Unexpected silicon localization in calcium carbonate exoskeleton of cultured and fossil coccolithophores.

Coccolithophores, marine calcifying phytoplankton, are important primary producers impacting the global carbon cycle at different timescales. Their biomineral structures, the calcite containing coccoliths, are among the most elaborate hard parts of any organism. Understanding the morphogenesis of coccoliths is not only relevant in the context of coccolithophore eco-physiology but will also inform biomineralization and crystal design research more generally. The recent discovery of a silicon (Si) requirement for crystal shaping in some coccolithophores has opened up a new avenue of biomineralization research. In order to develop a mechanistic understanding of the role of Si, the presence and localization of this chemical element in coccoliths needs to be known. Here, we document for the first time the uneven Si distribution in Helicosphaera carteri coccoliths through three synchrotron-based techniques employing X-ray Fluorescence and Infrared Spectromicroscopy. The enrichment of Si in specific areas of the coccoliths point to a targeted role of this element in the coccolith formation. Our findings mark a key step in biomineralization research because it opens the door for a detailed mechanistic understanding of the role Si plays in shaping coccolith crystals.

Interface induced diffusion.

Interface induced diffusion had been identified in a thin film system damaged by electron bombardment. This new phenomenon was observed in Al2O3 (some nm thick)/Si substrate system, which was subjected to low energy (5 keV) electron bombardment producing defects in the Al2O3 layer. The defects produced partially relaxed. The rate of relaxation is, however, was different in the vicinity of the interface and in the "bulk" parts of the Al2O3 layer. This difference creates an oxygen concentration gradient and consequently oxygen diffusion, resulting in an altered layer which grows from the Al2O3/Si substrate interface. The relative rate of the diffusion and relaxation is strongly temperature dependent, resulting in various altered layer compositions, SiO2 (at room temperature), Al2O3 + AlOx + Si (at 500 °C), Al2O3 + Si (at 700 °C), as the temperature during irradiation varies. Utilizing this finding it is possible to produce area selective interface patterning.

Coccolith crystals: Pure calcite or organic-mineral composite structures?

The localization of organic material within biominerals is central to developing biomineral formation mechanisms. Coccoliths, morphologically sophisticated calcite platelets of intracellularly calcifying coccolithophores, are not only eco-physiologically important, but also influence biogeochemical cycles through mass production. Despite their importance and over a century of research, the formation mechanism of coccoliths is still poorly understood. Crucial unsolved questions include the localization of organic material within coccoliths. In extracellular calcifiers the discovery of an organics-containing nano-structure within seemingly single crystals has led to the formulation of a two-step crystallization mechanism. Coccoliths are traditionally thought of as being formed by a different mechanism, but it is unclear whether coccolith crystals possess a nano-structure. Here we review the evidence for and against such a nano-structure. Current SXPD analyses suggest a nano-structure of some kind, while imaging methods (SEM, TEM, AFM) provide evidence against it. We suggest directions for future research which should help solve this puzzle. STATEMENT OF SIGNIFICANCE: Coccolithophores, unicellular calcifying algae, are important primary producers and contribute significantly to pelagic calcium carbonate export. Their calcite platelets, the coccoliths, are amongst the most sophisticated biomineral structures. Understanding the crystallization mechanism of coccolith crystals is not only central to coccolithophore cell biology but also lies at the heart of biomineralization research more generally. The crystallization mechanism of coccoliths has remained largely elusive, not least because it is still an open question whether the micron sized coccolith crystals are pure calcite, or contain organic material. Here we review the state of the art and suggest a way to solve this central problem.

Electron irradiation induced amorphous SiO2 formation at metal oxide/Si interface at room temperature; electron beam writing on interfaces.

Al2O3 (5 nm)/Si (bulk) sample was subjected to irradiation of 5 keV electrons at room temperature, in a vacuum chamber (pressure 1 × 10-9 mbar) and formation of amorphous SiO2 around the interface was observed. The oxygen for the silicon dioxide growth was provided by the electron bombardment induced bond breaking in Al2O3 and the subsequent production of neutral and/or charged oxygen. The amorphous SiO2 rich layer has grown into the Al2O3 layer showing that oxygen as well as silicon transport occurred during irradiation at room temperature. We propose that both transports are mediated by local electric field and charged and/or uncharged defects created by the electron irradiation. The direct modification of metal oxide/silicon interface by electron-beam irradiation is a promising method of accomplishing direct write electron-beam lithography at buried interfaces.

