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Three types of methods for bichromatic paper disk spectrophotometry are described and illustrated by the detailed presentation of procedures for the dosage of hemoglobin and protein (with some applications in virology), as well as for glucose determination. The general algorithms that would make possible the automation of these methods by means of programmable systems are presented.

A linear approximated model is presented that takes into account a local anisotropic distribution of scattered light within a turbid medium. Light intensity depends upon the distance from the boundary surface of the scattering centers, so that the probability of photon-chromophore interaction is a function of the distance. For the sake of simplicity it is assumed that there are only two main zones, corresponding to two probabilities of photon-chromophore interaction. In this form, the Kubelka-Munk theory fits the experimental data supplied by bichromatic photometry of nucleic acids on paper disks.

The bichromatic paper disk spectrophotometry ultramicromethod developed in the "Stefan S. Nicolau" Institute of Virology can be successfully applied to the study of viral and cellular nucleic acids. The main applications - succinctly presented in the review - refer to : the identification and spectral characterization of nucleic acids, their quantitative determination, the study of the helix - statistical coil transition, the evaluation of the degree of polymerization of single stranded polynucleotides, the study of the kinetics of chemical and enzymatic hydrolysis and the determination of RNase activity, e.g. in human serum, the demonstration of the interaction between nucleic acids and other molecules of biological interest (biopolymers, poly- and oligocations, etc.), the rapid characterization of the ion exchange capacity of chromatography papers and of a mobile phase of the water - alcohol - electrolyte type.

Bichromatic absorbance measurements on RNA-impregnated paper disks may be applied to the ultramicroanalytic evaluation of the ion exchange capacity (IEC) of different chromatography papers. A newly defined absorbance parameter and the curves of its variation in terms of IEC are used to this purpose.

Bichromatic spectrophotometry determinations were performed on Whatman chromatographic paper disks impregnated with rRNA solutions of different concentrations, at ionic strengths ranging from nearly 0 to 1.4 M. The disks consisted of cellulose, either native or modified (by grafting of carboxymethyl, phosphate, Ecteola or DEAE groups, or by loading with silica gel). The results demonstrate that: 1) there is a positive correlation between the absorbance enhancement by multiple light scattering and the nearness of the nucleic acid molecules in relation to the surface of cellulose fibrils; b) the action on absorbance of ionic strength and of other physical factors differs in terms of the electric charges and of the exposure of other groups that may interact with nucleic acids through hydrogen bonds or Van der Waals forces.

A bichromatic spectrophotometry study in the near UV spectral range was performed on paper disks impregnated with DNA and RNA in NaCl solutions of different concentrations. Absorbance curves plotted versus a NaCl molarity log-scale degree of polymerization and the solubility of the polynucleotide. The -a/b value, determined by a previously reported equation, appeared to be constant for a given nucleic acid, irrespective of the wavelength in the spectral range 205-280 nm. This phenomenon cannot be attributed to a heterogeneous macroscopic distribution of the nucleic acid throughout the disk.

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Résumé: De nombreuses études réalisées chez des patients hospitalisés en réanimation et considérés comme immunocompétents ont révélé de profondes altérations immunitaires favorisant les réactivations virales. Les réactivations de certains Herpesviridae (HSV et CMV) ont notamment été associées à une augmentation de la morbi-mortalité des patients de réanimation. Le diagnostic précoce de ces réactivations est donc de plus en plus recommandé dans la prise en charge du patient hospitalisé en réanimation, même si les indications de mise en route d'un traitement antiviral sont encore en évaluation. Plus récemment, l'exploration du virome humain, et notamment la part des Torque teno virus (TTV), a été proposée pour estimer le niveau d'immunocompétence dans des populations de patients immunodéprimés à risque d'infections virales opportunistes. Chez les patients transplantés d'organe, la proportion représentée par les TTV augmente avec le degré d'immunodépression et est associée à un risque augmenté d'infections secondaires. Ce marqueur reste à évaluer dans d'autres contextes de dysfonction immunitaire, notamment chez les patients intubés ventilés de réanimation. Plus largement, le développement des approches de métagénomique permettra d'étudier les modifications du virome humain en lien avec le contexte immunitaire, et pourrait être un outil innovant, surtout dans le contexte de l'introduction de molécules immunorégulatrices pour la prise en charge des complications de réanimation. Studies performed in patients considered as immunocompetent and hospitalized in intensive care unit (ICU) have revealed profound immune alterations leading to an increased risk of viral reactivations. In particular, Herpesviridae reactivations (HSV and CMV) have been associated with an increased morbidity and mortality in ICU patients. Early diagnosis of these reactivations is now recommended in ICU patients, but the indications of an antiviral therapy remain to be better defined. Advances in molecular biology now allow us to study the human virome in different biological compartments. Among the more frequent viruses detected in the virome, Torque Teno Virus (TTV) has been shown to be associated to the immunocompetence level of immunocompromised patients at risk of opportunistic viral infections. In organ transplant patients, the TTV proportion in blood increases with the degree of immunosuppression and the risk of secondary infections. It remains to be evaluated in other immune dysfunction settings, such as ICU patients. Human virome modulation, as measured by metagenomics, is a promising tool to investigate immune status in various clinical settings. It could be an innovative marker for personalized care, including the evaluation of immunomodulatory molecules use for the prevention and treatment of infectious complications in ICU patients. [ABSTRACT FROM AUTHOR]

