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Biomedical subjects

J Feder

Publications and source records attributed to J Feder.

At least 109 records · Page 6Linked to original sources
PubMed1983

Multiple DNA fragment polymorphisms associated with immunoglobulin mu chain switch-like regions in man.

DNA probes containing the switch region (S) associated with the human immunoglobulin heavy chain mu gene were used to investigate polymorphisms in the germ-line human DNA. Six polymorphisms, detected by a single restriction enzyme (Sst I) are described. Linkage studies in 29 families show that five of the six polymorphisms, although relatively unassociated in random individuals, segregate in complete linkage one to the other and to Gm allotypes (markers on the heavy chain of IgG), while the sixth segregates independently. Altogether, when one considers the DNA markers at the five closely linked loci and the IgG1 and IgG3 heavy chain allotypes, 33 different haplotypes have been described; of these, 28 are detected by the DNA polymorphism alone. Study of 158-187 random haplotypes showed strong linkage disequilibrium only between one DNA polymorphism (Sst A) and Gm. Of the polymorphic Sst I loci, one, Sst E [associated with 2.2- to 2.7-kilobase (kb) fragments], is included in the mu chain S region (S mu); another, Sst A (6.8-7.4 kb), must be very close to the gamma 1-gamma 3 chain gene cluster. Based on studies of an IgE human myeloma, a third polymorphism, Sst C (4.8-5.5 kb), should map 3' of the active epsilon chain gene. An Sst I restriction enzyme map of phage clones carrying the two alpha chain genes indicates that Sst A and Sst C loci probably overlap with the alpha 1 and alpha 2 S regions, respectively. Both deletion/duplications and point mutations were detected.

Chromosome Deletion↗
PubMed1983

A DNA polymorphism in close physical linkage with the proopiomelanocortin gene.

Cellular DNAs from a panel of 20 unrelated individuals were screened for restriction fragment length polymorphisms (RFLP) with a DNA probe containing the first exon of the proopiomelanocortin gene (POMC), which has been assigned to chromosome 2p23-25. Digestion with the restriction endonuclease Sst 1 revealed a high frequency RFLP. The two alleles that were found are fragments of 10- and 15-kilobase (kb) length and are in Hardy-Weinberg equilibrium with frequencies of 72.6% and 27.4%, respectively. Informative families were tested for linkage between POMC/Sst 1 RFLP and other polymorphic markers of chromosome 2. Linkage was excluded to AcP-1 (2p23-25) at 15% recombination, which is still consistent with the chromosomal assignments for these genes. The close physical linkage (10 kb) of the polymorphic locus to the POMC gene makes this RFLP a suitable marker for future linkage studies involving the POMC gene.

Chromosome Mapping↗
PubMed1982

Medicare's nursing-home benefit: variations in interpretation.

The use of skilled-nursing facilities by Medicare beneficiaries as measured in days of care per thousand elderly persons varies considerably from one state to another. To explore the possibility that this variation reflects differences in the administrative interpretation of rules governing coverage, we developed nine hypothetical cases and presented them by telephone to claims reviewers in fiscal intermediaries and professional standards review organizations. Cases were designed to illuminate the reviewers' use of discretion. We observed marked differences both in the reviewers' decisions to cover or not cover patients and in the reasoning behind their decisions. Three of the 18 reviewers decided to cover very few cases; almost half the reviewers decided to cover most of the cases, but not the same ones. In only two cases did the 18 reviewers approach consensus. This variation is a reflection of the complexity of Medicare's coverage rules and its decentralized administration. To reduce variation, we recommend more centralized review with oversight by Medicare's central office rather than by its 10 regional offices. This oversight should include the training of reviewers in a way that focuses on complex cases to improve the consistency of judgment.

Eligibility Determination↗
PubMed1982

An assay measuring the stimulation of several types of bovine endothelial cells by growth factor(s) derived from cultured human tumor cells.

