Elastic properties of solid nematics Hovakimyan, M. T.; Sargsyan, M. L.; Hakobyan, R. S. ...
Molecular Crystals and Liquid Crystals,
05/2021, Letnik:
713, Številka:
1
Journal Article
Recenzirano
The general approach to study the properties of the mechanical deformations of solid nematics, which are the macroscopic homogeneous elastic media having the rotational symmetry of the nematic liquid ...crystals is proposed. The stress tensor, the Young modulus and the Poisson ratios for the parallel and perpendicular homogeneous orientations of nematic molecules relative to the axis of external forces influence are obtained by the varying of the free energy of mechanical deformation. It is shown that these constants have the anisotropic character and the experiments for the direct measurement of five elasticity coefficients entering the free energy expression are proposed.
Highlights • Standard behavioral tests were successfully applied to NPC1−/− mutant mice. • The mutant mice revealed defective motor performance and cognitive impairment. • The motor impairment was in ...agreement with Purkinje cell degeneration in the cerebellum. • The motor performance improved significantly upon combined therapy. • The impaired cognitive function, however, did not benefit from the treatment.
PurposeThis study was designed to compare and contrast quantitative data of the human corneal sub-basal nerve plexus (SBP) evaluated by two different methods: in vivo confocal microscopy (IVCM), and ...immunohistochemical staining of ex vivo donor corneas.MethodsSeven parameters of the SBP in large-scale IVCM mosaicking images from healthy subjects were compared with the identical parameters in ex vivo donor corneas stained by β-III-tubulin immunohistochemistry. Corneal nerve fiber length (CNFL), corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), average weighted corneal nerve fiber tortuosity (CNFTo), corneal nerve connection points (CNCP), average corneal nerve single-fiber length (CNSFL), and average weighted corneal nerve fiber thickness (CNFTh) were calculated using a dedicated, published algorithm and compared.ResultsOur experiments showed significantly higher values for CNFL (50.2 vs 21.4 mm/mm
), CNFD (1358.8 vs 277.3 nerve fibers/mm
), CNBD (847.6 vs 163.5 branches/mm
), CNFTo (0.095 vs 0.081 μm
), and CNCP (49.4 vs 21.6 connections/mm
) in histologically staining specimens compared with IVCM images. In contrast, CNSFL values were higher in IVCM images than in histological specimens (32.1 vs 74.1 μm). No significant difference was observed in CNFTh (2.22 vs 2.20 μm) between the two groups.ConclusionsThe results of this study have shown that IVCM has an inherently lower resolution compared with ex vivo immunohistochemical staining of the corneal SBP and that this limitation leads to a systematic underestimation of several SBP parameters. Despite this shortcoming, IVCM is a vital clinical tool for in vivo characterization, quantitative clinical imaging, and evaluation of the human corneal SBP.
Summary
Assessment of various morphological parameters of the corneal subbasal nerve plexus is a valuable method of documenting the structural and presumably functional integrity of the corneal ...innervation in health and disease. The aim of this work is to establish a rapid, reliable and reproducible method for visualization of the human corneal SBP using femtosecond laser cut corneal tissue sections. Trephined healthy corneal buttons were fixed and processed using TissueSurgeon—a femtosecond laser based microtome, to obtain thick tissue sections of the corneal epithelium and anterior stroma cut parallel to the ocular surface within approximately 15 min. A near infrared femtosecond laser was focused on to the cornea approximately 70–90 μm from the anterior surface to induce material separation using TissueSurgeon. The obtained corneal sections were stained following standard immunohistochemical procedures with anti‐neuronal β‐III tubulin antibody for visualization of the corneal nerves. Sections that contained the epithelium and approximately 20–30 μm of anterior stroma yielded excellent visualisation of the SBP with minimal optical interference from underlying stromal nerves. In conclusion, the results of this study have demonstrated that femtosecond laser cutting of the human cornea offers greater speed, ease and reliability than standard tissue preparation methods for obtaining high quality thick sections of the anterior cornea cut parallel to the ocular surface.
Lay description
Human cornea is one of the most highly innervated tissues in the body. Sectioning of the cornea for the quantitative analysis of its innervation by immunohistochemistry is necessary during health and disease. Attempts to obtain frozen or paraffin‐sections of whole corneas parallel to the plane of its innervation are technically challenging and also time consuming due to the curvature of the tissue. In an effort to overcome this difficulty, here we report a contact‐free and rapid femtosecond laser based cutting method to obtain high quality surface parallel sections of the human cornea in less than 15 min. Furthermore, femtosecond based laser microtomy can be adopted easily for sectioning of all kind of biological samples including hard tissues (teeth and bone) and offers a more standardized way of tissue sectioning by avoiding the laborious processes of sample preparation and embedding thereby preventing the loss of valuable tissue sample.
Use of Brillouin spectroscopy in ophthalmology enables noninvasive, spatially resolved determination of the rheological properties of crystalline lens tissue. Furthermore, the Brillouin shift ...correlates with the protein concentration inside the lens. In vitro measurements on extracted porcine lenses demonstrate that results obtained with Brillouin spectroscopy depend strongly on time after death. The intensity of the Brillouin signal decreases significantly as early as 5 h postmortem. Moreover, the fluctuation of the Brillouin frequency shift inside the lens increases with postmortem time. Images of lens tissue taken with a confocal reflectance microscope between measurements reveal a degenerative aging process. These tissue changes correlate with our results from Brillouin spectroscopy. It is concluded that only in vivo measurements appropriately reflect the rheological properties of the eye lens and its protein concentration.