Coccospheres confer mechanical protection: New evidence for an old hypothesis.

UNLABELLED: Emiliania huxleyi has evolved an extremely intricate coccosphere architecture. The coccosphere is comprised of interlocking coccoliths embedded in a polysaccharide matrix. In this work, we performed in-situ scanning electron microscopy based compression tests and conclude that coccospheres have a mechanical protection function. The coccosphere exhibits exceptional damage tolerance in terms of inelastic deformation, recovery and stable crack growth before catastrophic fracture, a feature, which is not found in monolithic ceramic structures. Some of the mechanical features of the coccospheres are due to their architecture, especially polysaccharide matrix that acts as a kind of bio-adhesive. Our data provide strong evidence for the mechanical protection-hypothesis of coccolithophore calcification, without excluding other functions of calcification such as various biochemical roles discussed in the literature. STATEMENT OF SIGNIFICANCE: Although bio-mechanics of shell structures like nacre have been studied over the past decade, coccospheres present an architecture that is quite distinct and complex. It is a porous cell structure evolved to protect the living algae cell inside it in the oceans, subjected to significant hydrostatic pressure. Despite being made of extremely brittle constituents like calcium carbonate, our study finds that coccospheres possess significant damage tolerance especially due to their interlocking coccolith architecture. This will have consequences in bio-mimetic design, especially relating to high pressure applications.

Types of indwelling urinary catheters for long-term bladder drainage in adults.

BACKGROUND: Prolonged urinary catheterisation is common amongst people in long-term care settings and this carries a high risk of developing a catheter-related urinary tract infection and associated complications. A variety of different kinds of urethral catheters are available. Some have been developed specifically to lower the risk of catheter-associated infection, for example antiseptic or antibiotic impregnated catheters. Ease of use, comfort and handling for the caregivers and patients, and cost-effectiveness are also important factors influencing choice. OBJECTIVES: The primary objective was to determine which type of in-dwelling urinary catheter is best to use for long-term bladder drainage in adults. SEARCH STRATEGY: We searched the Cochrane Incontinence Group Specialised Trials Register (searched 15 December 2004), MEDLINE (January 1950 to February 2005) and CINAHL (January 1982 to February 2005). We also handsearched 28 relevant journals and conference proceedings. We examined the bibliographies of relevant articles and contacted catheter manufacturers, scientific societies and experts for trials. SELECTION CRITERIA: All randomised trials comparing types of indwelling urinary catheters for long-term catheterisation in adults. Long-term catheterisation was defined as more than 30 days. DATA COLLECTION AND ANALYSIS: Data extraction has been undertaken by two review authors independently and simultaneously. Any disagreement has been resolved by a third review author. The included trial data were handled according to the description of the Cochrane Collaboration Reviewers' Handbook. MAIN RESULTS: Three trials were included involving 102 adults in various settings. Two trials had a parallel group design and one was a randomised cross-over trial. Only two of the six targeted comparisons were assessed by these trials: antiseptic impregnated catheters versus standard catheters (one trial) and one type of standard catheter versus another standard catheter (two trials). The single small cross-over trial was inadequate to assess the value of silver alloy (antiseptic) impregnated catheters. In the two trials comparing different types of standard catheters, estimates of differences were all imprecise because the trials also had small sample sizes: confidence intervals were too wide to rule out clinically important differences. One trial did suggest, however, that the use of a hydrogel coated latex catheter rather than a silicone catheter may be better tolerated (RR for need for early removal 0.41, 95% CI 0.22 to 0.77). AUTHORS' CONCLUSIONS: Very few trials have compared types of catheter for long-term bladder drainage. All were small and showed methodically weaknesses. Therefore, the evidence was not sufficient as a reliable basis for practical conclusions. Further, better quality trials are needed to address the current lack of evidence in this clinically important area.

Evaluation of the dissemination and implementation of a nutritional guideline for pressure ulcer care.

