69 research outputs found
Photoinduced ordering and anchoring properties of azo-dye films
We study both theoretically and experimentally anchoring properties of
photoaligning azo-dye films in contact with a nematic liquid crystal depending
on photoinduced ordering of azo-dye molecules. In the mean field approximation,
we found that the bare surface anchoring energy linearly depends on the azo-dye
order parameter and the azimuthal anchoring strength decays to zero in the
limit of vanishing photoinduced ordering. From the absorption dichroism spectra
measured in the azo-dye films that are prepared from the azo-dye derivative
with polymerizable terminal groups (SDA-2) we obtain dependence of the dichroic
ratio on the irradiation dose. We also measure the polar and azimuthal
anchoring strengths in nematic liquid crystal (NLC) cells aligned by the
azo-dye films and derive the anchoring strengths as functions of the dichroic
ratio. Though linear fitting of the experimental data for both anchoring
strengths gives reasonably well results, it, in contradiction with the theory,
predicts vanishing of the azimuthal anchoring strength at certain nonzero value
of the azo-dye order parameter. By using a simple phenomenological model we
show that this discrepancy can be attributed to the difference between the
surface and bulk order parameters in the films.Comment: revtex4, 25 pages, 9 figure
RAF Kinase Activity Regulates Neuroepithelial Cell Proliferation and Neuronal Progenitor Cell Differentiation during Early Inner Ear Development
Background: Early inner ear development requires the strict regulation of cell proliferation, survival, migration and differentiation, coordinated by the concerted action of extrinsic and intrinsic factors. Deregulation of these processes is associated with embryonic malformations and deafness. We have shown that insulin-like growth factor I (IGF-I) plays a key role in embryonic and postnatal otic development by triggering the activation of intracellular lipid and protein kinases. RAF kinases are serine/threonine kinases that regulate the highly conserved RAS-RAF-MEK-ERK signaling cascade involved in transducing the signals from extracellular growth factors to the nucleus. However, the regulation of RAF kinase activity by growth factors during development is complex and still not fully understood.
Methodology/Principal Findings: By using a combination of qRT-PCR, Western blotting, immunohistochemistry and in situ hybridization, we show that C-RAF and B-RAF are expressed during the early development of the chicken inner ear in specific spatiotemporal patterns. Moreover, later in development B-RAF expression is associated to hair cells in the sensory patches. Experiments in ex vivo cultures of otic vesicle explants demonstrate that the influence of IGF-I on proliferation but not survival depends on RAF kinase activating the MEK-ERK phosphorylation cascade. With the specific RAF inhibitor Sorafenib, we show that blocking RAF activity in organotypic cultures increases apoptosis and diminishes the rate of cell proliferation in the otic epithelia, as well as severely impairing neurogenesis of the acoustic-vestibular ganglion (AVG) and neuron maturation.
Conclusions/Significance: We conclude that RAF kinase activity is essential to establish the balance between cell proliferation and death in neuroepithelial otic precursors, and for otic neuron differentiation and axonal growth at the AVG
Regulation of cellular proliferation, differentiation and cell death by activated Raf
The protein kinases Raf-1, A-Raf and B-Raf connect receptor stimulation with intracellular signaling pathways and function as a central intermediate in many signaling pathways. Gain-of-function experiments shed light on the pleiotropic biological activities of these enzymes. Expression experiments involving constitutively active Raf revealed the essential functions of Raf in controlling proliferation, differentiation and cell death in a cell-type specific manner
Potential therapeutic applications of microbial surface-activecompounds
Numerous investigations of microbial surface-active compounds or biosurfactants over the past two decades have led to the discovery of many interesting physicochemical and biological properties including antimicrobial, anti-biofilm and therapeutic among many other pharmaceutical and medical applications. Microbial control and inhibition strategies involving the use of antibiotics are becoming continually challenged due to the emergence of resistant strains mostly embedded within biofilm formations that are difficult to eradicate. Different aspects of antimicrobial and anti-biofilm control are becoming issues of increasing importance in clinical, hygiene, therapeutic and other applications. Biosurfactants research has resulted in increasing interest into their ability to inhibit microbial activity and disperse microbial biofilms in addition to being mostly nontoxic and stable at extremes conditions. Some biosurfactants are now in use in clinical, food and environmental fields, whilst others remain under investigation and development. The dispersal properties of biosurfactants have been shown to rival that of conventional inhibitory agents against bacterial, fungal and yeast biofilms as well as viral membrane structures. This presents them as potential candidates for future uses in new generations of antimicrobial agents or as adjuvants to other antibiotics and use as preservatives for microbial suppression and eradication strategies
Lectin binding patterns in normal canine endometrium and in bitches with pyometra and cystic endometrial hyperplasia
Cystic endometrial hyperplasia (CEH) and
pyometra in the bitch are dioestral syndromes, supposed
to be caused by hormonal disturbances and changes in
endometrial steroid hormone receptor levels.
Histologically, the endometria show cystic dilated glands
and, if bacteria succeed in invading the uterus, pyometra
may develop in the following metoestrus. In this study,
lectin histochemistry was performed on paraffin sections
to compare carbohydrate expression of uterine glands
and surface epithelium in healthy dogs and in dogs with
CEH and pyometra. Lectin binding is a useful tool to
identify glycoconjugates, especially of the glycocalyx,
which has essential functions in the endometrium during
reproduction. Uterine tissue was obtained from 18
healthy bitches in metoestrus or anoestrus and 18 bitches
with a clinical diagnosis of CEH or pyometra. Normal
endometria showed cycle-dependent changes in SBA,
PNA, HPA and UEA binding during metoestrus and
anoestrus. LCA did not show cycle-dependent changes
and WGA bound to Golgi regions in the apical parts of
surface epithelial cells only in metoestrous. Endometria
with inflammatory alterations lost cycle-specific lectin
binding patterns and, with increasing severity of
pathological changes, showed a marked decrease in binding intensity to the glandular and surface epithelial
glycocalyx and secretions. In dogs with CEH, unaltered
glands with generally strong lectin binding to the
glycocoalyx and Golgi regions were found adjacent to
altered glands. The decrease of lectin binding in
pyometra cases is supposed to be a result of glandular
exhaustion after cystic hyperplasia. In addition, bacterial
adhesion to sugar residues on the uterine surface
epithelium might impede lectin binding
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