Microtubules Increase Diastolic Stiffness in Failing Human Cardiomyocytes and Myocardium.

BACKGROUND: Diastolic dysfunction is a prevalent and therapeutically intractable feature of heart failure (HF). Increasing ventricular compliance can improve diastolic performance, but the viscoelastic forces that resist diastolic filling and become elevated in human HF are poorly defined. Having recently identified posttranslationally detyrosinated microtubules as a source of viscoelasticity in cardiomyocytes, we sought to test whether microtubules contribute meaningful viscoelastic resistance to diastolic stretch in human myocardium. METHODS: Experiments were conducted in isolated human cardiomyocytes and trabeculae. First, slow and rapid (diastolic) stretch was applied to intact cardiomyocytes from nonfailing and HF hearts and viscoelasticity was characterized after interventions targeting microtubules. Next, intact left ventricular trabeculae from HF patient hearts were incubated with colchicine or vehicle and subject to pre- and posttreatment mechanical testing, which consisted of a staircase protocol and rapid stretches from slack length to increasing strains. RESULTS: Viscoelasticity was increased during diastolic stretch of HF cardiomyocytes compared with nonfailing counterparts. Reducing either microtubule density or detyrosination reduced myocyte stiffness, particularly at diastolic strain rates, indicating reduced viscous forces. In myocardial tissue, we found microtubule depolymerization reduced myocardial viscoelasticity, with an effect that decreased with increasing strain. Colchicine reduced viscoelasticity at strains below, but not above, 15%, with a 2-fold reduction in energy dissipation upon microtubule depolymerization. Post hoc subgroup analysis revealed that myocardium from patients with HF with reduced ejection fraction were more fibrotic and elastic than myocardium from patients with HF with preserved ejection fraction, which were relatively more viscous. Colchicine reduced viscoelasticity in both HF with preserved ejection fraction and HF with reduced ejection fraction myocardium. CONCLUSIONS: Failing cardiomyocytes exhibit elevated viscosity and reducing microtubule density or detyrosination lowers viscoelastic resistance to diastolic stretch in human myocytes and myocardium. In failing myocardium, microtubules elevate stiffness over the typical working range of strains and strain rates, but exhibited diminishing effects with increasing length, consistent with an increasing contribution of the extracellular matrix or myofilament proteins at larger excursions. These studies indicate that a stabilized microtubule network provides a viscous impediment to diastolic stretch, particularly in HF.

Viscoelastic Properties of Human Facial Skin and Comparisons with Facial Prosthetic Elastomers.

Prosthesis discomfort and a lack of skin-like quality is a source of patient dissatisfaction with facial prostheses. To engineer skin-like replacements, knowledge of the differences between facial skin properties and those for prosthetic materials is essential. This project measured six viscoelastic properties (percent laxity, stiffness, elastic deformation, creep, absorbed energy, and percent elasticity) at six facial locations with a suction device in a human adult population equally stratified for age, sex, and race. The same properties were measured for eight facial prosthetic elastomers currently available for clinical usage. The results showed that the prosthetic materials were 1.8 to 6.4 times higher in stiffness, 2 to 4 times lower in absorbed energy, and 2.75 to 9 times lower in viscous creep than facial skin (p < 0.001). Clustering analyses determined that facial skin properties fell into three groups-those associated with body of ear, cheek, and remaining locations. This provides baseline information for designing future replacements for missing facial tissues.

A sutureless technique for securing leaking sclerotomies with viscoelastic substances in 23-gauge microincision vitrectomy surgery.

AIM: To introduce and evaluate the clinical efficacy of a new technique, the use of viscoelastic substances (VS) to close leaking sclerotomy in 23G microincision vitrectomy, and to observe its effect on the visual acuity and intraocular pressure (IOP) of patients. METHODS: Patients who underwent 23G vitrectomy in Ningbo Eye Hospital before the use of VS technique (June 2019 to September 2020) and after the use of VS technique (October 2020 to December 2021) were selected as the subjects of this study. The above cases underwent operation by the same surgeon and were retrospectively analyzed. VS technique was used as the alternative to suturing, in which a small amount of VS was injected at the leaking sclerotomy and then gently massaged to confirm leaking sclerotomy closure. RESULTS: A total of 174 eyes were covered in the study, including 84 eyes in the control group (before the use of VS technique) and 90 eyes in the VS technique group. The number of eyes that needed to be sutured decreased considerably from 42.9% in the control group to 3.3% in the VS technique group, and the proportion of subconjunctival hemorrhage at 1-2d after surgery decreased remarkably from 35.7% in the control group to 2.2% in the VS technique group. No substantial differences in the incidence of mean IOP and low IOP were found between 1-2 and 3-20d after surgery in the VS technique group. No major complications associated with VS technique were identified during the study. CONCLUSION: In 23G microincision vitrectomy, VS technique is a safe, simple, and effective method to close leaking sclerotomy.

