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Biomedical subjects

B H Davis

Publications and source records attributed to B H Davis.

At least 91 records · Page 5Linked to original sources
PubMed1987

Specific adsorption of HTLV-I to various target human and animal cells.

In this report, we describe a flow cytometric analysis of HTLV-I specific binding to fresh and cultured cells on a single cell basis. This assay uses rhodamine hydrocarbon tagged, purified HTLV-I virions according to the procedure originally described for avian retroviruses. Successful HTLV-I transmission was detected by analysis of integrated HTLV-I DNA, virion-associated reverse transcriptase, and/or intracellular HTLV-I core antigen p19 expression. Only a specific virus-cell interaction was detected because nonrhodamine-tagged homologous virus or related HTLV-II interfered with tagged HTLV-I binding. In contrast, an unrelated, nonlabeled animal retrovirus was unable to block tagged HTLV binding. Of the cell lines tested, 2 nonlymphoid mammalian and 3 human lymphoid bound significantly high to moderate levels of HTLV-I-tagged virions. The other three human lymphocyte cell lines were insensitive to HTLV-I adsorption. A direct correlation was observed between HTLV-I binding sites and infectivity of human lymphoid cells alone and not other nonlymphoid animal cells. Fresh normal human mononuclear cells bound low levels of HTLV-I virions. As expected, T lymphocytes demonstrated more binding than did the non-T cell population. Enhancement of HTLV-I cell binding in a subpopulation of mononuclear target cells was achieved with phytohemagglutinin (PHA) activation and interleukin 2 (IL2) stimulation, which correlates well with previously published infectivity studies.

Cell Line↗
PubMed1986

Characterization of f-Met-Leu-Phe-stimulated fluid pinocytosis in human polymorphonuclear leukocytes by flow cytometry.

N-formylated chemotactic peptide stimulation of human neutrophils initiates a number of cellular processes, such as lysosomal enzyme release and superoxide anion production, that are indicative of the events of neutrophil activation during the acute inflammatory response in disease. This study characterizes a newly recognized neutrophil activation event, N-formylated chemotactic peptide-stimulated fluid pinocytosis in human neutrophils, using a novel flow cytometric assay for this activity. Fluid pinocytosis was found to be inhibited by acidic pH and low temperature but could be enhanced by cytochalasin B treatment or surface adherence by neutrophils. The activity measured by this new assay of fluid pinocytosis appears to be separate and distinct from lysosomal enzyme release and receptor-mediated adsorptive endocytosis in neutrophils. The physiologic significance of N-formylated chemotactic peptide-stimulated fluid pinocytosis is not known, but a possible relationship to neutrophil locomotion is discussed.

Body Fluids↗
PubMed1985

Membrane and cytoskeletal changes associated with IgE-mediated serotonin release from rat basophilic leukemia cells.

Binding of antigen to IgE-receptor complexes on the surface of RBL-2H3 rat basophilic leukemia cells is the first event leading to the release of cellular serotonin, histamine, and other mediators of allergic, asthmatic, and inflammatory responses. We have used dinitrophenol-conjugated bovine serum albumin (DNP-BSA) as well as the fluorescent antigen, DNP-B-phycoerythrin, and the electron-dense antigen, DNP-BSA-gold, to investigate dynamic membrane and cytoskeletal events associated with the release of [3H]serotonin from anti-DNP-IgE-primed RBL-2H3 cells. These multivalent antigens bind rapidly to cell surface IgE-receptor complexes. Their distribution is initially uniform, but within 2 min DNP-BSA-gold is found in coated pits and is subsequently internalized. Antigen internalization occurs in the presence and absence of extracellular Ca2+. The F-actin content of the detergent-extracted cell matrices analyzed by SDS PAGE decreases during the first 10-30 s of antigen binding and then increases by 1 min to almost double the control levels. A rapid and sustained increase is also observed when total F-actin is quantified by flow cytometry after binding of rhodamine-phalloidin. The antigen-stimulated increase in F-actin coincides with (and may cause) the transformation of the cell surface from a finely microvillous to a highly folded or plicated topography. Other early membrane responses include increased cell spreading and a 2-3-fold increase in the uptake of fluorescein-dextran by fluid pinocytosis. The surface and F-actin changes show the same dependence on DNP-protein concentration as stimulated [3H]serotonin release; and both the membrane responses and the release of mediators are terminated by the addition of the non-cross-linking monovalent ligand, DNP-lysine. These data indicate that the same antigen-stimulated transduction pathway controls both the membrane/cytoskeletal and secretory events. However, the membrane and actin responses to IgE-receptor cross-linking are independent of extracellular Ca2+ and are mimicked by phorbol myristate acetate, whereas ligand-dependent mediator release depends on extracellular Ca2+ and is mimicked by the Ca2+ ionophore A23187.

Actin Cytoskeleton↗
PubMed1983

Tubulointerstitial nephropathy associated with arteriohepatic dysplasia.

An infant with a variant of arteriohepatic dysplasia (characteristic facies, valvular and peripheral pulmonic stenosis, hypercholesterolemia, intrahepatic cholestasis) and a severe tubulointerstitial nephropathy is described. Liver biopsy at 2 mo and at 10 mo of age revealed marked hepatocellular cholestasis and a slight decrease in the number of interlobular bile ducts per portal triad. Severe fibrosis was noted at 10 mo. Renal findings included tubular atrophy, microcystic tubular dilatation, and interstitial fibrosis. Death at 10 mo was associated with renal failure and pneumonia. The case suggests an additional association between renal cystic disease and abnormalities of the biliary tree.