OBJECTIVE: In 2004 the European Pressure Ulcer Advisory Panel nutritional working group developed a nutritional guideline for pressure ulcer prevention and treatment. This study investigated the degree to which the guideline was disseminated and implemented in clinical practice. METHOD: A cross-sectional study was undertaken in health-care organisations in The Netherlands, Germany and the UK. A printed, standardised questionnaire which followed Rogers' model of the innovation-decision process was developed, translated and distributed to 1087 health-care organisations. RESULTS: The response rate was 33% (n = 363). Sixty-one per cent of respondents knew of the guideline. Twenty-five per cent had applied it to their clinical practice and used it for nutritional screening. The main barrier to the provision of nutritional support appeared to be lack of knowledge and skills. CONCLUSION: One year after its dissemination, more than half of respondents knew of the guideline, with one in four applying it to their practice. The guideline was better disseminated and implemented in The Netherlands and UK than in Germany, where only 4% of participants had used it.

Self-cooling of a micromirror by radiation pressure.

Cooling of mechanical resonators is currently a popular topic in many fields of physics including ultra-high precision measurements, detection of gravitational waves and the study of the transition between classical and quantum behaviour of a mechanical system. Here we report the observation of self-cooling of a micromirror by radiation pressure inside a high-finesse optical cavity. In essence, changes in intensity in a detuned cavity, as caused by the thermal vibration of the mirror, provide the mechanism for entropy flow from the mirror's oscillatory motion to the low-entropy cavity field. The crucial coupling between radiation and mechanical motion was made possible by producing free-standing micromirrors of low mass (m approximately 400 ng), high reflectance (more than 99.6%) and high mechanical quality (Q approximately 10,000). We observe cooling of the mechanical oscillator by a factor of more than 30; that is, from room temperature to below 10 K. In addition to purely photothermal effects we identify radiation pressure as a relevant mechanism responsible for the cooling. In contrast with earlier experiments, our technique does not need any active feedback. We expect that improvements of our method will permit cooling ratios beyond 1,000 and will thus possibly enable cooling all the way down to the quantum mechanical ground state of the micromirror.

SPINE workshop on automated X-ray analysis: a progress report.

The Structural Proteomics In Europe (SPINE) consortium contained a workpackage to address the automated X-ray analysis of macromolecules. The aim of this workpackage was to increase the throughput of three-dimensional structures while maintaining the high quality of conventional analyses. SPINE was able to bring together developers of software with users from the partner laboratories. Here, the results of a workshop organized by the consortium to evaluate software developed in the member laboratories against a set of bacterial targets are described. The major emphasis was on molecular-replacement suites, where automation was most advanced. Data processing and analysis, use of experimental phases and model construction were also addressed, albeit at a lower level.

Modeling parameter dependence from time series.

Two approaches for modeling of parameter dependence of dynamical systems from time series are investigated and applied to different examples. For both methods it is assumed that a few time series are available that have been measured for different (known) parameter values of the underlying (experimental) dynamical system. The objective is to model the changing dynamics of the system as a function of its parameters and to use this for experimental bifurcation analysis. Using parametrized families the tasks of modeling the dynamics and of modeling its parameter dependence are separated. Technical difficulties that may occur with this approach are discussed and illustrated. An alternative are extended state space models where both modeling tasks are treated simultaneously. To obtain reliable models from a few time series only, ensembles of models are employed that show very good extrapolation and generalization properties.

Modelling bound ligands in protein crystal structures.

Methods for automated identification and building of protein-bound ligands in electron-density maps are described. An error model of the geometrical features of the molecular structure of a ligand based on a lattice distribution of positional parameters is obtained via simulation and is used for the construction of an approximate likelihood scoring function. This scoring function combined with a graph-based search technique provides a flexible model-building scheme and its application shows promising initial results. Several ligands with sizes ranging from 9 to 44 non-H atoms have been identified in various X-ray structures and built in an automatic way using a minimal amount of prior stereochemical knowledge.

Spectral encoding of the polarization state of light in multiplexed polarization-sensitive lasing structures.