Copyright of Virologie is the property of John Libbey Eurotext Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Influenza viruses are segmented negative-sense RNA viruses whose RNA dependant RNA polymerase (RdRp) multiple activities are central for the viral life cycle. The RdRp is composed of three subunits, PB1, PB2 and PA. It binds to the extremities of each vRNA segments encapsidated with multiple copies of the Nucleoprotein (NP), altogether constituting the viral ribonucleoproteins (vRNPs). The RdRp performs both vRNA transcription and replication in the context of vRNP in the nuclei of infected cells. The temporal regulation of RdRp-associated activities is essential for the successful completion of the virus life cycle, but its understanding has been limited by the lack of structural information about the polymerase complex. The atomic-resolution of polymerase complexes from influenza virus type A, type B and type C came out in the past two years. We compile here the data provided by the near-concomitant resolution of several influenza polymerase crystal structures. We will highlight how structural information can contribute to our understanding of the interactions between the RdRp and viral or host factors. [ABSTRACT FROM AUTHOR]

The results of over 200 scientific papers in the field of in vivo and in vitro virus--tumor relationships, worked out in the "Stefan S. Nicolau" Institute of Virology during a period of over 25 years, are very briefly reviewed. Stress is laid on the original theoretical and practical contributions of the institute to the knowledge of viral carcinogenesis in animals and humans. Some personal viewpoints in the interpretation of results are presented and new research prospects in this field--which represents a traditional concern of the institute--are lutlined.

RNA absorbances Ad were determined by bichromatic spectrophotometry at 240, 260 and 280 nm, versus 350 nm values, on paper disks containing different 2-propanol concentrations and NaCl amounts. No significant differences in terms of the NaCl content could be observed at alcohol concentrations higher than 70%; the maximum Ad value was found to correspond to about 50% 2-propanol. The possible phenomena implied in the absorbance changes are discussed taking into account the peculiar action of 2-propanol on the water structure and content in the bulk phase within the paper capillaries and inside the macromolecular and aggregation structures of RNA and cellulose.

Studies in human embryo fibroblasts infected with measles or herpes simplex virus showed a reduction in virus yield when cultures were pretreated with 1-10 mM lithium chloride doses. Maximum effect was obtained by a 1 h treatment with 10 mM lithium chloride, preceding viral infection by 19-24 hours. A specific antiviral effect against measles virus was manifest immediately after culture pretreatment. Intermittent treatment with 10 mM lithium chloride of cultures persistently infected with measles or herpes virus obtained from human myeloid K-562 cell line shows a reduction in the extracellular virus yield. In the K-562/herpes virus system, the culture treatment with lithium chloride and acyclovir (10 microM) has an additive inhibitory effect on virus production. The paper is focused on the mechanism of lithium chloride antiviral action and the expediency of lithium therapy in SSPE (subacute sclerosing panencephalitis).

A bichromatic ultramicromethod on paper disks was used to determine the age-dependence of capillary blood RNase activity in healthy infants and young children.

The paper reports on serological results obtained by HAI tests against several alphaviruses - eastern equine encephalitis (EEE), western equine encephalitis (WEE), Chikungunya, Midlebourg, Semliki Forest, Sindbis, and Ilheus viruses - carried out in humans and some domestic animals in a region with an intensive circulation of migratory birds. It was possible to detect in human antibodies to EEE, WEE, and Sindbis viruses, but in very low proportions (1.8%, 0.4%, and 0.6%, respectively). Serological results obtained in animals were practically negative: antibodies to EEE virus were found only in one out of 93 horses investigated.

Bichromatic paper disk spectrophotometry allowed the demonstration of an analogy between the increase in the solubility of highly polymerized RNA complexed with streptomycin cations (which accounts for the preservation in vivo of the infectivity of a viral RNA--streptomycin complex) and the effect of a cellulose/solution interface on the distribution of the highly polymerized RNA.

The paper is a review of researches done at the "Stefan S. Nicolau" Institute of Virology, in Bucharest, the last five years, in the antiviral chemotherapy field, as well as of the chemotherapeutical implications of studies conducted about other aspects of virology.

The report is a review of the research and results of the "Stefan S. Nicolau" Institute of Virology scientists in the field of herpes viruses, as they were materialized in the great number of published or communicated scientific papers these last ten years.