Biopsy↗
PubMed1982

Membrane activity and topography of F-Met-Leu-Phe-Treated polymorphonuclear leukocytes. Acute and sustained responses to chemotactic peptide.

The chemotactic peptide N-formylmethionyl-leucyl-phenylalanine (f-Met-Leu-Phe) causes a dramatic stimulation of membrane ruffling and a fluid pinocytosis in polymorphonuclear leukocytes (PMNs). These responses are maximal by 1 minute and subside within 5-10 minutes. The same immediate responses characterize cells exposed to several peptide hormones and may thus represent an essential component of target cell activation by peptides. The stimulation of the whole membrane following f-Met-Leu-Phe binding is succeeded by the development of a polarized cell shape with a posterior uropod and a broad anterior lamellipodium, both subtended by microfilaments. Membrane components and functions segregate into distinct domains on polarized PMNs. Thus, succinyl concanavalin A-receptor complexes are capped and internalized by receptor-mediated endocytosis at the uropod; the uptake by fluid pinocytosis of fluorescein-dextran is restricted to the uropod; and coated pits and coated vesicles are concentrated at the uropod. The lamellipodium excludes coated pits and lacks pinocytic activity but shows preferential binding of immunoglobulin aggregates, presumably to Fc receptors. The origin and physiologic implications of these asymmetries of membrane molecular and functional topography on polarized cells are discussed.

Adsorption↗
PubMed1981

Adenosine deaminase activity in lymphoid subpopulations and leukemias.

Adenosine deaminase has been measured by the indirect spectrophotometric method in lymphoblasts from adult and pediatric lymphoblastic leukemias, peripheral T- and B-cells, mature T-cell leukemia (Sézary cell), and mitogen-stimulated peripheral control T- and B-cells. It was found that, if the specific activity of the enzyme is expressed in terms of cell cytoplasmic protein concentration rather than cell number, null-cell leukemia has enzyme levels markedly higher than T-cell lymphoblastic leukemic or Sézary cells. The range in values is far less than those reported by other authors using the direct spectrophotometric assay and cell number prior to lysis. Non-leukemic T- and B-cells from control individuals show minor differences as do T gamma-enriched cells. Lymphocytes from female oriental control populations were significantly lower. Both mitogen-stimulated lymphoblasts and control lymphocytes show similar elevations in adenosine deaminase activity so that no effect per se can be ascribed to lymphoblastic transformation.

Adenosine Deaminase↗
PubMedDate not supplied

The effect of retinol on Ito cell proliferation in vitro.

Hepatic sinusoidal fat-storing Ito cells are felt to represent the primary storage site for hepatic vitamin A and may be important collagen-producing effector cells during hepatic fibrogenesis. The cirrhotic liver generally has a decreased vitamin A content with increased numbers of "transitional" myofibroblasts adjacent to developing fibrous bands. It has been suggested that Ito cells "transform" into these myofibroblasts. The in vivo loss of Ito cell vitamin A can be simulated in vitro as Ito cells spontaneously lose their vitamin A lipid droplets during primary culture. The current study evaluated Ito cell proliferation in vitro with respect to vitamin A content and the extracellular collagen matrix. The cells were grown on a Type I or Type IV collagen matrix to simulate the types of collagens presumed to be present in the space of Disse. Initially it was observed that freshly isolated Ito cells begin to proliferate several days after isolation coincident with the decline of the vitamin A lipid droplets and a decrease in cellular retinyl palmitate. The proliferation rate for passaged Ito cells was similar on either matrix (on Type I collagen: T 1/2 = 2.2 +/- 1.1 days, n = 16; on Type IV collagen: T 1/2 = 3.3 +/- 1.4 days, n = 4; p less than 0.11). This proliferation rate remained constant through Cell Generation 16 and was similar to the rate for primary Ito cells in culture. To evaluate the possibility that primary Ito cell proliferation is causally related to the loss of vitamin A, Ito cells were re-exposed to an increased concentration of retinol in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Small cell neuroendocrine carcinoma of the urinary bladder: report of three cases with ultrastructural analysis.

Three cases of small cell neuroendocrine carcinoma of the urinary bladder were studied by light and electron microscopic techniques. Dense-core, membrane-bound granules were identified in the cytoplasm of all 3 cases, substantiating the light microscopic impression of a morphologic similarity to other neuroendocrine carcinomas, such as small cell (oat cell) carcinoma of the lung. Two of the three cases showed clinical evidence of distant metastases, suggesting an aggressive biologic potential of this tumor similar to oat cell carcinoma of the lung. A partial remission was induced in these 2 cases using chemotherapy protocols similar to the drug regimens for small cell (oat cell) carcinomas of the lung. Recognition of this distinct entity has important clinical implications regarding therapeutic approach.

Aged↗
PubMedDate not supplied

Performance evaluation of a hematology blood counter with five-part leukocyte differential capability.

The summarized data and other studies to date indicate that performance of the Pentra 60 is comparable to other hematology analyzers for all CBC and 5-Diff parameters. Comparative studies indicate good correlation for all the reportable CBC parameters, lymphocyte counts, and neutrophil counts with 24 hr stability on blood samples. Good intermethod correlations on monocyte and eosinophil counts were observed. Only basophil counts showed poor intermethod correlations, but this is expected on a statistical basis, and the counts are similar to those reported for other hematology analyzer performance studies. The combination of the MDSS and stepper motor fluidic system allows for low-volume blood sampling, compact size, and low operational noise level. The Pentra 60 is well suited for physician's office laboratories, medical clinics, small- or medium-size hospitals with less than 100 CBCs per day, and larger hospitals or reference laboratories that need back-up for a high-end automated hematology analyzer.

Blood Cell Count↗