Numerical and experimental analysis of vortex sheets behind lifting surfaces

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77273/1/AIAA-1992-409-534.pd

Characterization of sequences and mechanisms through which ISE/ISS-3 regulates FGFR2 splicing

Alternative splicing of fibroblast growth factor receptor-2 (FGFR2) mutually exclusive exons IIIb and IIIc results in highly cell-type-specific expression of functionally distinct receptors, FGFR2-IIIb and FGFR2-IIIc. We previously identified an RNA cis-element, ISE/ISS-3, that enhanced exon IIIb splicing and silenced exon IIIc splicing. Here, we have performed comprehensive mutational analysis to define critical sequence motifs within this element that independently either enhance splicing of upstream exons or repress splicing of downstream exons. Such analysis included use of a novel fluorescence-based splicing reporter assay that allowed quantitative determination of relative functional activity of ISE/ISS-3 mutants using flow cytometric analysis of live cells. We determined that specific sequences within this element that mediate splicing enhancement also mediate splicing repression, depending on their position relative to a regulated exon. Thus, factors that bind the element are likely to be coordinately involved in mediating both aspects of splicing regulation. Exon IIIc silencing is dependent upon a suboptimal branchpoint sequence containing a guanine branchpoint nucleotide. Previous studies of exon IIIc splicing in HeLa nuclear extracts demonstrated that this guanine branchsite primarily impaired the second step of splicing suggesting that ISE/ISS-3 may block exon IIIc inclusion at this step. However, results presented here that include use of newly developed in vitro splicing assays of FGFR2 using extracts from a cell line expressing FGFR2-IIIb strongly suggest that cell-type-specific silencing of exon IIIc occurs at or prior to the first step of splicing

The 'alternative' EMT switch

Epithelial to mesenchymal transition (EMT) is an essential process in embryonic development and is aberrantly induced in many disease settings. Work carried out by Chonghui Cheng's laboratory addressed the involvement of alternative RNA splicing in EMT and its link to tumour progression. They describe a switch in CD44 expression from variant isoform(s) to the standard isoform and showed, for the first time, that this is required for normal epithelial cells to undergo EMT. In addition, they link expression of the CD44 standard isoform with high-grade breast cancer and to activation of the phosphoinositide 3-kinase/Akt pathway and apoptosis resistance in a mouse model of recurrent disease

Assessment of Different Expression Strategies for the Production of a Recombinant Lipoprotein Vaccine in Plants

The ability of plants to serve as a production system for bacterial lipoprotein vaccines has been investigated. First, the effect of high-level expression of the Borrelia burgdorferi outer membrane protein A (OspA), a prototype vaccine against Lyme disease, has been examined by a proteomics approach. Analysis by 2D-PAGE of wild type tobacco plants and transplastomic plants accumulating recombinant OspA showed no apparent differences in protein pattern except for OspA. However, presence of the bacterial signal sequence limits transgene accumulation. As an alternative approach OspA was produced in Nicotiana benthamiana plants by transient expression via a deconstructed tobacco mosaic virus-based system. While rapid expression of OspA could be achieved, no palmitoylation occurred with the genuine bacterial sequence. In contrast, modification of the N-terminus with an eukaryotic sequence motif resulted in palmitoylation of OspA. This study shows that plants provide multiple expression strategies and could serve as a versatile production platform for recombinant lipidated subunit vaccines

Polymorph screening studies of oxcarbazepine : twisted habit in crystals of the elusive form III

Crystal structures exhibiting twisted morphology have been observed at the nanoscale, mesoscale, and macroscale and are challenging to characterise structurally because of their lack of long-range translational symmetry [1]. Crystal structure prediction (CSP) studies of an active pharmaceutical ingredient’s lattice energy landscape are often utilised for assisting experimentalists in identifying and characterising novel polymorphic forms that are thermodynamically feasible, including ones that crystallise with twisted morphologies [2-4]. Oxcarbazepine (OXCBZ) is a commercially available pharmaceutical used for the treatment of epilepsy and three polymorphic forms have been reported, two of which (form I and form II) are known to crystallise in the monoclinic space groups P21/c and P21 respectively [5]. Form III of OXCBZ was originally prepared by slow evaporation from methanol solutions that contained polymer additives but structure solution was not possible because of the small size and poor quality of the crystals. Herein, we present experimental protocols for the crystallization of OXCBZ III from both solution and the vapour phase. In our work, we combined CSP studies of OXCBZ with physical vapour deposition studies and solution-based polymorph screening experiments. Needle-like and fibre-like crystals of OXCBZ III exhibiting variable twisted habit emerged from vapour deposition of OXCBZ onto metallic substrates. Scanning electron and atomic force microscopy studies have been carried out to obtain an insight into the mechanism of formation and growth of the twisted OXCBZ III crystals over the course of the deposition process