A primer on ocular viscosurgical devices.

PURPOSE: To provide pharmacists with an overview of ocular viscosurgical devices (OVDs) and a comprehensive resource describing characteristics of commercially available agents. SUMMARY: OVDs are substances that are injected into the eye during ophthalmic procedures, such as cataract surgery, to reduce injury to the endothelium that may result from surgical manipulation. Currently available OVDs are composed of one or more of the following active ingredients: sodium hyaluronate, sodium chondroitin sulfate, and hydroxypropylmethylcellulose. Rheologic properties of OVDs, such as viscosity, elasticity, pseudoplasticity, and cohesion, affect the products' function and performance. Based on rheologic properties, OVDs can be generally classified as cohesive or dispersive. Given each products' unique characteristics, OVDs are not interchangeable. An understanding of OVD characteristics and role in practice allows for improved product selection, which varies based on patient characteristics and procedure. Availability of OVD information and literature is generally lacking since OVDs are regulated by the US Food and Drug Administration (FDA) as medical devices. This primer includes an overview of relevant ophthalmic surgical practices and the landscape of comparative efficacy and safety literature to assist in formulary decision-making. This review also provides a comprehensive guide to commercially available OVDs and a discussion on practical considerations for the pharmacist. CONCLUSION: Pharmacists may be tasked with handling OVDs in institutional settings. Knowledge about OVD rheologic properties, product characteristics, role in practice, and available literature is necessary for managing formularies and ensuring optimal product selection.

Thermal behavior and viscoelastic properties of gutta-percha used for back-filling the root canal.

BACKGROUND/PURPOSE: In clinical operations, qualitative differences in the texture and operational feeling of the regular type and soft type back-filled gutta-percha are readily discernible. This study aimed to investigate and compare the thermal behavior and physical properties of the two gutta-percha materials. MATERIALS AND METHODS: The chemical compositions of regular and soft type Gutta-Percha Obturator® pellets were examined via energy dispersive X-ray spectroscopy. The thermal behaviors of the pellets during heating and cooling were evaluated using a differential scanning calorimeter. Finally, the viscoelastic properties of the two materials during cooling were assessed using a modular compact rheometer. RESULTS: The soft type gutta-percha contained a greater atomic percentage of zinc than the regular type material. In addition, the soft type gutta-percha exhibited exothermic peaks during cooling, whereas the regular type gutta-percha did not. The two materials exhibited different viscoelastic behaviors under cooling. In particular, the rate of change of the loss factor for the soft type gutta-percha was more than that of the regular type gutta-percha at temperature lower than 80°C. CONCLUSION: The soft type gutta-percha underwent significant crystallization during cooling, and therefore exhibited pronounced volume shrinkage. Furthermore, the soft type gutta-percha underwent a greater rate of change in viscoelasticity under cooling than the regular type gutta-percha, and exhibited poorer physical stability. Consequently, in the back-packing procedure, soft type gutta-percha must be compacted more often over time than regular type gutta-percha to ensure the same quality of root canal obturation.

Monitorização da coagulação sanguínea perioperatória / Perioperative blood coagulation monitoring

A monitorização perioperatória da coagulação sanguínea é crítica para entender melhor as causas de hemorragia, guiar terapias hemostáticas e prever o risco de sangramento durante procedimento cirúrgico. Nosso entendimento de coagulopatia perioperatória, ferramentas diagnósticas e abordagens terapêuticas têm evoluído nos últimos anos. O recentementedesenvolvido modelo celular da coagulação somado aos novos testes hemostáticos viscoelásticos (TEG e ROTEM) e testes de função plaquetária realizados à beira do leito facilita o entendimento e mede a formação e resolução do coágulo no sangue total, possibilitando rápido diagnóstico e tratamento da coagulopatia perioperatória.

The perioperative blood coagulation monitoring is critical to better understand the causes of bleeding, guide hemostatic therapies, and predict the risk of bleeding during surgery. Our understandings of perioperative coagulopathy, diagnostic tools, and therapeutic approaches have evolved in recent years. The newly developed cell coagulation model combined with new hemostatic viscoelastic tests (TEG or ROTEM) and platelet function tests, carried out by the bedside, facilitates the understanding and measure of the formation and resolution of the clot in whole blood, enabling rapid diagnosis and treatment of perioperative coagulopathy.

