Viscoelastic response of contractile filament bundles

The actin cytoskeleton of adherent tissue cells often condenses into filament bundles contracted by myosin motors, so-called stress fibers, which play a crucial role in the mechanical interaction of cells with their environment. Stress fibers are usually attached to their environment at the endpoints, but possibly also along their whole length. We introduce a theoretical model for such contractile filament bundles which combines passive viscoelasticity with active contractility. The model equations are solved analytically for two different types of boundary conditions. A free boundary corresponds to stress fiber contraction dynamics after laser surgery and results in good agreement with experimental data. Imposing cyclic varying boundary forces allows us to calculate the complex modulus of a single stress fiber.Comment: Revtex with 24 pages, 7 Postscript figures included, accepted for publication in Phys. Rev.

Frequency Dispersion of Sound Propagation in Rouse Polymer Melts via Generalized Dynamic Random Phase Approximation

An extended generalization of the dynamic random phase approximation (DRPA) for L-component polymer systems is presented. Unlike the original version of the DRPA, which relates the (LxL) matrices of the collective density-density time correlation fumctions and the corresponding susceptibilities of polymer concentrated systems to those of the tracer macromolecules and so-called broken links system (BLS), our generalized DRPA solves this problem for (5xL)x(5xL) matrices of the coupled susceptibilities and time correlation functions of the component number, kinetic energy and flux densities. The presented technique is used to study propagation of sound and dynamic form-factor in disentangled (Rouse) monodisperse homopolymer melt. The calculated sound velocity and absorption coefficient reveal substantial frequency dispersion. The relaxation time is found to be N times less than the Rouse time (N is the degree of polymerization), which evidences strong dynamic screening because of interchain interaction. We discuss also some peculiarities of the Brillouin scattering in polymer melts. Besides, a new convenient expression for the dynamic structural function of the Rouse chain in (q,p)-representation is found.Comment: 37 pages, 2 appendices, 48 references, 1 figur

Improving access to emergent spinal care through knowledge translation : an ethnographic study

Background: For patients and family members, access to timely specialty medical care for emergent spinal conditions is a significant stressor to an already serious condition. Timing to surgical care for emergent spinal conditions such as spinal trauma is an important predictor of outcome. However, few studies have explored ethnographically the views of surgeons and other key stakeholders on issues related to patient access and care for emergent spine conditions. The primary study objective was to determine the challenges to the provision of timely care as well as to identify areas of opportunities to enhance care delivery. Methods: An ethnographic study of key administrative and clinical care providers involved in the triage and care of patients referred through CritiCall Ontario was undertaken utilizing standard methods of qualitative inquiry. This comprised 21 interviews with people involved in varying capacities with the provision of emergent spinal care, as well as qualitative observations on an orthopaedic/neurosurgical ward, in operating theatres, and at CritiCall Ontario’s call centre. Results: Several themes were identified and organized into categories that range from inter-professional collaboration through to issues of hospital-level resources and the role of relationships between hospitals and external organizations at the provincial level. Underlying many of these issues is the nature of the medically complex emergent spine patient and the scientific evidentiary base upon which best practice care is delivered. Through the implementation of knowledge translation strategies facilitated from this research, a reduction of patient transfers out of province was observed in the one-year period following program implementation. Conclusions: Our findings suggest that competing priorities at both the hospital and provincial level create challenges in the delivery of spinal care. Key stakeholders recognized spinal care as aligning with multiple priorities such as emergent/critical care, medical through surgical, acute through rehabilitative, disease-based (i.e. trauma, cancer), and wait times initiatives. However, despite newly implemented strategies, there continues to be increasing trends over time in the number of spinal CritiCall Ontario referrals. This reinforces the need for ongoing inter-professional efforts in care delivery that take into account the institutional contexts that may constrain individual or team efforts

