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Howard M Shapiro

Publications and source records attributed to Howard M Shapiro.

7 recordsLinked to original sources
PubMed2006

Personal cytometers: slow flow or no flow?

BACKGROUND: Although some manufacturers have optimistically described instruments with prices in the 40,000 US dollars range as "personal cytometers", analogy with the personal computer suggests that the target price for a true "personal" cytometer should be under 5,000 US dollars. Since such an apparatus could find a wide range of applications in cytomics in both developing and developed countries, it seemed desirable to consider its technical and economic feasibility. METHODS: Using resolution targets and a variety of fluorescent bead standards immobilized on filters and/or slides, we evaluated high-intensity LEDs as fluorescence excitation sources, relatively inexpensive CCD cameras as detectors, and 35 mm camera lenses and plastic low-power microscope optics for light collection in a simple, inexpensive low-resolution imaging cytometer. RESULTS: The components tested could be combined toproduce an instrument capable of detecting fewer than 10,000 molecules of cell-associated fluorescent label, and thus applicable to a broad range of cytometric tasks. CONCLUSIONS: Given the requirements for light sources, detectors, optics, mechanics, electronics and data analysis hardware and software, and the components presently available, it should be easier to reach the desired 5,000 US dollars price point with an image cytometer than with a flow cytometer.

Flow Cytometry↗
PubMed2004

"Cellular astronomy"--a foreseeable future in cytometry.

Advances in electro-optic technology within the past 2 years, notably the development of high-intensity light-emitting diodes and highly efficient charge-coupled device cameras, have made it feasible to produce small, simple, rugged, automated fluorescence image cytometers, with selling prices well below 10,000 US dollars, that can make measurements previously the exclusive domain of flow and scanning cytometers costing many times more. It should be feasible to apply the new cytometric technology in scientific and geographic areas for which a previous generation of instruments was too complex and too expensive, e.g., to problems of diagnosis and management of infectious diseases prevalent at critical levels in resource-poor areas, such as the human immunodeficiency virus, malaria, and tuberculosis.

Cell Separation↗
PubMed2004

Multiparameter flow cytometry of bacteria.

The small size of bacteria makes some microbial constituents undetectable or measurable with only limited precision by flow cytometry. Bacteria may also behave differently from eukaryotes in terms of their interaction with dyes, drugs, and other reagents. It is therefore difficult to design multiparameter staining protocols that work, unmodified, across a wide range of bacterial species. This chapter describes reliable flow cytometric methods for assessment of the physiologic states of Gram-negative organisms, on the one hand, and Gram-positive organisms, on the other, based on measurement of membrane potential and membrane permeability. These techniques are useful in the assessment of effects of environmental conditions and antimicrobial agents on microorganisms.

Anti-Infective Agents↗
PubMed2003

Correlation of daptomycin bactericidal activity and membrane depolarization in Staphylococcus aureus.

The objective of this study was to further elucidate the role of membrane potential in the mechanism of action of daptomycin, a novel lipopeptide antibiotic. Membrane depolarization was measured by both fluorimetric and flow cytometric assays. Adding daptomycin (5 micro g/ml) to Staphylococcus aureus gradually dissipated membrane potential. In both assays, cell viability was reduced by >99% and membrane potential was reduced by >90% within 30 min of adding daptomycin. Cell viability decreased in parallel with changes in membrane potential, demonstrating a temporal correlation between bactericidal activity and membrane depolarization. Decreases in viability and potential also showed a dose-dependent correlation. Depolarization is indicative of ion movement across the cytoplasmic membrane. Fluorescent probes were used to demonstrate Ca(2+)-dependent, daptomycin-triggered potassium release from S. aureus. Potassium release was also correlated with bactericidal activity. This study demonstrates a clear correlation between dissipation of membrane potential and the bactericidal activity of daptomycin. A multistep model for daptomycin's mechanism of action is proposed.

Anti-Bacterial Agents↗
PubMed2002

Report from a workshop on multianalyte microsphere assays.

Multiplexed assays using fluorescent microspheres is an exciting technique that has been gaining popularity among researchers, particularly those in the public health field. Part of its popularity is due to its flexibility, as both immunoassays and oligonucleotide hybridization assays can be developed on this platform. This report summarizes a workshop held by the Centers for Disease Control and Prevention that discussed issues surrounding these assays and the Luminex 100 xMAP instrument. Topics included instrumentation, assay design, sample matrix and volume, quality control, and development of commercial applications.

Animals↗