U12 type introns were lost at multiple occasions during evolution

<p>Abstract</p> <p>Background</p> <p>Two categories of introns are known, a common U2 type and a rare U12 type. These two types of introns are removed by distinct spliceosomes. The phylogenetic distribution of spliceosomal RNAs that are characteristic of the U12 spliceosome, i.e. the U11, U12, U4atac and U6atac RNAs, suggest that U12 spliceosomes were lost in many phylogenetic groups. We have now examined the distribution of U2 and U12 introns in many of these groups.</p> <p>Results</p> <p>U2 and U12 introns were predicted by making use of available EST and genomic sequences. The results show that in species or branches where U12 spliceosomal components are missing, also U12 type of introns are lacking. Examples are the choanoflagellate <it>Monosiga brevicollis</it>, <it>Entamoeba histolytica</it>, green algae, diatoms, and the fungal lineage Basidiomycota. Furthermore, whereas U12 splicing does not occur in <it>Caenorhabditis elegans</it>, U12 introns as well as U12 snRNAs are present in <it>Trichinella spiralis</it>, which is deeply branching in the nematode tree. A comparison of homologous genes in <it>T. spiralis </it>and <it>C. elegans </it>revealed different mechanisms whereby U12 introns were lost.</p> <p>Conclusions</p> <p>The phylogenetic distribution of U12 introns and spliceosomal RNAs give further support to an early origin of U12 dependent splicing. In addition, this distribution identifies a large number of instances during eukaryotic evolution where such splicing was lost.</p

Experimental Investigations on Wear in Oscillating Grease-Lubricated Rolling Element Bearings of Different Size and Type

Grease-lubricated rolling element bearings can suffer from wear due to lubricant starvation under certain oscillating operating conditions. Especially for large-scale slewing bearings, such as blade bearings in wind turbines, experimental investigations are complex compared to small-scale reference testing. For an easier manner of testing, it is desirable to know whether the results of small-scale testing are applicable to larger-sized bearings. In this work, three different bearing types were tested and compared to already published results from a small-scale ACBB with a pitch diameter of 60 mm. The newly tested bearing types comprise a downscaled blade bearing (4-point contact double row ball bearing) with a pitch diameter of 673 mm, a small-scale CRTB with a pitch diameter of 77.5 mm and another ACBB with a pitch diameter of 95 mm. Qualitatively, all tested bearings show similar wear behaviour in terms of friction energy when operation parameters are varied. With higher oscillation frequency, damage becomes more severe. The oscillation amplitude shows three distinctive regimes. Within the range of small amplitudes, an increase in amplitude leads to more pronounced damage. We observe a threshold amplitude where this is no longer the case; a further increase in amplitude counteracts wear initiation until a final threshold is reached, beyond which no more wear is observed. These findings are in accordance with the reference results of the small-scale ACBB. Direct comparison between point and line contact shows that the latter is more prone to wear initiation under grease-lubricated, oscillating operating conditions. Furthermore, a previously introduced empirical number shows good performance in assessing critical operating parameters of the different bearing types. Specifically, harmful operating conditions can be classified for all studied bearing types with an accuracy of 78%. This method can be useful to assess operating conditions of greased, oscillating, rolling element bearings, e.g., to assess different pitch controllers or designs of slewing bearings

Wear Development in Oscillating Rolling Element Bearings

Rotor blade bearings enable rotor blades to pivot about their longitudinal axis and thus control the power output and reduce the loads acting on the wind turbine. Over a design period of 20 years, rolling bearings are exposed to frequent oscillation movements with amplitude ratios of x/2b > 1, especially due to new control concepts such as Individual Pitch Control, which can lead to wear and a reduction in service life. The objective of this paper was to identify the dominant wear mechanisms and their consequences for the operation of oscillating bearings. Oscillating experiments with an increasing number of cycles on the angular contact ball bearings of two different sizes (types 7208 and 7220) show that the damage initiation starts with adhesive and corrosive wear mechanisms, which result in a sharp increase in the torque as well as the wear volume on the bearing raceway. As the number of cycles increases, an abrasive mechanism occurs, resulting in a lower slope of the wear curve and a smoothing of the resulting wear depressions. The wear and torque curves were evaluated and classified using an energy-wear approach according to Fouvry

Burst of corneal dendritic cells during Trastuzumab and Paclitaxel treatment

During breast cancer therapy, paclitaxel and trastuzumab are both associated with adverse effects such as chemotherapy-induced peripheral neuropathy and other systemic side effects including ocular complications. Corneal nerves are considered part of the peripheral nervous system and can be imaged non-invasively by confocal laser scanning microscopy (CLSM) on the cellular level. Thus, in vivo CLSM imaging of structures of the corneal subbasal nerve plexus (SNP) such as sensory nerves or dendritic cells (DCs) can be a powerful tool for the assessment of corneal complications during cancer treatment. During the present study, the SNP of a breast cancer patient was analyzed over time by using large-scale in vivo CLSM in the course of paclitaxel and trastuzumab therapy. The same corneal regions could be re-identified over time. While the subbasal nerve morphology did not alter significantly, a change in dendritic cell density and an additional local burst within the first 11 weeks of therapy was detected, indicating treatment-mediated corneal inflammatory processes. Ocular structures such as nerves and dendritic cells could represent useful biomarkers for the assessment of ocular adverse effects during cancer therapy and their management, leading to a better visual prognosis

