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Biomedical subjects

C Kennedy

Publications and source records attributed to C Kennedy.

At least 325 records · Page 18Linked to original sources
PubMed1977

Mercury pigmentation from industrial exposure. An ultrastructural and analytical electron microscopic study.

A study has been made of facial pigmentation resulting from industrial inorganic mercury exposure. Electron microscopy has shown electron-dense 400--900 nm aggregates of 12 nm particles in dermal macrophages and free in the dermis. Use of the analytical electron microscope has enabled direct confirmation of the presence of mercury in these aggregates. The unexpected finding of coexistent selenium is discussed.

Environmental Exposure↗
PubMed1977

Assessment of a method for measuring serum thyroxine by radioimmunoassay, with use of polyethylene glycol precipitation.

We assessed the efficacy of a new thyroxine radioimmunoassay kit (Abott) in which polyethylene glycol is used to separate bound from free hormone. Mean serum thyroxine was 88 +/- 15 (+/-SD) microgram/liter for 96 normal persons. Results for hypothyroid and hyperthyroid persons were clearly separated from those for normal individuals. Women taking oral contraceptive preparations showed variable increases in their serum thyroxine values. The coefficient of variation ranged from 1 to 3% within assay and from 5.4 to 11% among different assays. Excellent parallelism was demonstrated between thyroxine values estimated by this method and those obtained either by competitive protein binding or by a separate radioimmunoassay for the hormone.

Adolescent↗
PubMed1976

The molybdenum--iron protein of Klebsiella pneumoniae nitrogenase. Evidence for non-identical subunits from peptide 'mapping'.

The molybdenum- and iron-containing protein components of nitrogenase purified from Klebsiella pneumoniae, Azotobacter vinelandii, Azotobacter chroococcum and Rhizobium japonicum bacteroids all gave either one or two protein-staining bands after sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, depending on the commercial brand of sodium dodecyl sulphate used. The single band obtained with K. pneumoniae Mo-Fe protein when some commercial brands of sodium dodecyl sulphate were used in the preparation of the electrode buffer was resolved into two bands by the addition of 0.01% (v/v) dodecanol to the buffer. Protein extracted from the two bands obtained after electrophoresis of K. pneumoniae Mo-Fe protein gave unique and distinct peptide 'maps' after tryptic digestion. Undissociated Mo-Fe protein contained both sets of tryptic peptides. These data are consistent with Mo-Fe protein from K. pneumoniae being composed of non-identical subunits. Amino acid analyses of the subunit proteins revealed some clear differences in amino acid content, but the two subunits showed close compositional relatedness, with a different index [Metzer, H., Shapiro, M.B., Mosiman, J.E. & Vinton, J.G. (1968) Nature (London) 219, 1166-1168] of 4.7.

Amino Acids↗
PubMed1976

Metabolic anatomy of focal motor seizures.

Contralateral focal seizures occurred in rats following the intracortical injection of penicillin into the anterior motor cortex. The anatomic dimensions of the metabolic response in the focus as well as the spread of increased activity through the brain were studied by autoradiography following intravenous injection of carbon 14-labeled 2-deoxyglucose. Injections of 25 to 200 units of penicillin resulted in mild to severe contralateral motor jerks coincident with repetitive single spike discharges on the electroencephalogram. Concurrent autoradiography revealed a 1.3- to 2.5-fold increase in metabolic activity in discrete areas in ipsilateral cortex, basal ganglia, thalamus, and contralateral cerebellum. Intracortical injections of over 300 units resulted in the development of recurrent contralateral tonic-clonic seizures, with 20% becoming bilateral. In brains of these animals there was activation of bilateral medial frontal cortex, bilateral extrapyramidal system, thalamus, cerebellum, and limbic structures.

Amygdala↗
PubMed1976

Metabolic mapping of the primary visual system of the monkey by means of the autoradiographic [14C]deoxyglucose technique.

An autoradiographic technique that employs 2-[14-C]deoxyglucose to measure the local rates of glucose utilization within the brain has been applied to the binocular visual system of the Macaque monkey. This method, which pictorially displays the relative rates of glucose consumption in the component structures of the brain, delineates the regions of altered functional activity because of the close relationship between functional activity and energy metabolism. Bilateral retinal stimulation results in the delineation of different rates of glucose consumption in at least four cytoarchitectural layers of the striate cortex. The most intense metabolic activity appears to be in Layer IV, the locus of the termination of the geniculocortical pathway. Bilateral visual occlusion lowers the rates of glucoes consumption in striate cortex and markedly reduces the metabolic differentiation of the various layers. Unilateral visual deprivation delineates the laminae of the lateral geniculate body and the ocular dominance columns of the striate cortex. It also results in the autoradiographic visualization of regions with normally monocular input in the striate cortex, such as the rostral portions of the mushroom-like configurations in the calcarine cortex, which represent the extreme temporal crescents of the visual fields, and small regions in the most caudal part of the mushroom configurations, which are believed to represent the cortical loci of the blind spotsof the visual fields.

Animals↗
PubMed1975

A method for isolating nonsense suppressors in enterobacteriaceae using an amber mutant of the drug resistance factor R1.

We describe here the isolation of a mutant derivative of the drug resistance factor R1 (Meynell and Datta, 1966) that carries a nonsense mutation in a gene determining resistance to penicillins. We have used this mutant R1 to isolate derivatives of Escherichia coli and Klebsiella pneumoniae that contain nonsense suppressors (Sup- strains) by screening penicillin-resistant revertants of strains containing the mutant R factor for the presence of such suppressors. This obviates the need to have known nonsense mutations in chromosomal genes. Theoretically, suppressor-containing derivatives of any bacterial species that can maintain and express R1 can be constructed.

Escherichia coli↗
PubMed1975

Mapping of functional neural pathways by autoradiographic survey of local metabolic rate with (14C)deoxyglucose.

An enzymatic preparation from human brain converts tryptamine to tryptoline (9H-1,2,3,4-tetrahydropyrido(3,4-b)indole) in the presence of 5-methyltetrahydrofolic acid. Similarly, N-methyltryptamine and 5-hydroxytryptamine yield 1-methyltryptoline and 5-hydroxytryptoline, respectively. Neither in vitro nor in vivo formation of these compounds by human tissues has been described.

Animals↗
PubMed1975

Permeability limitation in estimation of local brain blood flow with [14C]antipyrine.

Influence of capillary permeability on local cerebral blood flow (LCBF) estimated by the autoradiograhpic diffusible-indicator method was analyzed by computer simulation. Its influence increases with increasing flow. With normal perfusion rates in gray matter, capillary permeability coefficient x surface area (PS value) must exceed 0.12 cm3-s(-1)-g(-1) for estimated LCBF to attain 95% of true values in all structures. In white matter, with its lower perfusion rates, the PS value must exceed 0.035 cm3-s(-1)-g(-1) for equivalent accuracy. [14C]antipyrine, widely used in the LCBF technique, has a PS value below these values and leads to undersestimation of LCBF. Experimental studies in cats in which LCBF was measured with either [14C]antipyrine or the freely diffusible, radioactive gas, [131I]trifluoroiodomethane, demonstrated consistently lower estimates of LCBF with [14C]antipyrine than with the gas; the deviations in the various cerebral structures approximated those predicted by the theoretical analyses. These results suggest that the uptake of [14C]antipyrine by cerebral tissues is diffusion limited as well as flow limited, and it therefore is not an ideal tracer for the autoradiographic LCBF technique.

Animals↗