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Biomedical subjects

J Davis

Publications and source records attributed to J Davis.

At least 451 records · Page 25Linked to original sources
PubMed1982

Preparation of 11C-methyl iodide and L-[S-methyl-11C]methionine by an automated continuous flow process.

A continuous flow procedure has been developed for the synthesis of 11C-methyl iodide and L-[S-methyl-11C]methionine from 11CO2. The preparation can be completed in 20 min after the end of bombardment. This procedure results in the production of approximately 44 mCi 11C-methyl methionine with a specific activity of 3.3 Ci/mmol. Radiochemical purity is greater than 96%. The procedure has been automated so that the preparation can be carried out remotely, thus minimizing exposure of personnel to radiation.

Carbon Radioisotopes↗
PubMed1982

Effects of particle size and perfusate composition on the uptake of colloidal gold by the rabbit thoracic aorta perfused in situ.

The influence has been investigated of particle size on the uptake of radioactive gold colloid by the rabbit thoracic aorta perfused in situ. Particles ranging in diameter from 14 nm to 40 nm were suspended in 0.9% NaCl and infused either at a pressure of 15 mm Hg for times of between 2 1/2 and 60 min or at pressure of between 15 and 160 mm Hg for 5 min. Uptake by the whole intima-media increased with perfusion time and hydrostatic pressure but did not depend on particle size. Radioactive assay of serial sections across the aortic wall also showed that particle size did not influence the distribution of tracer. An effect of perfusate composition on uptake was demonstrated in further experiments in which particles either 14 or 40 nm in diameter were suspended in pooled rabbit serum and infused at pressures of between 15 and 140 mm Hg for 5 min. Uptake and transmural distribution were again independent of particle size, but uptake was 4-5-fold less than when the particles were perfused in saline. Under all perfusion conditions radioactivity fell steeply across the intima and then rose gradually across the media and adventitia. Radioactivity in the outer media and adventitia increased with perfusion time but little change could be detected in intimal activity. In transmission electron micrographs, particles in the intima were not seen to penetrate the internal elastic lamella and in the outer media particles remained extracellular and did not enter collagen bundles. Autoradiographs showed that particles in the intima were uniformly distributed around the circumference of the vessel but in the outer media and adventitia particles usually clustered close to the vasa vasorum.

Animals↗
PubMed1982

Pediatric screening of Southeast Asian immigrants.

Statistics from the first three months of operation of the Santa Clara County Indochinese Health Screening Clinic were analyzed for prevalence of anemia, parasitism, and exposure to tuberculosis in Southeast Asian children and young adults, ages 9 months to 24 years. Anemia was extremely common in infants up to 5 years of age (35.7%) and decreased to 4.8% in the 15-24 year-old category. Parasitism was not-age-dependent, with an average of 58.8% per cent of those screened exhibiting infestation. Positivity in tuberculin skin testing showed a pattern opposite to that of anemia, with a prevalence of 13 per cent in infants and children, rising to 34 per cent in young adults. Over 90 per cent of the target population was successfully screened. Health problems of Indochinese immigrants may be age-related and are very efficiently and effectively identified by an area-wide screening program.

Adolescent↗
PubMed1982

Lactoferrin interacts with deoxyribonucleic acid: a preferential reactivity with double-stranded DNA and dissociation of DNA-anti-DNA complexes.

LF was found to bind to deoxyribonucleic acid as assessed by immunofluorescence studies on cell nuclei, affinity chromatography of DNA on immobilized LF, and gel chromatography of an LF-DNA reaction mixture. LF immobilized on Sepharose 4-B was reacted with 125I-labeled DNA in both its double-stranded and single-stranded configurations; dsDNA eluted with a 0.69M NaCl buffer, whereas ssDNA eluted with a 0.25M NaCl buffer. Additional evidence for a preferential reactivity with dsDNA was provided by the enzymatic treatment of preformed dsDNA-LF and ssDNA-LF complexes with S1 endonuclease, and DNAse 1--DNase digestion alone liberated free LF. The interaction of LF with DNA partially inhibited the binding of anti-DNA antibodies from patients with SLE, as assayed in a standard Farr assay. Furthermore, DNA-anti-DNA (labeled with 125I-IgG) complexes could be dispersed in vitro by the addition of LF. It is hypothesized that the release of LF by neutrophils chemotactically attracted to DNA-anti-DNA complexes may act as a feedback loop to modulate the inflammatory response in SLE.

Antigen-Antibody Complex↗
PubMed1982

Salmonellosis in infants: the importance of intrafamilial transmission.

In a retrospective review of Wisconsin Salmonella surveillance data, we found that 73 (39%) of 187 families with infant index patients has at least one family members with prior diarrheal illness, compared with only 20 (13%) of 158 families with 5- to 9-year-old index patients (P less than .0001). Prior diarrheal illness was also more commonly identified in families with an infant index patient 0 to 2 months of age (28 of 52 families) than in families with an index patient 3 to 11 months (45 of 135 families) (P less than .02); this difference was found largely in families of infant index patients with siblings. Intrafamilial transmission of Salmonella may explain a large proportion of cases of infant salmonellosis. Older children and adults with salmonellosis may be the most important exposures for infants 0 to 2 months of age.

Child↗
PubMed1981

Molecular complexes involved in the regulation of adenylate cyclase.

Selective extraction of the adenylate cyclase regulatory protein (N-protein) from pigeon erythrocyte plasma membranes provided evidence for its cytoskeletal association. Cholate, but not Triton X-100 or digitonin, was effective in solubilizing the ADP-ribosylated N-protein. The labeled protein complex or components thereof that were associated with the Triton-insoluble cytoskeleton (shells) could be partly released by 0.1 mM EDTA; 1 M KCl in the presence of Triton X-100 achieved complete solubilization. 5'-Guanylyl imidodiphosphate (p[NH]ppG) and NaF, activators of adenylate cyclase, promoted the release of the regulatory protein from the cytoskeleton but MnCl2, an "uncoupler" of the adenylate cyclase system, had the opposite effect. The solubilized, labeled N-protein was able to bind specifically to rat erythrocyte inside-out vesicles in the presence of divalent cations. A proteolytic product of inside-out vesicles inhibited the binding of the N-protein to fresh vesicles. Three molecular species which contained the Mr 45,000 polypeptide component of the N-protein were identified by gel permeation chromatography and by sucrose density gradient velocity sedimentation. p[NH]ppG appeared to convert the two larger molecular complexes to a smaller molecular entity. Such a molecular dissociation might be relevant to the effects of guanyl nucleotides on the activity of adenylate cyclase and on the affinity of hormone receptors.

Adenylyl Cyclases↗
PubMed1981

Erythrocyte ankyrin: immunoreactive analogues are associated with mitotic structures in cultured cells and with microtubules in brain.

Human erythrocyte ankyrin, the membrane attachment protein for spectrin, has been detected by radioimmunoassay in a variety of cells and tissues. This report identifies polypeptides crossreacting with ankyrin in brain and HeLa cells and demonstrates that one function of these ankyrin analogues involves association with microtubules. Ankyrin immunoreactivity was localized by indirect immunofluorescence in a colchicine- and detergent-sensitive cytoplasmic meshwork in interphase cells. There also was specific nuclear staining, localized in a bright spots, which was displaced entirely by ankyrin or by high molecular weight microtubule-associated proteins (MAPs) from brain. In dividing cells, the punctate nuclear staining and the meshwork disappeared. Fluorescence was localized at the spindle pole during metaphase and was redistributed to the cleavage furrow in later stages of mitosis. An immunoreactive Mr 370,000 polypeptide comigrating with MAP1 was identified in brain extracts and copolymerized with microtubules through repeated cycles of polymerization and depolymerization. Finally, erythrocyte ankyrin associated with microtubules prepared from pure tubulin, and this binding was displaced by brain MAPs.

Ankyrins↗