We report the experimental demonstration of spectral encoding of the polarization state of light by use of multiplexed distributed-feedback lasers in a dye-doped organic thin film by exploiting the pump polarization selectivity of the superimposed resonators. Measurement of the Stokes parameters of the pump light without a priori knowledge of the lasing properties of the structure is discussed.

All-optical tunability of holographically multiplexed organic distributed feedback lasers.

We report the fabrication and characterization of optically pumped multiple grating distributed feedback lasers in dye doped organic thin films. Each multiplexed laser structure is inscribed at a different angle in the sample plane and possesses a unique emission wavelength. The polarization sensitivity of these structures with respect to the pumping light is exploited to enable simple and high-speed switching of the device emission wavelength.

Nutritional interventions for preventing and treating pressure ulcers.

BACKGROUND: Pressure ulcers affect 10% of people in hospitals and older people are at highest risk. The correlation between nutritional intake and the development of pressure ulcers is suggested by several studies, but the results are inconsistent. OBJECTIVES: To evaluate the effectiveness of enteral and parenteral nutrition on the prevention and treatment of pressure ulcers. SEARCH STRATEGY: The Cochrane Wounds Group Specialised Trials Register and the Cochrane Central register of Controlled Trials were searched in September 2002. An additional search of PubMed and Cinahl and hand search of conference proceedings and journals was performed, bibliographies of relevant articles were examined and experts in the field as well as manufacturers were contacted in order to find additional literature that may be relevant. SELECTION CRITERIA: Randomised controlled trials evaluating the effectiveness of enteral or parenteral nutrition on the prevention and treatment of pressure ulcers by measuring the incidence of new ulcers, ulcer healing or changes in pressure ulcer severity. There were no restrictions on patients, setting, date, publication status or language. DATA COLLECTION AND ANALYSIS: Abstracts were independently inspected and full articles were obtained of potentially relevant studies. In case of disagreement advice was sought from a third person (AK). Data extraction and assessment of quality were undertaken by the three reviewers independently. MAIN RESULTS: Only 8 randomised controlled trials out of 16 potentially relevant articles were included. However, most of the 8 trials included are small and of poor methodological quality. PREVENTION: Four studies compared a combination of nutritional supplements, consisting of a minimum of energy and protein in different dosages, for the prevention of pressure ulcers. The largest study found that nutritional supplements reduced the number of new pressure ulcers (Bourdel-M 2000). The three smaller studies lacked power. TREATMENT: Four studies evaluated the effects of nutritional supplements for the treatment of existing pressure ulcers: one trial examined mixed nutritional supplements, one trial examined zinc, another the effect of proteins, and two studies compared ascorbic acid. The trials included are heterogeneous with regard to participants, interventions and outcomes; therefore it was considered inappropriate to perform a meta-analysis. REVIEWER'S CONCLUSIONS: It was not possible to draw any firm conclusions on the effect of enteral and parenteral nutrition on the prevention and treatment of pressure ulcers. Further trials of high methodological quality are necessary.

[TFF peptides. New mucus-associated secretory products of the conjunctiva]. / TFF-Peptide. Neue mukusassoziierte Sekretionsprodukte der Konjunktiva.

The molecular architecture of the human ocular mucus is not yet completely understood. Recently, TFF peptides (formerly known as trefoil factors or P-domain peptides) could be identified as new constituents of this delicate mucus. Members of the TFF-peptide family are typical secretory products of mucous epithelia and three are known in humans and designated as TFF1, TFF2 and TFF3. They enhance cell migratory processes (motogenic effect), they show anti-apoptotic effects and are inflammatory modulators Both TFF1 and TFF3 expression could be monitored by the reverse transcription-polymerase chain reaction (RT-PCR) in the human conjunctiva; in contrast, TFF2 transcripts were not detectable. Using immunohistochemistry, TFF1 and TFF3 peptides were found in varying concentrations solely in secretory vesicles of conjunctival goblet cells. This localisation matches precisely that of the secretory mucin MUC5AC. Thus, conjunctival TFF1 and TFF3 have to be considered as typical mucin-associated peptides probably modulating the rheological properties of the ocular mucus and the tear fluid. Future investigations are in progress to elucidate the role of TFF-peptides during pathological conditions of the eye as well as their diagnostic and therapeutic potential.

