507 research outputs found
A Solvable Model for Polymorphic Dynamics of Biofilaments
We investigate an analytically tractable toy model for thermally induced
polymorphic dynamics of cooperatively rearranging biofilaments - like
microtubules. The proposed 4 -block model, which can be seen as a
coarse-grained approximation of the full polymorphic tube model, permits a
complete analytical treatment of all thermodynamic properties including
correlation functions and angular fourier mode distributions. Due to its
mathematical tractability the model straightforwardly leads to some physical
insights in recently discussed phenomena like the "length dependent persistence
length". We show that a polymorphic filament can disguise itself as a classical
worm like chain on small and on large scales and yet display distinct anomalous
tell-tale features indicating an inner switching dynamics on intermediate
length scales
The Controversial History of Hormone Replacement Therapy
The history of hormone replacement therapy (HRT) started in the 1960s, with very high popularity in the 1990s. The first clinical trials on HRT and chronic postmenopausal conditions were started in the USA in the late 1990s. After the announcement of the first results of the Women's Health Initiative (WHI) in 2002, which showed that HRT had more detrimental than beneficial effects, HRT use dropped. The negative results of the study received wide publicity, creating panic among some users and new guidance for doctors on prescribing HRT. The clear message from the media was that HRT had more risks than benefits for all women. In the following years, a reanalysis of the WHI trial was performed, and new studies showed that the use of HRT in younger women or in early postmenopausal women had a beneficial effect on the cardiovascular system, reducing coronary disease and all-cause mortality. Notwithstanding this, the public opinion on HRT has not changed yet, leading to important negative consequences for women's health and quality of life
Sine-Gordon solitons, auxiliary fields, and singular limit of a double pendulums chain
We consider the continuum version of an elastic chain supporting topological
and non-topological degrees of freedom; this generalizes a model for the
dynamics of DNA recently proposed and investigated by ourselves. In a certain
limit, the non-topological degrees of freedom are frozen, and the model reduces
to the sine-Gordon equations and thus supports well-known topological soliton
solutions. We consider a (singular) perturbative expansion around this limit
and study in particular how the non-topological field assume the role of an
auxiliary field. This provides a more general framework for the slaving of this
degree of freedom on the topological one, already observed elsewhere in the
context of the mentioned DNA model; in this framework one expects such
phenomenon to arise in a quite large class of field-theoretical models.Comment: 18 pages, 2 figure
Ospemifene in the management of vulvar and vaginal atrophy: Focus on the assessment of patient acceptability and ease of use
Endocrinological changes that occur with menopause lead to a chronic and progressive condition named vulvar and vaginal atrophy (VVA). This disease is characterized by symptoms such as dryness, dyspareunia, itching, burning, and dysuria. According to recent epidemiological studies, VVA has a high prevalence and can also occur in younger women prior to the menopause, negatively affecting quality of life, sexual function, intimacy and relationship with the partner. Accordingly, therapy should be effective, initiated early and continued for as long as possible. Up to recent years, available therapeutic options have included over-the-counter lubricants and moisturizers, vaginal oestrogens and systemic hormones. These products are not indicated for all women. Hormones are mostly contraindicated in women with a history of hormone-sensitive cancer and are frequently not accepted even by women without contraindications. Local therapies are frequently considered uncomfortable, difficult to apply, and messy. Indeed, these treatments have a high spontaneous discontinuation rate, mostly due to dissatisfaction, safety concern, side effects and difficulty in vaginal placement. Recently, ospemifene, a new non-hormonal systemic remedy, was approved by FDA (Food and Drug Administration) and EMA (European Medicines Agency) for the treatment of the two most bothersome symptoms of VVA: dryness and dyspareunia. Because ospemifene is a selective estrogen receptor modulator (SERM), it can be administered also in women with a history of breast cancer, and this makes it more acceptable by any woman. In addition, its route of administration minimizes those bothersome side effects intrinsic to the vaginal route of administration. Available data indicate that women using ospemifene have higher adherence to treatment, higher persistence and lower discontinuation rate. Satisfaction is higher than with other local therapies and overall health care cost is lower
Scaffolds for controlled release of cartilage growth factors
In recent years, cell-based therapies using adult stem cells have attracted considerable interest in regenerative medicine. A tissue-engineered construct for cartilage repair should provide a support for the cell and allow sustained in situ delivery of bioactive factors capable of inducing cell differentiation into chondrocytes. Pharmacologically active microcarriers (PAMs), made of biodegradable and biocompatible poly (d,l-lactide-co-glycolide acid) (PLGA), are a unique system which combines these properties in an adaptable and simple microdevice. This device relies on nanoprecipitation of proteins encapsulated in polymeric microspheres with a solid in oil in water emulsion-solvent evaporation process, and their subsequent coating with extracellular matrix protein molecules. Here, we describe their preparation process, and some of their characterization methods for an application in cartilage tissue engineering
The Conjugated-Circuit Model: Application to Benzenoid Hydrocarbon Radicals
We have applied the conjugated-circuit model to benzenoid hydrocarbon radicals and predicted their aromatic stabilities.