Endothelial cell growth factor(s) from several previously untested human tumor cell lines (i.e., SK-HEP-1, MG63, A375, TE671-C1, RD) were detected using a low cell inoculum growth assay. The final cell density in the 2-cm2 wells was determined by a highly sensitive DNA content measurement performed directly in the tissue culture plates. The sensitivity of the assay to human tumor cell growth factors depended critically on the low cell inocula, 2,000 to 5,000 cells/well. Most of the bovine endothelial cells used were cloned from primary cultures; all the cell lines obtained from various fetal and nonfetal sources responded to the growth factor(s) (up to a 16x stimulation) as well as to endothelial cell growth supplement. Dose response curves showing the cell specific response of bovine endothelial cells were obtained. The growth stimulatory activity and the in vivo chick embryo chorioallantoic membrane assay responses correlated sufficiently to imply that the assay is detecting tumor angiogenesis factor or some closely related activity. This in vitro assay should prove useful in the identification and purification of tumor-derived factors and in the elucidation of the role of these factors in the events comprising angiogenesis.

Animals↗
PubMed1981

Large-scale rotating filter perfusion system for high-density growth of mammalian suspension cultures.

A system has been developed for growth and maintenance of mammalian cells in suspension culture at high density. In principle, the maintenance of constant levels of required nutrients coupled with the removal of toxic cell byproducts can support much higher suspension cell densities than may be obtained in conventional spinners. The system consisted of 4- or 40-liter reaction vessels equipped with a vertically supported rotating cylindrical filter. Agitation was provided by the magnetically driven, rotating filter. Fresh medium was supplied at a rate of 10 to 20 ml/h per 10(9) cells and the expended medium free of cells was withdrawn through the rotating filter. Both pH and dissolved O2 and CO2 were monitored and regulated. Walker 256 carcinosarcoma cells have been grown in these reactors to densities 10- to 30-fold greater than that obtained in Bellco spinners. In addition to high cell densities, the yield of cells per liter of medium used was 2- to 3-fold that obtained in the conventional systems. Both 4- ad 40-liter reactor also has been operated without the use of antibiotics. The 40-liter reactor also has been modified for chemostat operation. In a single run, for example, the Walker cell density was maintained between 6 and 10 x 10(6) cells/ml with a total yield of 8.7 x 10(11) cells from 360 liters of medium.

Animals↗
PubMed1980

Cell aggregate suspension culture for large-scale production of biomolecules.

A method is described for the rapid reversible conversion of a number of continuous cell lines from anchorage-dependent growth to growth as aggregates of cells in suspension culture. Employing this technique, an inoculum of three 75-cm2 flasks of BALB/c SV3T3 cells was grown to 60 liters of aggregate suspension in 14 days. This yielded 120 ml of packed cells or 9.1 x 10(10) cells. Similar results were obtained for other cell lines. Biomolecules such as migration-inhibition factor (MIF) and plasminogen activator were produced from these cultures.

Animals↗
PubMed1980

Regulating the bed supply in nursing homes.

Federal and state regulation of capital expenditures has been advanced as a means both to ensure rational allocation of resources and to control costs. But evidence drawn from eight states suggests that limiting the supply of nursing home beds ("certificate of need"), without refining conflicting standards of eligibility, quality control, and reimbursement policies (Medicaid and "rate-setting"), effectively discriminates against persons most in need of medical care. Alternative strategies for achieving economy, equity, and efficiency are explored.

Certificate of Need↗
PubMed1979

The politics of hospital payment.

This paper analyzes the politics of hospital payment over the last decade. The authors explain how provider interests and judgments became a standard for appropriate hospital payment: the impact of that standard on hospital costs; and the political obstacles to imposing an alternative standard and controlling hospital costs. The authors draw lessons from this experience, here and in other countries, to propose an alternative approach to hospital payment that would allow policymakers, accountable to the public, to make explicit choices about the level and nature of hospital expenditures.

Accounts Payable and Receivable↗