Functional replacement of specific neuronal populations through transplantation of neural tissue represents an attractive therapeutic strategy for treating neurodegenerative disorders like ...Parkinson's disease (PD). Even though the brain is a partially immune privileged site, immunosuppression is still needed for the prevention of host immune response, and thus, xenograft rejection. Here, we investigated the fate of human ventral mesencephalon derived immortalized cell line ReNcell VM upon unilateral transplantation into the intact rat striatum with or without immunosuppression with cyclosporine A (CsA).
The status of xenografted human ReNcell VM cells was analysed by immunohistochemistry/immunofluorescence 4 and 6weeks after transplantation.
Four weeks after transplantation, ReNcell VM cells could be detected in both groups, although the number of survived cells was significantly higher in brains of immunosuppressed rats. In contrast, only 2 out of 6 brains grafted without immunosuppression revealed human ReNcell VM cells 6weeks post grafting, whereas a considerable number of human cells could still be found in all the brains of immunosuppressed rats. Immunohistochemical analysis of grafted cells showed almost no evidence of neuronal differentiation, but rather astroglial development.
In summary, we have shown that the immunosuppression is needed for the survival of human VM derived progenitor cells in the rat striatum. CsA affected cell survival, but not differentiation capacity: in both groups, grafted either with or without immunosuppression, the ReNcell VM cells lacked neuronal phenotype and developed preferentially into astroglia.
Background. The increased antiretroviral therapy (ART) coverage of patients in the absence of routine drug resistance (DR) tests highlight the importance of HIV-1 drug resistance surveillance in ...Armenia. Aim. The aim of this study was a determination of the prevalence of HIV-1 DR on a large-scale cohort of HIV-infected citizens of the Republic of Armenia who had no experience of taking antiretroviral drugs. Materials and methods. The study was carried out on a cohort of more than 20% of PLHIV in the Republic of Armenia. The resulting 982 nucleotide sequences of the HIV-1 pol gene fragment, encoding the protease and reverse transcriptase region, as well as 367 sequences of the integrase gene, were analyzed using the Stanford University database and the CPR tool for the presence of drug resistance mutations and determination of the resistance level to ARV drugs. The HIV-1 subtype was determined using the Stanford University database and confirmed by phylogenetic analysis. Results. The overall prevalence of HIV DR to ARV drugs in naïve patients was 13.8%. Resistance to non-nucleoside reverse transcriptase inhibitors was 11.2%, nucleotide reverse transcriptase inhibitors — 1.4%, protease inhibitors — 2.0% and integrase inhibitors — 0.5%. The predominant genetic variant among viruses containing DR mutations was subtype B. Resistance was most often recorded among men who have sex with men living in Yerevan. Conclusion. In our study, prevalence of DR was high only for the NNRTI drugs. The results show that the first-line ARV drugs recommended in current national guidelines are highly likely to be effective. The analysis was carried out on a significant proportion of HIV-infected citizens of the Republic of Armenia, which increases the reliability and accuracy of the data obtained.
The implementation of additional modalities for tear film break-up time characterisation expands the application range of the Oculus® Keratograph 5M. The aim of the present study was to evaluate the ...possibilities for non-invasive break-up time analysis using this device. Furthermore we applied the Oculus® Keratograph 5M to characterise possible modifications of tear break-up time after application of Thealoz® eye drops (Théa Pharma). The device allowed for a precise and solid topographical analysis of tear film dynamics. We could show that at four weeks after treatment, trehalose solution was a better treatment for dry eye compared with saline. These results are in agreement with our previous in vitro findings concerning the protective role of trehalose on desiccation-caused cell death in a corneal epithelial model.
In vitro expanded neural precursor cells could provide a renewable source of dopaminergic (DAergic) neurons for cell replacement therapy. In the present study immortalized cell line CSM14.1 was ...investigated in vitro. Cells were derived from the ventral mesencephalic area of a 14-day-old rat embryo and immortalized retrovirally with the temperature-sensitive mutant of the SV40 Large T-antigen. We investigate the proliferation and differentiation of these cells under various culture conditions, at different temperatures and serum conditions. For differentiation were propagated cells at 39 degrees C in medium supplemented with 1% FCS with or without cytokines. At chosen time points cells were investigated for the expression of different markers by western blot and immunocytochemistry. As controls cells cultured at 33 degrees C with 10% FCS for 3 days were used. We have shown that serum reduction alone is not sufficient for CSM14.1-cells to stop proliferating and begin differentiation. Following serum reduction and elevation of the temperature cells changed their morphology began to express specific band of the neuronal marker NeuN. Following cytokines treatment the mean length of cellular processes increased from 319 to 385 microm per cell, whereas the expression of neuronal markers such as NeuN and TH was not markedly changed. In conclusion, the differentiation cocktail consisting of interleukin 1(Il-1), Il-11, leukaemia inhibitory factor (LIF) and GDNF, does influence the outgrowth of neuritis but does not change the expression of mature neuronal markers at the protein level in CSM14.1 cells.
Confocal in vivo laser scanning microscopy is an established technique to visualise morphology of the cornea and conjunctiva, whereby the image interpretation needs experience. We report about ...changes of the ocular surface in the pathological conditions of infectious, metabolic and traumatic genesis and discuss their relevance. The micromorphology of the corneal epithelium and stroma in respect to pathogens (bacterial, fungal) is discussed. Metabolic disease induces multifaceted corneal alterations which can be visualised and used for assessment of the disease progression. Follow-up microscopic investigations allow for an assessment of the wound healing dynamics and enable a prognosis to be made for corneal recurrence. Taken together, confocal in vivo microscopy allows a non-invasive microscopy on the cellular level and thus complements clinical diagnostics.
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