Our predictions are supported by alternative theoretical schemes
such as the structure-resonance approach and by available experimental
data. This work points to a considerable potential of the conjugated-circuit model for qualitative and quantitative discussion of thermodynamic stabilities of polycyclic conjugated radicals
The Conjugated-Circuit Model: Application to Benzenoid Hydrocarbon Radicals
We have applied the conjugated-circuit model to benzenoid hydrocarbon radicals and predicted their aromatic stabilities.
Our predictions are supported by alternative theoretical schemes
such as the structure-resonance approach and by available experimental
data. This work points to a considerable potential of the conjugated-circuit model for qualitative and quantitative discussion of thermodynamic stabilities of polycyclic conjugated radicals
Helices at Interfaces
Helically coiled filaments are a frequent motif in nature. In situations
commonly encountered in experiments coiled helices are squeezed flat onto two
dimensional surfaces. Under such 2-D confinement helices form "squeelices" -
peculiar squeezed conformations often resembling looped waves, spirals or
circles. Using theory and Monte-Carlo simulations we illuminate here the
mechanics and the unusual statistical mechanics of confined helices and show
that their fluctuations can be understood in terms of moving and interacting
discrete particle-like entities - the "twist-kinks". We show that confined
filaments can thermally switch between discrete topological twist quantized
states, with some of the states exhibiting dramatically enhanced
circularization probability while others displaying surprising
hyperflexibility
Analysis of salinity tolerance of Vitis vinifera 'Thompson Seedless' transformed with AtNHX1
Several transgenic plant species expressing AtNHX1, coding for a vacuolar Na+/H+ antiporter from Arabidopsis thaliana, have shown their ability to cope with salinity. The aim of this study was to analyze the response of Vitis vinifera cv. 'Thompson Seedless' transformed with AtNHX1 to salt stress, using soil substrate or hydroponic media, and to compare the response with untransformed 'Thompson Seedless' and allegedly tolerant 'Criolla' cultivars: 'Pedro Giménez' and 'Criolla Chica'. 'Thompson Seedless' embryogenic calli were transformed with Agrobacterium tumefaciens carrying AtNHX1 under the control of CaMV 35S promoter. Transgenic and untransformed plants were grown in a greenhouse under hydroponics or in pots with soil, and were subjected to increasing concentrations of sodium chloride (NaCl) up to 150 mM for a period of 7 weeks. Growth and toxicity symptoms were less affected in transgenics as compared to the untransformed grapevines, and transgenic lines had higher shoot length, leaf area and dry weights at the end of the experiment. Root concentrations of Na in transgenics were similar or lower than that observed in untransformed genotypes. Growth impairment and toxicity symptoms were observed in all genotypes under both conditions, but effects were more severe in plants growing with hydroponic culture. Potassium content and shoot to root dry weight ratio decreased with NaCl in hydroponics but not in pots. 'Criolla' cultivars grew less than the other genotypes, although 'Pedro Giménez' always exhibited highest shoot/root ratios
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