Synthesis and biological activities of a new series of secosteroids: vitamin D phosphonate hybrids.

By a structural combination of phosphonate and bisphosphonate moieties with the vitamin D skeleton a series of new vitamin D analogs was synthesized. Derivatives with 24beta-hydroxy- or 24-keto groups exerted considerable vitamin D activities in vitro while the hypercalcemic potentials were significantly reduced as compared to 1alpha,25-dihydroxyvitamin D(3) (calcitriol). Whereas the 24-hydroxy analogs did not influence bone formation in vivo in dosages below the hypercalcemic threshold, the 24-ketones were found to induce synthesis of new bone matrix in non-hypercalcemic doses. Vitamin D bisphosphonate hybrids, on the other hand, which did not elicit substantial vitamin D activities in vitro and tend to decrease serum calcium levels in vivo clearly induced osteoid formation in rats, indicating a mechanism of action different to calcitriol.

Hsp70-RAP46 interaction in downregulation of DNA binding by glucocorticoid receptor.

Receptor-associating protein 46 (RAP46) is a cochaperone that regulates the transactivation function of several steroid receptors. It is transported into the nucleus by a liganded glucocorticoid receptor where it downregulates DNA binding and transactivation by this receptor. The N- and C-termini of RAP46 are both implicated in its negative regulatory function. In metabolic labelling experiments, we have shown that the N-terminus of RAP46 is modified by phosphorylation, but this does not contribute to the downregulation of glucocorticoid receptor activity. However, deletion of a sequence that binds 70 kDa heat shock protein (Hsp70) and the constitutive isoform of Hsp70 (Hsc70) at the C-terminus of RAP46 abrogated its negative regulatory action. Surface plasmon resonance studies showed that RAP46 binds the glucocorticoid receptor only when it has interacted with Hsp70/Hsc70, and confocal immunofluorescence analyses revealed a nuclear transport of Hsp70/Hsc70 by the liganded receptor. Together these findings demonstrate an important contribution of Hsp70/Hsc70 in the binding of RAP46 to the glucocorticoid receptor and suggest a role for this molecular chaperone in the RAP46-mediated downregulation of glucocorticoid receptor activity.

Bone condensing in the placement of endosteal palatal implants: a case report.

Bone condensing as a technique to prepare an implant site is demonstrated on a patient who was to undergo orthodontic treatment utilizing a palatal implant as an anchor. Based on the anatomic constraints of the palate and the desire to load the implant as axially as possible, adapted-instrumentation for bone condensing is presented. Bone condensing for preparation of the implant site in soft maxillary bone avoids the risk of heat generation, and palatal implants can be placed precisely with primary stability.

Energetics of Na(+)-Ca(2+) exchange in resting cardiac muscle.

The energetic effect of extracellular Na(+) removal and readmission (in a nominally Ca(2+)-free perfusate) in Langendorff-perfused ventricles of transgenic mice (TM), which overexpress the sarcolemmal Na(+)-Ca(2+) exchanger; normal mice (NM); young (7-12 days old) rats (YR); and older (13-20 days old) rats (OR) was studied. In all heart muscles, extracellular Na(+) removal induced an increase in heat production (H(1)). Na(+) readmission further increased heat production to a peak value (H(2)) followed by a decrease toward initial values. These effects were more marked in the YR and TM as compared with the OR and NM groups, respectively. Caffeine (1 mM), ryanodine (0.2 microM), and verapamil (1 microM) decreased H(1) and H(2) in both rat groups. EGTA (1 mM) decreased H(1) and H(2) in the YR but not in the OR group. Thapsigargin (1 microM) decreased H(1) and H(2) in all four hearts preparations. A possible interpretation is that Na(+)-Ca(2+) exchange acts as an energy-saving mechanism to prevent Ca(2+) accumulation at the junctional sarcoplasmic reticulum zone (JSR) and thus prevents further release of Ca(2+). Extracellular Na(+) removal lead to Ca(2+) accumulation in the JSR inducing further SR-Ca(2+) release and increased energy release. Na(+) readmission removes the accumulated Ca(2+) at the JSR (cleft) zone by exchanging Ca(2+) with Na(+) producing a transitory increase in energy release due to Na(+)-K pump activation.