A major problem in strabismus and its possible solution / Um grande problema no estrabismo e suas possíveis soluções

Purpose: One of the challenges in strabismus is to guarantee stability of the surgical corrections. Re-surgeries are often required even after careful diagnosis, planning, and execution. Several factors contribute to this undesired outcome and the existing management strategies are ineffective. The present alternative is to compensate for their consequences. Ocular rotations are evoked by muscular contractions and relaxations (active forces). During eye movement, periocular tissues are stretched, storing part of the kinetic energy, which may be posteriorly recovered (passive forces), whereas the remaining part of the energy is lost via friction and inelastic deformations (dissipative forces). A method for measuring the forces that cause post-surgery eye drift has not been reported. However, this may be indirectly determined as a function of the respective mechanical variables. The estimated ratio between the kinetic energies of a post-surgery eye drift and a normal pursuit eye movement is ~10-15. Theoretically, it can be expected that the addition of continuously acting forces of such magnitudes to the oculomotor system might prevent the undesired post-surgery eye movement. Methods: Several methods for increasing the restraining, dissipative forces to ocular rotations may be conceived. One method is to increase the friction to ocular movements, as for instance, by periocular injection of viscous substances. Another possibility is to use the forces of a magnetic field, which may stabilize the eye in a desired position without avoiding the rotations caused by greater muscular forces acting on it. It has been demonstrated that these forces neutralize the nystagmic movements, whose intensities of mechanical variables are much higher than those of a post-surgery eye drift. Some models of application of this technique are then discussed. Small magnets fixed to the orbit and metallic ferromagnetic elements fixed to the sclera to cover a suitable ...

Objetivo: Um grande problema nos estrabismos é garantir um resultado bom e estável de suas correções cirúrgicas. A necessidade de reoperações é relativamente alta, apesar de cuidadosos procedimentos diagnósticos, planejamento cirúrgico e execução tenham sido tomados. O resultado indesejado é devido a muitos fatores que ainda não são apropriadamente controlados. A alternativa atual é, então, compensar as consequências correspondentes. Rotações oculares são evocadas por contrações e relaxamentos musculares (forças ativas). Nesses movimentos oculares, tecidos perioculares são distendidos, mantendo parte da energia cinética, que pode ser posteriormente recuperada (forças passivas), enquanto outra parte é definitivamente perdida em fricção e deformações inelásticas (forças dissipativas). Não é conhecida a medida das forças que causam um desvio ocular pós-operatório, mas ela pode ser indiretamente determinada como função das respectivas variáveis mecânicas. A relação entre as energias cinéticas de um desvio ocular pós-operatório e de um movimento ocular persecutório normal pode ser então estimada como de cerca 10-15. Teoricamente, pode-se esperar que a adição de forças dessas magnitudes ao sistema oculomotor, continuadamente atuantes, possam prevenir os movimentos pós-operatórios indesejados. Métodos: Podem ser concebidas várias possibilidades de aumento das forças dissipativas, restritivas de rotações oculares. Uma é a de aumentar a fricção aos movimentos oculares como, por exemplo, por injeções perioculares de substâncias viscoelásticas. Outra possibilidade é oferecida por forças de campos magnéticos ...

Comparação entre o efeito imediato e agudo de três protocolos de alongamento dos músculos isquiotibiais e paravertebrais / Comparison between the immediate and acute effect of three stretching protocols of hamstrings and paravertebral muscles

JUSTIFICATIVA E OBJETIVOS: Vários estudos apontam que o alongamento muscular aumenta a flexibilidade, mas poucas pesquisas comparam métodos no seu efeito imediato e agudo, principalmente com respeito ao chamado cinesioalongamento. O objetivo deste estudo foi comparar o efeito imediato e agudo de três protocolos de alongamento dos músculos isquiotibiais e paravertebrais, quanto à flexibilidade articular e a extensibilidade muscular. MÉTODO: Utilizou-se 41 voluntários, com extensibilidade de isquiotibiais limitada. Os participantes foram aleatorizados em três grupos: alongamento ativo estático (AE) (n = 14), facilitação neuromuscular proprioceptiva (FNP) (n = 14) e cinesioalongamento (CA) (n = 13). Realizaram-se três avaliações por prancha de goniometria e pelo banco de Wells; a primeira antes do protocolo de alongamento, a segunda imediatamente após e a terceira 24 horas após. Os alongamentos foram realizados em ambos os membros inferiores e sustentados por 32 segundos. Os dados foram analisados pela Análise de Variância, com nível de significância 5%. RESULTADOS: houve diferença significativa entre a primeirae a segunda avaliação para grupos AE e CA na prancha de goniometria. Todos os grupos apresentaram diferença significativa entre a segunda e terceira avaliação. Quando observados os resultados obtidos com a avaliação do banco de Wells, houve diferenças ignificativa em todos os grupos se comparado a primeira avaliação com a segunda. Quando se comparou a segunda e terceira avaliação, os grupos AE e FNP apresentaram diferença significativa. Não houve diferença significativa quando comparado os três protocolos de alongamento entre si, nos dois instrumentos. CONCLUSÃO: O efeito imediato do alongamento é o aumento da flexibilidade articular e da extensibilidade muscular. Já o efeito agudo mostrou que há uma perda dos ganhos obtidos, não sendos ignificativa no grupo CA.

