The First Strand Transfer during HIV-1 Reverse Transcription Can Occur either Intramolecularly or Intermolecularly

AbstractReverse transcription is a complicated process that involves at least two cDNA transfer reactions to produce a full-length copy DNA of the retroviral RNA genome. Because one retrovirus particle contains two identical genomic RNA molecules, the transfers can occur in an intramolecular or intermolecular manner. The mechanism of the first transfer step (minus-strand strong-stop cDNA transfer) has been studied previously in detail in transduction experiments with spleen necrosis virus vectors containing genetic markers. Different results have been reported with respect to the type of strand transfer mechanism. In this study, we analyzed the first strand transfer for human immunodeficiency virus type 1 (HIV-1). Two genetically marked genomes were copackaged into virions and reverse transcription was initiated within these particles upon permeabilization by NP-40 and addition of dNTPs. To test whether intrastrand or interstrand transfer had occurred, the cDNA products of this endogenous reverse transcription reaction were extracted from the virions and analyzed for the presence of restriction enzyme recognition sites provided by the genetic markers. The results of this analysis demonstrated that the first DNA transfer reaction occurs in a random manner, with approximately the same contribution of intrastrand and interstrand transfers. The ability to perform intermolecular strand transfer was lost upon extraction of the dimeric RNA template from the virion particle

Basic theorems for parallel processes in timed mu mu CRL

Timed $mucrl$ is a process algebra-based formalism for the specification and verification of parallel, communicating systems with explicit time cite{Gr97. In this paper various basic results are derived, such as theorems for {it basic forms/, the expansion of terms with operators for parallelism, elimination of parallelism, and commutativity and associativity of the merge and communication merge (the operators $|$ and $|$). The interpretation of the operators, in particular the left merge, is far from trivial, and more in general, it has to be stated that working with a time-based formalism such as timed $mucrl$ can be fairly complicated. Therefore we pay a lot of attention to all kinds of proof details that could enhance the understanding -- and thus facilitate the use -- of the formalism. Many basic lemmas are included, and examples are used to illustrate the intuition behind the various results

Completeness of timed µCRL

In [9], a straightforward extension of the process algebra µCRL was proposed to explicitly deal with time. The process algebra µCRL has been designed especially to deal with data in a process algebraic context. Using the features for data, only a minor extension of the language was needed to obtain a very expressive variant of time. But [9] contains syntax, operational semantics and axioms characterising timed µCRL. It did not contain an in-depth analysis of timed µCRL. This paper fills this gap by providing soundness and completeness results. The main tool to establish these is a mapping of timed to untimed µCRL and employing the completeness results obtained for untimed µCRL

Remote manipulation of cells with ultrasound and microbubbles

Ultrasound in combination with contrast microbubbles has been shown to alter the permeability of cell membranes. This permeabilization feature is used to design new drug delivery systems using ultrasound and contrast agents. Although the exact underlying mechanisms are still unknown, one hypothesis is that oscillating microbubbles cause cell deformation resulting in enhanced cell membrane permeability. In this paper we show the actions of oscillating microbubbles on cultured cells under a microscope recorded with a fast framing camera at 10 million frames per second. Optical observations of microbubbles and cultured cells is possible through the use of a microscope mounted in front of the fast framing camera Brandaris128. The Brandaris128 is capable of recording a sequence of 128 images with a frame rate up to 25 million frames per second. Pig aorta endothelial cells were grown on the inside of an Opticell/spl trade/ container. A diluted suspension of experimental agents BR14 (Bracco Research, Geneva, Switzerland) was added. Ultrasound exposure consisted of one burst of 6 cycles at a frequency of 1 MHz and a P/spl I.bar/ of 0.5 MPa. During ultrasound transmission, the interactions between BR14 microbubbles and cultured cells were recorded using a frame rate of 10 million frames per second. Cell deformation as a result of vibrating microbubbles is studied. Cell deformation is quantified through measuring the displacement of the cells. Microbubble vibration is quantified by measuring its initial, maximal, and minimal radii. We observed that upon ultrasound arrival and microbubble oscillations, the cell membrane deforms up to a few micrometers in length as a result of the oscillation of the microbubble. The membrane deformation rate changes with the oscillation strength of the microbubble. During the sonication, changes in the cross-sectional distance of the cultured cells were observed due to microbubble vibrations. Depending on the maximal vibrations of the microbubble and the distance between the microbubble and the cell, the displacement of the cells varied form 0 to 20% of the cell size. This study reveals the action of oscillating microbubbles on cells. It is known that living cells sense mechanical forces thus there is no doubt that perturbation of the oscillating microbubbles results in profound alterations in the cellular content. This study is the beginning of revealing the functional relationships that lie beyond the remote manipulation of cells and ultrasound microbubble induced permeabilization of the cell membrane

Serological profiles in nursery piglets colonized with Staphylococcus aureus

At present, the immune response of pigs in relation to Staphylococcus aureus carriage is poorly understood. This study aimed at investigating the dynamics of the anti-staphylococcal humoral immune response in methicillin-susceptible S. aureus (MSSA)-positive piglets and at assessing the effect of the experimental introduction of a methicillin-resistant S. aureus (MRSA) Sequence Type (ST) 398 strain. Therefore, serum samples were collected at different times from 31 weaned piglets originating from four different sows. Twenty-four out of the 31 piglets were challenged with MRSA ST398. The serum samples were analysed for IgG antibodies to 39 S. aureus antigens, using a multiplex bead-based assay (xMAP technology, Luminex Corporation). Though antibody responses showed broad inter-individual variability, serological results appeared to be clustered by litter of origin. For most antigens, an age-related response was observed with an apparent increase in antibody titres directed against staphylococcal microbial surface components recognizing adhesive matrix molecules (MSCRAMMs), which have been shown to play a role in S. aureus colonization. In most animals, antibody titres directed against staphylococcal toxins or immune-modulating proteins decreased with age, possibly reflecting absence of bacterial invasion. The introduction of MRSA ST398 did not elicit a significant humoral immune reaction. This study describes, for the first time, the humoral immune response in weaned pigs colonized with S. aureus

Europees recht

The progression of EU law: Accommodating change and upholding value

Completeness of timed mu mu CRL

We provide soundness and completeness results for the extension of muCRL with time put forward by Groote. The specification language muCRL has been designed especially to deal with data in a process algebraic context. Using the features for data, only a minor extension of the language was needed to obtain a very expressive variant of time. The main tool to establish the completeness result is a mapping of timed to untimed muCRL and employing the completeness results obtained for untimed muCRL