Oxcarbazepine form III : observation of twisted habit in crystals of an elusive pharmaceutical polymorph

Crystals exhibiting twisted habit have been observed at the nanoscale, mesoscale, and macroscale and pose challenges with respect to structural characterisation because of their lack of long-range translational symmetry [1]. Crystal structure prediction (CSP) investigations of an active pharmaceutical ingredient’s lattice energy landscape are a potent tool for assisting experimentalists in identifying and characterising novel polymorphic forms that are thermodynamically feasible, including ones that crystallise with twisted morphologies [2-4]. Oxcarbazepine (OXCBZ) is a pharmaceutical used for the treatment of epileptic seizures and three polymorphic forms have been reported, two of which (form I and form II) crystallise in the monoclinic space groups P21/c and P21 respectively [5]. OXCBZ form III was originally prepared by slow evaporation from methanol solutions containing polymer additives but structure determination was not possible because of the small size and poor quality of the crystals produced. Herein, we present robust protocols for the crystallisation of OXCBZ III from both solution and the vapour phase. Our efforts combined CSP studies of OXCBZ with physical vapour deposition and solution-based polymorph screening experiments. Needle-like and fibre-like crystals of form III exhibiting variable twisted habit were serendipitously obtained through vapour deposition of OXCBZ onto metallic substrates. By performing scanning electron and atomic force microscopy investigations we have managed to gain insight into the mechanism of formation and growth of the twisted OXCBZ III crystals over the course of the deposition process

Function of a Fly Motion-Sensitive Neuron Matches Eye Movements during Free Flight

Sensing is often implicitly assumed to be the passive acquisition of information. However, part of the sensory information is generated actively when animals move. For instance, humans shift their gaze actively in a sequence of saccades towards interesting locations in a scene. Likewise, many insects shift their gaze by saccadic turns of body and head, keeping their gaze fixed between saccades. Here we employ a novel panoramic virtual reality stimulator and show that motion computation in a blowfly visual interneuron is tuned to make efficient use of the characteristic dynamics of retinal image flow. The neuron is able to extract information about the spatial layout of the environment by utilizing intervals of stable vision resulting from the saccadic viewing strategy. The extraction is possible because the retinal image flow evoked by translation, containing information about object distances, is confined to low frequencies. This flow component can be derived from the total optic flow between saccades because the residual intersaccadic head rotations are small and encoded at higher frequencies. Information about the spatial layout of the environment can thus be extracted by the neuron in a computationally parsimonious way. These results on neuronal function based on naturalistic, behaviourally generated optic flow are in stark contrast to conclusions based on conventional visual stimuli that the neuron primarily represents a detector for yaw rotations of the animal

The Natural Variation of a Neural Code

The way information is represented by sequences of action potentials of spiking neurons is determined by the input each neuron receives, but also by its biophysics, and the specifics of the circuit in which it is embedded. Even the “code” of identified neurons can vary considerably from individual to individual. Here we compared the neural codes of the identified H1 neuron in the visual systems of two families of flies, blow flies and flesh flies, and explored the effect of the sensory environment that the flies were exposed to during development on the H1 code. We found that the two families differed considerably in the temporal structure of the code, its content and energetic efficiency, as well as the temporal delay of neural response. The differences in the environmental conditions during the flies' development had no significant effect. Our results may thus reflect an instance of a family-specific design of the neural code. They may also suggest that individual variability in information processing by this specific neuron, in terms of both form and content, is regulated genetically

CD44 Upregulation in E-Cadherin-Negative Esophageal Cancers Results in Cell Invasion

E-cadherin is frequently lost during epithelial-mesenchymal transition and the progression of epithelial tumorigenesis. We found a marker of epithelial-mesenchymal transition, CD44, upregulated in response to functional loss of E-cadherin in esophageal cell lines and cancer. Loss of E-cadherin expression correlates with increased expression of CD44 standard isoform. Using an organotypic reconstruct model, we show increased CD44 expression in areas of cell invasion is associated with MMP-9 at the leading edge. Moreover, Activin A increases cell invasion through CD44 upregulation after E-cadherin loss. Taken together, our results provide functional evidence of CD44 upregulation in esophageal cancer invasion