Altered translation of GATA1 in Diamond-Blackfan anemia

Ribosomal protein haploinsufficiency occurs in diverse human diseases including Diamond-Blackfan anemia (DBA)[superscript 1, 2], congenital asplenia[superscript 3] and T cell leukemia[superscript 4]. Yet, how mutations in genes encoding ubiquitously expressed proteins such as these result in cell-type– and tissue-specific defects remains unknown[superscript 5]. Here, we identify mutations in GATA1, encoding the critical hematopoietic transcription factor GATA-binding protein-1, that reduce levels of full-length GATA1 protein and cause DBA in rare instances. We show that ribosomal protein haploinsufficiency, the more common cause of DBA, can lead to decreased GATA1 mRNA translation, possibly resulting from a higher threshold for initiation of translation of this mRNA in comparison with other mRNAs. In primary hematopoietic cells from patients with mutations in RPS19, encoding ribosomal protein S19, the amplitude of a transcriptional signature of GATA1 target genes was globally and specifically reduced, indicating that the activity, but not the mRNA level, of GATA1 is decreased in patients with DBA associated with mutations affecting ribosomal proteins. Moreover, the defective hematopoiesis observed in patients with DBA associated with ribosomal protein haploinsufficiency could be partially overcome by increasing GATA1 protein levels. Our results provide a paradigm by which selective defects in translation due to mutations affecting ubiquitous ribosomal proteins can result in human disease.National Institutes of Health (U.S.) (Grant P01 HL32262)National Institutes of Health (U.S.) (Grant U54 HG003067-09

Thermal imaging diagnostics in stomatology

Thermal imaging diagnostics (thermography) is a high-precision method that allows identifying a pathological process at the preclinical stage by infrared radiation. For the maxillofacial region, this method may be one of the methods for choosing an additional diagnostic of the patient. Thermography has a large number of positive characteristics: safety of manipulation for the patient and the doctor; high reliability (up to 80%); speed and simplicity of research; the opportunity at one doctor’s appointment to examine the entire maxillofacial region; the possibility of dynamic observation; low cost of research. The difficulty of using this method lies only in interpreting the results, since external factors (superficially located vessels, age of the patient, thickness of subcutaneous fat, fluctuations in ambient temperature) can produce artifacts on the thermograms. However, this complexity can be solved by working with thermal imagers of experienced employees.Тепловизионная диагностика (теплография) — это высокоточный метод, позволяющий выявить патологический процесс на доклинической стадии посредством инфракрасного излучения. Для челюстно-лицевой области данный метод может являться одним из методов выбора дополнительной диагностики пациента. Теплография обладает большим количеством положительных характеристик: безопасность проведения манипуляции для пациента и врача; высокая достоверность (до 80%); быстрота и простота исследования; возможность в рамках одного приема обследовать всю челюстно-лицевую область; возможность динамического наблюдения; небольшая стоимость исследования. Сложность использования данного метода заключается лишь в интерпретации результатов, поскольку внешние факторы (поверхностно расположенные сосуды, возраст пациента, толщина подкожно-жировой клетчатки, колебания температуры окружающей среды) могут давать артефакты на теплограммах. Однако данная сложность может быть решена путем работы с тепловизорами опытных сотрудников

Categories of Chinese characters in grammatologocal theory of I. M. Oshanin

The text of I. M. Oshanin’s dissertation “Origin, development and structure of modern Chinese writing” is analyzed. The authors focus on the scientist’s grammatical views on the categorization of Chinese characters. It is noted that Oshanin considered the most successful system of classification of Chinese characters to be a graphophonetic system, showing its effectiveness on numerous examples. The authors believe that Oshanin’s views on the development and structure of the modern Chinese language remain important today.Анализируется текст диссертации И. М. Ошанина «Происхождение, развитие и структура современного китайского письма». Авторы сосредоточивают внимание на грамматологических воззрениях ученого на категоризацию китайских письменных знаков. Отмечено, что наиболее удачной системой классификации китайских иероглифов Ошанин считал графофонетическую, показывая ее эффективность на многочисленных примерах. Авторы считают, что воззрения Ошанина на характер развития и структуры современного китайского языка сохраняют свою значимость и сегодня

Cutaneous lupus erythematosus after treatment with paclitaxel and bevacizumab for metastatic breast cancer: a case report

Abstract Introduction The monoclonal anti-vascular endothelial growth factor antibody bevacizumab is increasingly used in the treatment of several malignant tumors. The usual side effects of this drug are hypertension and proteinuria. Paclitaxel is widely used in the treatment of breast cancer and head and neck carcinomas. Neither of these two drugs typically causes skin disorders. Paclitaxel-related cutaneous lupus erythematosus has been described before, but in earlier cases patients had a history of autoimmune disease. Case presentation We report a case of a 65-year-old Caucasian woman who presented with cutaneous lupus erythematosus after receiving paclitaxel-bevacizumab combination treatment as first-line therapy for metastatic breast cancer. Her cutaneous symptoms and increased serum anti-SSA and anti-SSB antibodies disappeared shortly after the discontinuation of therapy. Conclusion We conclude that cutaneous lupus erythematosus can also be seen in patients without earlier anamnesis of autoimmune disorders and that, furthermore, bevacizumab might cause atypical cutaneous side effects.</p