Comparative study of the coupling between topoisomerase I activity and high-mobility group proteins in E. coli and mammalian cells

It is now well established that the HMG box DNA-binding motif can alter the topology of double-stranded DNA in several ways. Using the spermatid-specific tsHMG as a model protein of the HMG-1/-2 family, we have demonstrated that its expression in E. coli produces an increase in plasmid supercoiling density that is likely a consequence of its ability to constrain free supercoils in vivo. As demonstrated in vitro, stabilization of free DNA supercoils by tsHMG prevents topoisomerase I from gaining access to the template and could represent a mechanism for the apparent inhibition of topoisomerase I in bacteria. A similar modulation of eukaryotic topoisomerase I activity was not detected after expression of the tsHMG in mammalian cells. This differential response is discussed in terms of the marked difference in DNA packaging and accessibility of free supercoils in prokaryotic vs. eukaryotic cells.     

Transposon tagging in diploid strawberry

Fragaria vesca was transformed with a transposon tagging construct harbouring amino terminally deleted maize transposase and EGFP (Ac element), NPTII, CaMV 35S promoter (P35S) driving transposase and mannopine synthase promoter (Pmas) driving EGFP (Ds element). Of 180 primary transgenics, 48 were potential launch pads, 72 were multiple insertions or chimaeras, and 60 exhibited somatic transposition. T(1) progeny of 32 putative launch pads were screened by multiplex PCR for transposition. Evidence of germ-line transposition occurred in 13 putative launch pads; however, the transposition frequency was too low in three for efficient recovery of transposants. The transposition frequency in the remaining launch pads ranged from 16% to 40%. After self-pollination of the T(0) launch pads, putative transposants in the T(1) generation were identified by multiplex PCR. Sequencing of hiTAIL-PCR products derived from nested primers within the Ds end sequences (either P35S at the left border or the inverted repeat at the right border) of T(1) plants revealed transposition of the Ds element to distant sites in the strawberry genome. From more than 2400 T(1) plants screened, 103 unique transposants have been identified, among which 17 were somatic transpositions observed in the T(0) generation. Ds insertion sites were dispersed among various gene elements [exons (15%), introns (23%), promoters (30%), 3' UTRs (17%) as well as intergenically (15%)]. Three-primer (one on either side of the Ds insertion and one within the Ds T-DNA) PCR could be used to identify homozygous T(2) transposon-tagged plants. The mutant collection has been catalogued in an on-line database.     

Analysing gait using a force-measuring walkway: intrasession repeatability in healthy children and adolescents

The goal of this study was to determine the repeatability of gait parameters measured by a force plate gait analysis system (Leonardo Mechanograph^® GW) in healthy children. Nineteen healthy children and adolescents (age range: 7–17 years) walked at a self-selected speed on an 11-m-long walkway. Vertical ground reaction forces were measured in the central 6 m of the walkway. Each participant performed three blocks of three trials while walking barefoot and three blocks of three trials while wearing shoes. There were no differences between trials within each condition. All force and spatiotemporal parameters had intraclass correlation coefficients above 0.87 and coefficients of variation in the order of 1–6%. In this group of healthy children and adolescents, gait analysis with a force plate system produced repeatable intra-day results.     

Solid-phase synthesis and some biological properties of ovine corticotropin-releasing factor

Ovine corticotropin-releasing factor (CRF) was synthesized by solid-phase method and isolated using two purification steps: gel filtration and high performance liquid chromatography. The synthetic peptide is a potent stimulator of ACTH release, as well as cyclic AMP accumulation and release in rat adenohypophyseal cells in culture and shows highly specific binding to bovine anterior pituitary plasma membranes.     

Time-gated interferometric detection increases Raman scattering to fluorescence signal ratio in biological samples

Attainable levels of signal-to-background ratio (SBR) in Raman spectroscopy of biological samples is limited by the presence of endogenous fluorophores. It is customary to remove the ubiquitous fluorescence background using postacquisition data processing. However, new approaches are needed to reduce background contributions and maximize the fraction of the sensor dynamical range occupied by Raman photons. Time-resolved detection using pulsed lasers and time-gated measurements can be used to address the signal-to-background problem in biological samples by limiting light detection to nonresonant interaction phenomena with relaxation time scales occurring on sub-nanosecond time scales, thereby excluding contributions from resonant phenomena such as fluorescence. A time-gated Fourier-transform spectrometer was assembled using a commercially available interferometer, a single channel single-photon avalanche diode and time tagging electronics. A time gate of 300 ps increased the signal-to-background-ratio of the 1440 cm^?1 Raman band from 36% to 69% in an olive oil sample hereby demonstrating the potential of this approach for autofluorescence suppression.      

L'utilisation de services de santé et de médicaments par des personnes agées de Montréal qui re?oivent des soins maintien à domicile.

A survey was conducted among 160 persons aged 64 year or more in Montreal who were receiving home care. They answered at home a questionnaire on their use of health care services and drugs, and showed the interviewer all the drugs they were taking. In comparison with similar data from elsewhere, the use of health care services (an average of 8.0 encounters with a physician per person per year) and of drugs (an average of 5.3 per person) by this group seems high. Perhaps this group of people was obviously sicker than others of the same age, but this remains to be shown. Moreover, despite the reported frequency of health problems, it is uncertain whether such use of services and drugs was necessary. The question is raised whether the home care system is doing for the patient what it was intended to do.