ABSTRACT
Packaging materials are often considered a critical control point in HACCP systems of food companies. Methods for the determination of the microbial contamination rate of plastic cups, especially for dairy products, must reliably detect single moulds, yeasts or coliforms. In this study, a comparison of a specially adapted coating method, impedance method, direct inoculation and membrane filter technique was carried out to determine contamination with yeasts, moulds, coliforms and total bacterial counts using the appropriate agar in each case. The coating method is recommended for determining yeasts, moulds and coliforms as it allows the localization of the microorganisms as well as the determination of single microorganisms. For total bacterial count, a direct inoculation technique is proposed. The employing of simple measures in the production and during transport of packaging materials, such as dust-prevention or tight sealing in polyethylene bags, heavily reduces microbial contamination rates of packaging material. To reduce contamination rates further, electron beam irradiation was applied: plastic cups sealed in polyethylene bags were treated with 4-5 kGy, a dose that already leads to sterile polystyrene and polypropylene cups without influencing mechanical characteristics of the packaging material.
Subject(s)
Dairy Products/microbiology , Electrons , Equipment Contamination , Food Packaging/methods , Sterilization/methods , Alternaria/isolation & purification , Alternaria/radiation effects , Escherichia coli/isolation & purification , Escherichia coli/radiation effects , Food Contamination/prevention & control , Humans , Polypropylenes/chemistry , Polypropylenes/radiation effects , Polystyrenes/chemistry , Polystyrenes/radiation effectsABSTRACT
The enantiomers of 40 basic analytes, mostly pharmaceuticals, were separated by nonaqueous capillary electrophoresis in acidic methanol background electrolytes using the sodium salt of heptakis(2,3-dimethyl-6-sulfato)-beta-cyclodextrin (HDMS-beta-CD). The effective mobilities, separation selectivities, and peak resolution values were determined as a function of the HDMS-beta-CD concentration in the 0-40 mM range and were found to follow the theoretical predictions of the charged resolving agent migration model (CHARM model). Fast, efficient enantiomer separations were achieved for a large number of both very hydrophobic and hydrophilic weak bases.
Subject(s)
Cyclodextrins/chemistry , Electrophoresis, Capillary/methods , beta-Cyclodextrins , StereoisomerismABSTRACT
We present and study the behavior of a simple kinetic model for the melting of RNA secondary structures, given that those structures are known. The model is then used as a map that assigns structure dependent overall rate constants of melting (or refolding) to a sequence. This induces a "landscape" of reaction rates, or activation energies, over the space of sequences with fixed length. We study the distribution and the correlation structure of these activation energies.
Subject(s)
RNA/chemistry , Base Sequence , Chemical Phenomena , Chemistry, Physical , Escherichia coli/chemistry , Kinetics , Models, Biological , Molecular Sequence Data , Nucleic Acid Conformation , RNA, Bacterial/chemistry , RNA, Transfer, Phe/chemistry , Statistics as Topic , TemperatureABSTRACT
We have investigated the expression of intercellular adhesion molecule-1 (ICAM-1) by novel functional human thyroid cell lines (designated SGHTL). ICAM-1 is constitutively expressed and it is rapidly upregulated in response to each of the recombinant cytokines: gamma-interferon, interleukin-1 and tumour necrosis factor. This contrasts with the more slowly increased expression of major histocompatibility complex (MHC) class II antigens in response to gamma-interferon alone. We have also demonstrated binding of activated lymphocytes to SGHTL cells: this interaction is increased following treatment with these cytokines and is inhibited by monoclonal antibodies directed against ICAM-1 or lymphocyte function-associated antigen-1 (LFA-1) but not by antibodies against CD2 or MHC class II antigens. Hence, we conclude that the binding of lymphoblasts to human thyroid cells involves an LFA-1- and ICAM-1-dependent pathway as well as other basal and cytokine-inducible pathway(s). These do not appear to involve MHC class II antigens, CD2 or an LFA-1 ligand other than ICAM-1.
Subject(s)
Cell Adhesion Molecules/physiology , Lymphocytes/metabolism , Thyroid Gland/metabolism , Antibodies, Monoclonal/pharmacology , Antigens, Differentiation/immunology , Antigens, Differentiation/physiology , Cell Adhesion , Cell Adhesion Molecules/immunology , Cell Line , Histocompatibility Antigens Class II/metabolism , Humans , Intercellular Adhesion Molecule-1 , Interferon-gamma/pharmacology , Interleukin-1/pharmacology , Kinetics , Lymphocyte Function-Associated Antigen-1 , Receptors, Leukocyte-Adhesion/immunology , Receptors, Leukocyte-Adhesion/physiology , Recombinant Proteins/pharmacology , Tumor Cells, Cultured , Tumor Necrosis Factor-alpha/pharmacologyABSTRACT
We propose that many potential pitfalls of a research study can be brought to light through the exercise of writing a zeroth draft of the paper before beginning formal data collection. Further, because the zeroth draft of the paper contains the elements required in most research proposals--background, rationale, approach to data analysis, methods, and significance--it may serve as a generic grant application that can be easily recast in the style required by a specific funding agency. Moreover, the task of preparing the final report after completing the study is a shorter, less painful process if one has only to revise the zeroth draft rather than face the blank page. In these ways writing the scientific paper before gathering the data can help an investigator plan, fund, execute, and report a study that asks and answers specific and important questions.
