scholarly journals Biomechanical Constitutive Modeling of the Gastrointestinal Tissues: Where Are We?

2021 ◽  
Author(s):  
Bhavesh Patel ◽  
Alessio Gizzi ◽  
Javad Hashemi ◽  
Yousif Awakeem ◽  
Hans Gregersen ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Constitutive Models ◽  
Strain Energy Function ◽  
Biomechanical Model ◽  
The Body ◽  
Mathematical Representation ◽  
Gi Tract ◽  
Actual Structure ◽  
Pathological Conditions ◽  
Mechanical Models

The gastrointestinal (GI) tract is a continuous channel through the body that consists of the esophagus, the stomach, the small intestine, the large intestine, and the rectum. Its primary functions are to move the intake of food for digestion before storing and ultimately expulsion of feces from the rectum through the anal sphincter. The mechanical behavior of GI tissues thus plays a crucial role for GI function in health and disease. The mechanical properties are typically characterized by a constitutive biomechanical model, which is a mathematical representation of the relation between load and deformation in a tissue. Hence, validated biomechanical constitutive models are essential to characterize and simulate the mechanical behavior of the GI tract under physiological and pathological conditions. Numerous constitutive models have consequently been proposed over the past three decades, mainly inspired by work done in cardiovascular tissues. Here, a comprehensive review of these constitutive models is provided. This review is limited to studies where a model of the strain energy function is proposed to characterize the stress-strain relation of a GI tissue. Several needs are identified for more advanced modeling of GI biomechanics including: 1) Microstructural models that provide actual structure-function relations; 2) Validation of coupled electro-mechanical models accounting for active muscle contractions; 3) Human data under physiological and pathological conditions to develop and validate models. The findings from this review provide guidelines for using existing constitutive models as well as perspective and directions for future studies aimed at establishing new constitutive models for GI tissues.

Healthy Gut, Healthy Brain: The Gut Microbiome in Neurodegenerative Disorders

2020 ◽  
Vol 20 (13) ◽  
pp. 1142-1153 ◽  
Author(s):  
Sreyashi Chandra ◽  
Md. Tanjim Alam ◽  
Jhilik Dey ◽  
Baby C. Pulikkaparambil Sasidharan ◽  
Upasana Ray ◽  
...  
Keyword(s):  
Gut Microbiota ◽  
Neurodegenerative Disorders ◽  
The Body ◽  
Therapeutic Approaches ◽  
Cns Disorders ◽  
Physiological Conditions ◽  
Pathological Conditions ◽  
The Central Nervous System ◽  
Present Understanding ◽  
Lateral Sclerosis

Background: The central nervous system (CNS) known to regulate the physiological conditions of human body, also itself gets dynamically regulated by both the physiological as well as pathological conditions of the body. These conditions get changed quite often, and often involve changes introduced into the gut microbiota which, as studies are revealing, directly modulate the CNS via a crosstalk. This cross-talk between the gut microbiota and CNS, i.e., the gut-brain axis (GBA), plays a major role in the pathogenesis of many neurodegenerative disorders such as Parkinson’s disease (PD), Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS) and Huntington’s disease (HD). Objective: We aim to discuss how gut microbiota, through GBA, regulate neurodegenerative disorders such as PD, AD, ALS, MS and HD. Methods: In this review, we have discussed the present understanding of the role played by the gut microbiota in neurodegenerative disorders and emphasized the probable therapeutic approaches being explored to treat them. Results: In the first part, we introduce the GBA and its relevance, followed by the changes occurring in the GBA during neurodegenerative disorders and then further discuss its role in the pathogenesis of these diseases. Finally, we discuss its applications in possible therapeutics of these diseases and the current research improvements being made to better investigate this interaction. Conclusion: We concluded that alterations in the intestinal microbiota modulate various activities that could potentially lead to CNS disorders through interactions via the GBA.

scholarly journals Selective stimulation of the ferret abdominal vagus nerve with multi-contact nerve cuff electrodes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jonathan A. Shulgach ◽  
Dylan W. Beam ◽  
Ameya C. Nanivadekar ◽  
Derek M. Miller ◽  
Stephanie Fulton ◽  
...  
Keyword(s):  
Vagus Nerve ◽  
Nerve Fibers ◽  
The Body ◽  
Evoked Responses ◽  
Gi Tract ◽  
Selective Stimulation ◽  
Nerve Cuff ◽  
Cuff Electrodes ◽  
Nerve Cuff Electrodes ◽  
Stimulation Of

AbstractDysfunction and diseases of the gastrointestinal (GI) tract are a major driver of medical care. The vagus nerve innervates and controls multiple organs of the GI tract and vagus nerve stimulation (VNS) could provide a means for affecting GI function and treating disease. However, the vagus nerve also innervates many other organs throughout the body, and off-target effects of VNS could cause major side effects such as changes in blood pressure. In this study, we aimed to achieve selective stimulation of populations of vagal afferents using a multi-contact cuff electrode wrapped around the abdominal trunks of the vagus nerve. Four-contact nerve cuff electrodes were implanted around the dorsal (N = 3) or ventral (N = 3) abdominal vagus nerve in six ferrets, and the response to stimulation was measured via a 32-channel microelectrode array (MEA) inserted into the left or right nodose ganglion. Selectivity was characterized by the ability to evoke responses in MEA channels through one bipolar pair of cuff contacts but not through the other bipolar pair. We demonstrated that it was possible to selectively activate subpopulations of vagal neurons using abdominal VNS. Additionally, we quantified the conduction velocity of evoked responses to determine what types of nerve fibers (i.e., Aδ vs. C) responded to stimulation. We also quantified the spatial organization of evoked responses in the nodose MEA to determine if there is somatotopic organization of the neurons in that ganglion. Finally, we demonstrated in a separate set of three ferrets that stimulation of the abdominal vagus via a four-contact cuff could selectively alter gastric myoelectric activity, suggesting that abdominal VNS can potentially be used to control GI function.

A NUMERICAL STUDY ON THE HEMODYNAMIC AND SHEAR STRESS OF DOUBLE ANEURYSM THROUGH S-SHAPED VESSEL

2015 ◽  
Vol 27 (04) ◽  
pp. 1550033 ◽  
Author(s):  
Mahdi Halabian ◽  
Alireza Karimi ◽  
Borhan Beigzadeh ◽  
Mahdi Navidbakhsh
Keyword(s):  
Blood Flow ◽  
Mechanical Behavior ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Flow Simulation ◽  
The Body ◽  
Sweep Angle ◽  
Abdominal Aortic ◽  
Hemodynamic Characteristics ◽  
Refined Meshes

Abdominal aortic aneurysm (AAA) is a degenerative disease defined as the abnormal ballooning of the abdominal aorta (AA) wall which is usually caused by atherosclerosis. The aneurysm grows larger and eventually ruptures if it is not diagnosed and treated. Aneurysms occur mostly in the aorta, the main artery of the chest and abdomen. The aorta carries blood flow from the heart to all parts of the body, including the vital organs, the legs, and feet. The objective of the present study is to investigate the combined effects of aneurysm and curvature on flow characteristics in S-shaped bends with sweep angle of 90° at Reynolds number of 900. The fluid mechanics of blood flow in a curved artery with abnormal aortic is studied through a mathematical analysis and employing Cosmos flow simulation. Blood is modeled as an incompressible non-Newtonian fluid and the flow is assumed to be steady and laminar. Hemodynamic characteristics are analyzed. Grid independence is tested on three successively refined meshes. It is observed that the abrupt expansion induced by AAA results in an immensely disturbed regime. The results may have implications not only for understanding the mechanical behavior of the blood flow inside an aneurysm artery but also for investigating the mechanical behavior of the blood flow in different arterial diseases, such as atherosclerosis.

scholarly journals A Two Joint Neck Model to Identify Malposition of the Head Relative to the Thorax

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3297
Author(s):  
Philipp M. Schmid ◽  
Christoph M. Bauer ◽  
Markus J. Ernst ◽  
Bettina Sommer ◽  
Lars Lünenburger ◽  
...  
Keyword(s):  
Neck Pain ◽  
Body Height ◽  
Biomechanical Model ◽  
The Body ◽  
Head Orientation ◽  
Neck Length ◽  
Proposed Model ◽  
Biofeedback System ◽  
Simple Measurement ◽  
The Impact

Neck pain is a frequent health complaint. Prolonged protracted malpositions of the head are associated with neck pain and headaches and could be prevented using biofeedback systems. A practical biofeedback system to detect malpositions should be realized with a simple measurement setup. To achieve this, a simple biomechanical model representing head orientation and translation relative to the thorax is introduced. To identify the parameters of this model, anthropometric data were acquired from eight healthy volunteers. In this work we determine (i) the accuracy of the proposed model when the neck length is known, (ii) the dependency of the neck length on the body height, and (iii) the impact of a wrong neck length on the models accuracy. The resulting model is able to describe the motion of the head with a maximum uncertainty of 5 mm only. To achieve this high accuracy the effective neck length must be known a priory. If however, this parameter is assumed to be a linear function of the palpable neck length, the measurement error increases. Still, the resulting accuracy can be sufficient to identify and monitor a protracted malposition of the head relative to the thorax.

In-depth gaze at the astonishing mechanical behavior of bone: A review for designing bio-inspired hierarchical metamaterials

2020 ◽  
pp. 108128652097851
Author(s):  
Ivan Giorgio ◽  
Mario Spagnuolo ◽  
Ugo Andreaus ◽  
Daria Scerrato ◽  
Alberto Maria Bersani
Keyword(s):  
Structural Optimization ◽  
Mechanical Behavior ◽  
Bone Tissue ