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L A Fox

Publications and source records attributed to L A Fox.

At least 37 records · Page 2Linked to original sources
PubMed1992

The alpha subunit of sea urchin sperm outer arm dynein mediates structural and rigor binding to microtubules.

Glass-adsorbed intact sea urchin outer arm dynein and its beta/IC1 subunit supports movement of microtubules, yet does not form a rigor complex upon depletion of ATP (16). We show here that rigor is a feature of the isolated intact outer arm, and that this property subfractionates with its alpha heavy chain. Intact dynein mediates the formation of ATP-sensitive microtubule bundles, as does the purified alpha heavy chain, indicating that both particles are capable of binding to microtubules in an ATP-sensitive manner. In contrast, the beta/IC1 subunit does not bundle microtubules. Bundles formed with intact dynein are composed of ribbon-like sheets of parallel microtubules that are separated by 54 nm (center-to-center) and display the same longitudinal repeat (24 nm) and cross-sectional geometry of dynein arms as do outer doublets in situ. Bundles formed by the alpha heavy chain are composed of microtubules with a center-to-center spacing of 43 nm and display infrequent, fine crossbridges. In contrast to the bridges formed by the intact arm, the links formed by the alpha subunit are irregularly spaced, suggesting that binding of the alpha heavy chain to the microtubules is not cooperative. Cosedimentation studies showed that: (a) some of the intact dynein binds in an ATP-dependent manner and some binds in an ATP-independent manner; (b) the beta/IC1 subunit does not cosediment with microtubules under any conditions; and (c) the alpha heavy chain cosediments with microtubules in the absence or presence of MgATP2-. These results suggest that the structural binding observed in the intact arm also is a property of its alpha heavy chain. We conclude that whereas force-generation is a function of the beta/IC1 subunit, both structural and ATP-sensitive (rigor) binding of the arm to the microtubule are mediated by the alpha subunit.

Adenosine Triphosphate↗
PubMed1992

An ethical dilemma: coding medical records for reimbursement.

Coding accuracy is difficult enough with inconsistent and incomplete medical records adding to the challenge. But since the HCFA implementation of DRGs in 1983 to determine Medicare payments, coding has taken on an ethical dimension. In this article Leslie Ann Fox discusses the causes underlying this dilemma and proposes some solutions.

Abstracting and Indexing↗
PubMed1990

The key is teamwork: making medical records information systems succeed.

Problems within an existing hospital information system can often hamper efforts of medical records personnel to perform chart completion, clinical abstracting, tracking, deficiency analysis and other essential tasks. Years of experience have enabled Leslie Ann Fox, consultant for Care Communications, Inc., to collect observations, and through them, recommend key success factors to make the system work well.

Efficiency↗
PubMed1988

Isolated beta-heavy chain subunit of dynein translocates microtubules in vitro.

Our goal was to assess the microtubule translocating ability of individual ATPase subunits of outer arm dynein. Solubilized outer arm dynein from sea urchin sperm (Stronglocentrotus purpuratus) was dissociated into subunits by low ionic strength buffer and fractionated by zonal centrifugation. Fractions were assessed by an in vitro functional assay wherein microtubules move across a glass surface to which isolated dynein fractions had been absorbed. Microtubule gliding activity was coincident with the 12-S beta-heavy chain-intermediate chain 1 ATPase fractions (beta/IC1). Neither the alpha-heavy chain nor the intermediate chains 2 and 3 fractions coincided with microtubule gliding activity. The beta/IC1 ATPase induced very rapid gliding velocities (9.7 +/- 0.88 micron/s, range 7-11.5 micron/s) in 1 mM ATP-containing motility buffers. In direct comparison, isolated intact 21-S outer arm dynein, from which the beta/IC1 fraction was derived, induced slower microtubule gliding rates (21-S dynein, 5.6 +/- 0.7 micron/s; beta/IC1, 8.7 +/- 1.2 micron/s). These results demonstrate that a single subdomain in dynein, the beta/IC1 ATPase, is sufficient for microtubule sliding activity.

