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Biomedical subjects

F Levin

Publications and source records attributed to F Levin.

6 recordsLinked to original sources
PubMed1991

Stimulation of megakaryocytopoiesis in mice by human recombinant interleukin-6.

The in vivo effects of purified human recombinant interleukin-6 (IL-6) on murine megakaryocytopoiesis were examined. IL-6 was administered subcutaneously to Swiss Webster mice, followed by evaluation of bone marrow megakaryocyte ploidy, size and frequency, and median platelet volume 24, 48, and 72 hours after the initiation of IL-6 administration. In addition, bone marrow megakaryocyte morphology was examined using electron microscopy at 72 hours. IL-6 (10,000 U per subcutaneous injection) was administered three times during the first 24 hours, three times during the second 24 hours, and twice during the last 24-hour period. IL-6 bioactivity (10 U/ng) was determined using the IL-6-dependent murine hybridoma cell line B9. Megakaryocyte ploidy distribution, measured by two-color flow cytometry, demonstrated a shift in the modal ploidy class from 16N to 32N and a significant increase in the relative frequency of 64N megakaryocytes 48 and 72 hours (but not 24 hours) after initiation of IL-6 administration (cumulative doses of 60,000 and 80,000 U at 48 and 72 hours, respectively). In addition, ploidy levels were increased in animals that received a cumulative IL-6 dose of only 40,000 U (evaluated after 72 hours). The size of recognizable bone marrow megakaryocytes, determined by the cross-sectional areas of plastic embedded bone marrow megakaryocytes, was increased at the 48-hour (60,000 U IL-6) and 72-hour (80,000 U IL-6) time points. Megakaryocyte frequency, measured by flow cytometry, was unaffected at all time points and doses of IL-6. Median platelet volume, measured by electrical impedance, was not consistently altered by administration of IL-6. Electron microscopic examination of bone marrow megakaryocytes showed an increase in the proportion of megakaryocytes with a wide, peripheral, organelle-deficient zone from 20% +/- 9% (SD) in control animals to 50% +/- 7% (SD) (P less than .02) in animals that received IL-6. No changes were observed in the distribution of the demarcation membranes. IL-6 is a potent stimulator of murine megakaryocytopoiesis, in vivo, and appears to act early in megakaryocyte differentiation.

Animals↗
PubMed1987

Thrombocytopoietic response to immunothrombocytopenia in nude mice.

Thrombocytopoiesis was evaluated in T cell-deficient nu/nu mice and in T cell-replete nu/+ controls to determine if abnormalities would be associated with the deficiency of T cells. Mice were studied in the unperturbed steady state and after acute immunothrombocytopenia was induced by an injection of guinea pig antimouse platelet serum (APS). The state of thrombocytopoiesis was determined from platelet counts, megakaryocyte size, megakaryocyte number, and numbers of Meg-CFC. Splenic lymphocytes were evaluated by response to the mitogens bacterial lipopolysaccharide (LPS), phytohemagglutinin (PHA), and concanavalin A (Con A). Hematocrits, reticulocyte counts, leukocyte counts, marrow cellularity, GM-CFC, and BFU-E also were measured. Steady state thrombocytopoiesis was identical in nu/nu and nu/+ mice. In response to an injection of APS, acute thrombocytopenia was followed by macromegakaryocytosis and rebound thrombocytosis in mice of both genotypes. Splenic Meg-CFC increased in nude mice after APS or an injection of normal guinea pig serum (NGpS), and splenic GM-CFC increased after APS. Neither Meg-CFC nor GM-CFC increased in the spleens of nu/+ mice, but they showed early transient increases in bone marrow that did not occur in nu/nu mice. Sporadic, but weak, mitogenic responses to PHA or Con A were occasionally observed with nu/nu spleen cells, but these did not correlate with the state of thrombocytopoiesis. The results demonstrated that platelet production was normal in nu/nu mice and that megakaryocytopoiesis and platelet production responded to the stimulus imposed by acute immunothrombocytopenia. Increases in megakaryocyte size and platelet production occurred independently of changes in numbers of Meg-CFC, GM-CFC, or BFU-E. A normal complement of T cells appears to be unnecessary for normal platelet production and its augmentation in response to the stimulus of acute immunothrombocytopenia in vivo.

Animals↗
PubMed1987

Multivariate flow cytometric characterization and enrichment of murine megakaryocyte progenitors (CFU-Meg).

Multivariate flow cytometric analysis and sorting of mouse bone marrow cells viably stained with Hoechst 33342 (HO) was utilized to obtain a subpopulation enriched at least 30- to 60-fold for clonogenic megakaryocyte precursors (CFU-Meg). HO fluorescence intensity, forward light scatter, and perpendicular light scatter were measured on each HO-stained bone marrow cell as it passed through a dual beam flow cytometer. Cells were sorted on the basis of their light scattering and HO fluorescence intensity properties. The sorting region which included cells with high forward light scatter, low perpendicular light scatter, and low (0.1-0.65 times the modal channel) HO fluorescence intensity contained approximately 0.6% CFU-Meg. Of all CFU-Meg, 75% were contained in the light scatter gate, and 56% of all CFU-Meg were in the low HO-sorting region. This technique offers a simple, one-step procedure to obtain preparations enriched in murine clonogenic megakaryocyte precursors.

Animals↗
PubMedDate not supplied

Exploring performance issues for a clinical database organized using an entity-attribute-value representation.

BACKGROUND: The entity-attribute-value representation with classes and relationships (EAV/CR) provides a flexible and simple database schema to store heterogeneous biomedical data. In certain circumstances, however, the EAV/CR model is known to retrieve data less efficiently than conventionally based database schemas. OBJECTIVE: To perform a pilot study that systematically quantifies performance differences for database queries directed at real-world microbiology data modeled with EAV/CR and conventional representations, and to explore the relative merits of different EAV/CR query implementation strategies. METHODS: Clinical microbiology data obtained over a ten-year period were stored using both database models. Query execution times were compared for four clinically oriented attribute-centered and entity-centered queries operating under varying conditions of database size and system memory. The performance characteristics of three different EAV/CR query strategies were also examined. RESULTS: Performance was similar for entity-centered queries in the two database models. Performance in the EAV/CR model was approximately three to five times less efficient than its conventional counterpart for attribute-centered queries. The differences in query efficiency became slightly greater as database size increased, although they were reduced with the addition of system memory. The authors found that EAV/CR queries formulated using multiple, simple SQL statements executed in batch were more efficient than single, large SQL statements. CONCLUSION: This paper describes a pilot project to explore issues in and compare query performance for EAV/CR and conventional database representations. Although attribute-centered queries were less efficient in the EAV/CR model, these inefficiencies may be addressable, at least in part, by the use of more powerful hardware or more memory, or both.

Database Management Systems↗