Defending the fort: a role for defensin-2 in limiting Rickettsia montanensis infection of Dermacentor variabilis.

The importance of tick defensins is evidenced by their expression in a wide variety of tick tissues and prevalence across many tick genera. To date, the functional and biological significance of defensin-2 as a rickettsiastatic or rickettsiacidal antimicrobial peptide has not been addressed. In a previous study, defensin-2 transcription was shown to increase in Dermacentor variabilis ticks challenged with Rickettsia montanensis. In the present study, the hypothesis that defensin-2 is functional as a rickettsiastatic and/or rickettsiacidal antimicrobial peptide is tested. We show that defensin-2 plays a role in reducing burden after acquisition of Rickettsia montanensis through capillary feeding. Moreover, defensin-2 is shown to associate with R. montanensis in vitro and in vivo, causing cytoplasmic leakiness.

Detecting larval export from marine reserves.

Marine reserve theory suggests that where large, productive populations are protected within no-take marine reserves, fished areas outside reserves will benefit through the spillover of larvae produced in the reserves. However, empirical evidence for larval export has been sparse. Here we use a simple idealized coastline model to estimate the expected magnitude and spatial scale of larval export from no-take marine reserves across a range of reserve sizes and larval dispersal scales. Results suggest that, given the magnitude of increased production typically found in marine reserves, benefits from larval export are nearly always large enough to offset increased mortality outside marine reserves due to displaced fishing effort. However, the proportional increase in recruitment at sites outside reserves is typically small, particularly for species with long-distance (on the order of hundreds of kilometers) larval dispersal distances, making it very difficult to detect in field studies. Enhanced recruitment due to export may be detected by sampling several sites at an appropriate range of distances from reserves or at sites downcurrent of reserves in systems with directional dispersal. A review of existing empirical evidence confirms the model's suggestion that detecting export may be difficult without an exceptionally large differential in production, short-distance larval dispersal relative to reserve size, directional dispersal, or a sampling scheme that encompasses a broad range of distances from the reserves.

Synchronous in situ ATPase activity, mechanics, and Ca2+ sensitivity of human and porcine myocardium.

Flash-frozen myocardium samples provide a valuable means of correlating clinical cardiomyopathies with abnormalities in sarcomeric contractile and biochemical parameters. We examined flash-frozen left-ventricle human cardiomyocyte bundles from healthy donors to determine control parameters for isometric tension (P(o)) development and Ca(2+) sensitivity, while simultaneously measuring actomyosin ATPase activity in situ by a fluorimetric technique. P(o) was 17 kN m(-2) and pCa(50%) was 5.99 (28 degrees C, I = 130 mM). ATPase activity increased linearly with tension to 132 muM s(-1). To determine the influence of flash-freezing, we compared the same parameters in both glycerinated and flash-frozen porcine left-ventricle trabeculae. P(o) in glycerinated porcine myocardium was 25 kN m(-2), and maximum ATPase activity was 183 microM s(-1). In flash-frozen porcine myocardium, P(o) was 16 kN m(-2) and maximum ATPase activity was 207 microM s(-1). pCa(50%) was 5.77 in the glycerinated and 5.83 in the flash-frozen sample. Both passive and active stiffness of flash-frozen porcine myocardium were lower than for glycerinated tissue and similar to the human samples. Although lower stiffness and isometric tension development may indicate flash-freezing impairment of axial force transmission, we cannot exclude variability between samples as the cause. ATPase activity and pCa(50%) were unaffected by flash-freezing. The lower ATPase activity measured in human tissue suggests a slower actomyosin turnover by the contractile proteins.

Time-resolved equatorial X-ray diffraction studies of skinned muscle fibres during stretch and release.

Equatorial X-ray diffraction patterns were recorded from small bundles of one to three chemically skinned frog sartorius muscle fibres (time resolution 250 microseconds) during rapid stretch and subsequent release. In the relaxed state, the dynamic A-band lattice spacing change as a result of a 2 % step stretch (determined from the positions of the 10 and 11 reflections) resulted in a 21 % increase in lattice volume, while static studies of spacing and sarcomere length indicated than an increase in volume of >/=50 % for the same length change. In rigor, stretch caused a lattice volume decrease which was reversed by a subsequent release. In activated fibres (pCa 4.5) exposed to 10 mM 2,3-butanedione 2-monoxime (BDM), stretch was accompanied by a lattice compression exceeding that of constant volume behaviour, but during tension recovery, compression was partially reversed to leave a net spacing change close to that observed in the relaxed fibre. In the relaxed state, spacing changes were correlated with the amplitude of the length step, while in rigor and BDM states, spacing changes correlated more closely with axial force. This behaviour is explicable in terms of two components of radial force, one due to structural constraints as seen in the relaxed state, and an additional component arising from cross-bridge formation. The ratio of axial to radial force for a single thick filament resulting from a length step was four in rigor and BDM, but close to unity for the relaxed state.