Adenosine Triphosphatases↗
PubMed1987

Direction of force generated by the inner row of dynein arms on flagellar microtubules.

Our goal was to determine the direction of force generation of the inner dynein arms in flagellar axonemes. We developed an efficient means of extracting the outer row of dynein arms in demembranated sperm tail axonemes, leaving the inner row of dynein arms structurally and functionally intact. Sperm tail axonemes depleted of outer arms beat at half the beat frequency of sperm tails with intact arms over a wide range of ATP concentrations. The isolated, outer arm-depleted axonemes were induced to undergo microtubule sliding in the presence of ATP and trypsin. Electron microscopic analysis of the relative direction of microtubule sliding (see Sale, W. S. and P. Satir, 1977, Proc. Natl. Acad. Sci. USA, 74:2045-2049) revealed that the doublet microtubule with the row of inner dynein arms, doublet N, always moved by sliding toward the proximal end of the axoneme relative to doublet N + 1. Therefore, the inner arms generate force such that doublet N pushes doublet N + 1 tipward. This is the same direction of microtubule sliding induced by ATP and trypsin in axonemes having both inner and outer dynein arms. The implications of this result for the mechanism of ciliary bending and utility in functional definition of cytoplasmic dyneins are discussed.

Adenosine Triphosphatases↗
PubMed1984

The influence of fibroblast-like cells derived from canine fetal hematopoietic tissues on the regulation of lymphohematopoiesis.

Media conditioned by fibroblast-like cells derived from organs active in fetal lymphohematopoiesis were studied for their effects on adult granulocyte/macrophage colony-forming units (CFU-GM). Fibroblasts from fetal liver produced a factor stimulatory for CFU-GM, whereas fibroblasts from fetal marrow produced a factor inhibitory for CFU-GM which was not completely relieved by adding indomethacin to the assay. Our studies indicated that neither fetal marrow nor fetal liver produced factors affecting lymphocyte colony-forming units (CFU-L). Cell-cell interactions between fibroblast-like cells derived from fetal liver or marrow and normal adult CFU-GM were also studied. We observed that fibroblasts derived from both fetal and adult marrow inhibited colony formation, whereas inhibition in the presence of fetal liver fibroblasts was minimal. Loss of inhibitory activity by a liver fibroblast cell line over repeated passages was seen. Differential analysis of colonies formed above an adherent layer of fetal marrow fibroblasts suggested that these fibroblasts suppress myeloid/macrophage differentiation to a far greater degree than did adult marrow fibroblasts. A role in the regulation of fetal lymphohematopoiesis may be played by stromal fibroblasts.

Animals↗
PubMed1983

Characterization of canine fetal lymphohematopoiesis: studies of CFUGM, CFUL, and CFUF.

We assayed the colony forming units for granulocyte-macrophages (CFUGM), T-lymphocytes (CFUL) and fibroblasts (CFUF) in the blood, bone marrow, liver and spleen of the canine at 45 and 55 days of gestation and 4 and 30 days post partum. As the number of CFUGM per 5 x 10(5) cells increased in the fetal liver, the number of CFUGM increased in circulating blood, whereas when the number of CFUGM decreased in liver and blood, CFUGM increased in both bone marrow and spleen. This suggests that CFUGM are produced in the liver, are released into the circulation and then transported to the spleen and bone marrow. CFUF studies showed that canine fetal bone marrow and spleen are active sites of fibroblast proliferation, whereas the liver is not. Morphologic examination of colonies derived from concanavalin-A stimulated progenitors ("CFUL") demonstrated that these colonies from fetal tissues and adult bone marrow were not exclusively lymphoid but were also made up of significant numbers of precursors of the myeloid and monocytic series. Lymphocyte stimulation tests (LST) showed the presence of a large population of mitogen-independent dividing cells, suggesting that fetal lymphohematopoiesis may be at least partially under the influence of factors other than those of adult cells.

Animals↗