine (PC) under a wide variety of conditions employing an octyl beta-D-glucoside (OG) dialysis procedure. Two bands were consistently observed after sucrose density centrifugation of these recombinants. The major band, which was protein rich, had a molar phospholipid:protein ratio that was in the range of 30:1 to 50:1, even when the molar phospholipid:protein ratio of the solubilized solution prior to OG removal was as high as 300:1. Similar results were obtained when dioleoyl-PC, 1-palmitoyl-2-oleoyl-PC, disk lipids, or diphytanoyl-PC was used instead of egg PC. These results can be explained in terms of a lower stability of the OG-phospholipid micelles relative to the OG-phospholipid-rhodopsin micelles. Of the phospholipids that were used in the OG dialysis procedure, only saturated dimyristoyl-PC produced a protein-rich recombinant band with a phospholipid:protein ratio close to that of the initial solubilized solution. In contrast to the results obtained by using OG, when solubilized disks supplemented with egg PC were reconstituted from sodium cholate or dodecyltrimethyl-ammonium bromide, the resulting recombinant membranes had initial and final phospholipid:protein ratios which were similar.

Animals↗
PubMed1982

Solubilization of phosphatidylcholine bilayers by octyl glucoside.

The solubilization of large, unilamellar egg phosphatidylcholine vesicles by the nonionic detergent octyl glucoside (OG) was investigated by nuclear magnetic resonance (NMR), fluorescence anisotropy, turbidity, electron microscopy, and centrifugation followed by compositional analysis. The solubilization process is well described by the three-stage model previously proposed for other detergents. In stage I, the OG partitions between the bilayer and aqueous phases with a molar partition coefficient of 59 +/- 6. The presence of OG in the bilayers produces a small "fluidizing" effect, as indicated by changes in the NMR and fluorescence anisotropy parameters. A rearrangement that forms large mixed bilayers occurs in the latter part of stage I. Stage II, the conversion of detergent-saturated bilayers into mixed micelles, begins at a ratio of total OG concentration minus the critical micelle concentration to total phosphatidylcholine concentration of approximately 1.5 and continues until this ratio reaches about 3.0. The correction for the critical micelle concentration of the OG is necessary for comparison of experimental results obtained at different lipid concentrations. The mixed bilayer-mixed micelle interconversion is quantified by the centrifugation experiments and by 31P NMR. The agreement between the two methods is excellent. Advantages of the NMR method are discussed. In stage III, which was not studied in detail here, all of the phosphatidylcholine is present as mixed micelles. Evidence is presented that the various structures present in the dispersions are in equilibrium with one another during these experiments.

Fluorescence Polarization↗
PubMedDate not supplied

Selenium: geochemical distribution and associations with human heart and cancer death rates and longevity in China and the United States.

The geochemistry of available soil Se varies enormously in different localities, and the corresponding amounts moving up through crops to food vary accordingly. In a belt extending from northeastern to south central China, the available soil Se was measured by human blood Se levels. Severe deficiency occurred at 8-26 ng/mL; subadequate amounts occurred in large areas with 32-83 ng/mL; adequate amounts of 200-300 ng/mL occurred in large cities; and toxic amounts of 3000-7800 ng/mL occurred in terrace areas where runoff from the uplands evaporated, and in certain other soils. Some heart deaths (Keshan Disease) occurred in children 1 to 10 yr of age in the most deficient areas, but were prevented by 230-900 micrograms/wk Se supplementation. One mg Se/wk was the adult dosage. In Se deficient areas, the life span of adults was lowered severely (35 to 45 yr), with heart muscle damage common at autopsy. Se and Zn deficiencies are apparently associated with stomach cancer. The geochemistry of Se in the USA is also highly variable, blood Se ranging from 100-350 ng/mL. Se data for individuals are limited; however, ischemic heart death correlated inversely with blood Se in 25 cities of 22 states (r = -.70; p less than .01). Counties of Wisconsin and Florida are highly variable in human heart death and cancer death rates, as are the 50 states, suggesting Se geographic variability.

Animals↗
PubMedDate not supplied

Evaluation of leachates from coal refuse blended with fly ash at different rates.

There is great interest in returning coal combustion products to mining sites for beneficial reuse as liming agents. A column study examined the effects of blending two coal fly ashes with an acid-forming coal refuse (4% pyritic S). Both fly ashes were net alkaline, but had relatively low neutralizing capacities. One ash with moderate alkalinity (CRF) was bulk blended with coal refuse at 0, 20, and 33% (w/w), while another lower alkalinity ash (WVF) was blended at 0, 5, 10, 20, and 33% (w/w). The columns were leached (unsaturated) weekly with 2.5 cm of simulated precipitation for >150 wk. Where high amounts of ash alkalinity (>20% w/w) were mixed with the coal refuse, pyrite oxidation was controlled and leachate pH was >7.0 with low metal levels throughout the study. At lower rates of alkalinity loading, trace metals were sequentially released from the WVF ash as the 5, 10, and 20% treatments acidified due to pyrite oxidation. Lechate metals increased in proportion to the total amounts applied in the ash. In this strongly acidic environment, metals such as Mn, Fe, and Cu were dissolved and leached from the ash matrix in large quantities. If ash is to be beneficially reused in the reclamation of acid-producing coal refuse, the alkalinity and potential acidity of the materials must be balanced through the appropriate addition of lime or other alkaline materials to the blend. Highly potentially acidic refuse material, such as that used here, may not be suitable for ash/refuse codisposal scenarios.

Coal↗