3D confocal laser-scanning microscopy for large-area imaging of the corneal subbasal nerve plexus

The capability of corneal confocal microscopy (CCM) to acquire high-resolution in vivo images of the densely innervated human cornea has gained considerable interest in using this non-invasive technique as an objective diagnostic tool for staging peripheral neuropathies. Morphological alterations of the corneal subbasal nerve plexus (SNP) assessed by CCM have been shown to correlate well with the progression of neuropathic diseases and even predict future-incident neuropathy. Since the field of view of single CCM images is insufficient for reliable characterisation of nerve morphology, several image mosaicking techniques have been developed to facilitate the assessment of the SNP in large-area visualisations. Due to the limited depth of field of confocal microscopy, these approaches are highly sensitive to small deviations of the focus plane from the SNP layer. Our contribution proposes a new automated solution, combining guided eye movements for rapid expansion of the acquired SNP area and axial focus plane oscillations to guarantee complete imaging of the SNP. We present results of a feasibility study using the proposed setup to evaluate different oscillation settings. By comparing different image selection approaches, we show that automatic tissue classification algorithms are essential to create high-quality mosaic images from the acquired 3D dataset

Real-time large-area imaging of the corneal subbasal nerve plexus

The morphometric assessment of the corneal subbasal nerve plexus (SNP) by confocal microscopy holds great potential as a sensitive biomarker for various ocular and systemic conditions and diseases. Automated wide-field montages (or large-area mosaic images) of the SNP provide an opportunity to overcome the limited field of view of the available imaging systems without the need for manual, subjective image selection for morphometric characterization. However, current wide-field montaging solutions usually calculate the mosaic image after the examination session, without a reliable means for the clinician to predict or estimate the resulting mosaic image quality during the examination. This contribution describes a novel approach for a real-time creation and visualization of a mosaic image of the SNP that facilitates an informed evaluation of the quality of the acquired image data immediately at the time of recording. In cases of insufficient data quality, the examination can be aborted and repeated immediately, while the patient is still at the microscope. Online mosaicking also offers the chance to identify an overlap of the imaged tissue region with previous SNP mosaic images, which can be particularly advantageous for follow-up examinations

In vivo monitoring of corneal dendritic cells in the subbasal nerve plexus during Trastuzumab and Paclitaxel breast cancer therapy - a one-year follow-up

Paclitaxel and trastuzumab have been associated with adverse effects including chemotherapy-induced peripheral neuropathy (CIPN) or ocular complications. In vivo confocal laser scanning microscopy (CLSM) of the cornea could be suitable for assessing side effects since the cornea is susceptible to, i.e., neurotoxic stimuli. The study represents a one-year follow-up of a breast cancer patient including large-area in vivo CLSM of the subbasal nerve plexus (SNP), nerve function testing, and questionnaires during paclitaxel and trastuzumab therapy. Six monitoring sessions (one baseline, four during, and one after therapy) over 58 weeks were carried out. Large-area mosaics of the SNP were generated, and identical regions within all sessions were assigned. While corneal nerve morphology did not cause alterations, the number of dendritic cells (DCs) showed dynamic changes with a local burst at 11 weeks after baseline. Simultaneously, paclitaxel treatment was terminated due to side effects, which, together with DCs, returned to normal levels as the therapy progressed. Longitudinal in vivo CLSM of the SNP could complement routine examinations and be helpful to generate a comprehensive clinical picture. The applied techniques, with corneal structures acting as biomarkers could represent a diagnostic tool for the objective assessment of the severity of adverse events and the outcome

Assessment of dynamic corneal nerve changes using static landmarks by in vivo large-area confocal microscopy—a longitudinal proof-of-concept study

Background: The purpose of the present proof-of-concept study was to use large-area in vivo confocal laser scanning microscopy (CLSM) mosaics to determine the migration rates of nerve branching points in the human corneal subbasal nerve plexus (SNP). Methods: Three healthy individuals were examined roughly weekly over a total period of six weeks by large-area in vivo confocal microscopy of the central cornea. An in-house developed prototype system for guided eye movement with an acquisition time of 40 s was used to image and generate large-area mosaics of the SNP. Kobayashi-structures and nerve entry points (EPs) were used as fixed structures to enable precise mosaic registration over time. The migration rate of 10 prominent nerve fiber branching points per participant was tracked and quantified over the longitudinal period. Results: Total investigation times of 10 minutes maximum per participant were used to generate mosaic images with an average size of 3.61 mm2 (range: 3.18–4.42 mm2). Overall mean branching point migration rates of (46.4±14.3), (48.8±15.5), and (50.9±13.9) µm/week were found for the three participants with no statistically significant difference. Longitudinal analyses of nerve branching point migration over time revealed significant time-dependent changes in migration rate only in participant 3 between the last two measurements [(63.7±12.3) and (43.0±12.5) µm/week, P<0.01]. Considering individual branching point dynamics, significant differences in nerve migration rate from the mean were only found in a few exceptions. Conclusions: The results of this proof-of-concept study have demonstrated the feasibility of using in vivo confocal microscopy to study the migration rates of corneal subbasal nerves within large areas of the central human cornea (>1 mm2). The ability to monitor dynamic changes in the SNP opens a window to future studies of corneal nerve health and regenerative capacity in a number of systemic and ocular diseases. Since corneal nerves are considered part of the peripheral nervous system, this technique could also offer an objective diagnostic tool and biomarker for disease- or treatment-induced neuropathic changes