BACKGROUND AND OBJECTIVES: Several studies show that muscle stretching increases flexibility, but little research comparing methods in your immediate and acute, especially with respect to the call kinesiostretching. To evaluate and compare acute and immediate effects of three protocols for stretching hamstrings and paravertebral muscles, as the joint flexibility and muscle extensibility. METHOD: We used 41 volunteers, with hamstrings limited extensibility.The participants were randomized into three groups:active static stretching - AS (n = 14), proprioceptive neuromuscularfacilitation - PNF (n = 14) and kinesiostretching - KS (n= 13). In total, three assessments by goniometry board and Wells bench, the first before the stretching protocol, immediately after the second and third after 24 hours. The stretches were performed in both legs and sustained for 32 seconds. The data were analyzed by ANOVA with significance level of 5%. RESULTS: The goniometry evaluation board there was significant difference between the first and second assessment for groups AE and KS. All groups showed significant difference between the second and third assessment. When observing results of the evaluation of the Wells bench was significant in all groups when compared to the first evaluation with the second. When comparingthe second and third assessment, the groups AE and PNF showed significant difference. There was no significant difference when comparing each stretching protocols among them selves. CONCLUSION: The immediate effect of stretching is to increase joint flexibility and extensibility of muscle. Since the acute effect showed that there are a loss of gain obtained, not beingsignificant in the KS.

Uso de viscoelásticos na facoemulsificação em cães portadores de catarata: efeitos sobre a pressão intraocular, a morfologia das células endoteliais e a espessura corneana / Use of viscoelastic substances for the phacoemulsification in dogs with cataract: effects on the intraocular pressure, morphology of endothelial cells, and corneal thickness

Avaliaram-se as células endoteliais, a espessura corneana e a pressão intraocular (PIO) de cães portadores de catarata madura, empregando-se viscoelástico à base de hialuronato de sódio 3 por cento e sulfato de condroitina 4 por cento e hidroxipropilmetilcelulose 2 por cento, utilizando-se 20 cães, distribuídos entre os dois grupos dos viscoelásticos. A técnica cirúrgica adotada foi a da facoemulsificação bimanual. As avaliações tonométricas foram efetuadas antes e após o ato cirúrgico, aos 1, 7, 14, 21, 28 e 60 dias de pós-operatório, e a microscopia especular, antes e após 7, 28 e 60 dias. Não houve diferença estatística entre os grupos quanto à PIO, com exceção aos 14 dias, em que se observou maior PIO com o uso de hialuronato de sódio 3 por cento e sulfato de condroitina 4 por cento. Não houve diferença entre os grupos quanto aos parâmetros relacionados ao endotélio, com diminuição discreta da densidade celular endotelial e aumento da área celular com a utilização de hidroxipropilmetilcelulose 2 por cento. A utilização de ambos os dispositivos viscoelásticos analisados é recomendada para o procedimento de facoemulsificação em cães.

The endothelial cells, the corneal thickness, and the intraocular pressure (IOP) were evaluated in dogs with cataract, using viscoelastic substances based on 3 percent sodium hyaluronate and 4 percent chondroitin sulfate and comparing them with 2 percent hydroxypropylmethylcellulose. Twenty dogs were distributed in two groups of ten, each using one viscoelastic material. The surgical technique was bimanual phacoemulsification. The tonometric evaluations were made before and at one, seven, 14, 21, 28, and 60 days after the surgery and the specular microscopy before and after seven, 28, and 60 days. No statistical difference between groups was found according to IOP, except at 14 days, which was significantly higher with the use of 3 percent sodium hyaluronate and 4 percent chondroitin sulfate. There was no statistical difference between the groups considering the parameters related to the endothelium, with slight decrease in endothelial cell density and increase of cell area with the use of 2 percent hydroxypropylmethylcellulose. The use of both viscoelastic devices is recommended for the phacoemulsification in dogs.