Quantitative assessment of cell damage in situ: electron microprobe X-ray analysis of model organisms treated with noxious species.

The existing set of methods for assessing toxicity of noxas, based on experiments with whole animals (subclinical toxicity, toxicokinetics, carcinogenity, teratogenity, neurotoxicology etc.) does not provide much information about cellular and subcellular effects such compounds may exert. We suggest to complement the current methodology by combining a traditional morphological observation in an electron microscope with a spectroscopic method of electron microprobe X-ray analysis (or X-ray microanalysis). The latter makes it possible to measure concentrations of chemical elements in individual cells and organelles and effects of noxas can thus be assessed (i) at subcellular level, (ii) directly in situ and (iii) quantitatively. Concentrations of biologically important elements such as phosphorus, sulfur or zinc were measured in individual organelles in both intact and noxa-treated tissues, thus offering a possibility of comparing the effects of various noxious species at subcellular level (with the noxa previously applied to whole tissue or animal). The suggested correlation of analytical and morphological information may also provide new insights into cellular targeting of noxas (and potentially also drugs) as some organelles appear to be much more susceptible to damage than others.

Capillary force-driven cell perfusion microchamber: calcium transients in isolated smooth muscle cells.

We present a new design for a sub-microlitre chamber which enables perfusion of individual cells. No equipment is required for it to be operational, as the exchange of solutions in the chamber is driven solely by capillary forces. Its active volume consists of a 30-micron-thin layer between two coverslips (separated by a couple of spacers) and is adjustable down to 0.1 microl. This slimline design (1) guarantees that all cells are kept in one (focal) plane during recording/perfusion (thus minimizing movement artefacts when intracellular fluorescence is monitored); (2) facilitates fixing of cells to a coverslip (often even without the use of poly-L-lysine, especially when small cell clusters are used); and (3) makes it possible to perfuse individual cells on a specimen stage of an upright microscope even under high-power objectives with a short working distance, which is of potential use in field studies where the smaller size of an upright microscope (compared to the inverted one) can be advantageous. As an example, we present a chamber with an active volume of approx. 0.5 microl and perfusion rate high enough to enable complete exchange of solution within 250 ms in an area of 500 micron x 500 micron. Only 1 microl of perfusing solution is required for exchanging the entire volume of the chamber. We present an example of intracellular free calcium transients in isolated smooth muscle cells upon release of intracellular sequestered calcium.

[Dermoid cysts of the oral cavity]. / Torbiele skórzaste dna jamy ustnej.

The authors describe ethiology, clinical picture, diagnosis and treatment of the dermoid cyst of oral cavity floor. They show the advantages after using ultrasonography and computer tomography in treatment of these cysts.

[Use of computerized tomography for localization of a foreign body impacted into the cranium]. / Wykorzystanie tomografii komputerowej do lokalizacji ciala obcego wtloczonego w obreb twarzoczaski.

A case is presented of impaction of a metal bar into the cranium i an 8-year-old child. The significant importance for the therapeutic management was radiological examination, especially CT of the head. It made easier the determination of the foreign body locality in relation to the anterior cranial fossa and could allow to do the assessment of the resolution of air accumulation in the frontal lobe.

Electron microprobe study of the effect of long-term vacuum storage of freeze-dried cryosections on distribution of elements in cells.

The distribution of elements in yeast cells was measured on freshly prepared, freeze-dried cryosections and compared with the distribution obtained on the same sections after storage for 20 months in a vacuum below 2.6 kPa. The average concentration of phosphorus remained unchanged but was equalized throughout the cells, i.e. it migrated from vacuoles into the cytoplasm and mitochondria. Zinc remained preferentially localized in the vacuoles, but the ratio between vacuolar and cytoplasmic zinc concentrations decreased about three-fold. Cytoplasmic and mitochondrial concentrations of potassium remained unchanged while partial release from the vacuoles and subsequently from the cells was observed. This resulted in a homogeneous distribution of potassium in the cells after 20 months and some of the vacuolar potassium appeared in spectra of formvar film measured several micrometres from the cells. A large increase in the sodium (from 160 to 360% more than in fresh sections), magnesium (from 110 to 200% more) and sulphur (from 70 to 350% more) contents was observed in all cellular compartments (except for vacuoles, where only a 20% increase in the magnesium content was observed), while chlorine was almost completely released from the cells. The limitations of the use of long-term vacuum-stored cryosections for electron microprobe analysis of cells are discussed.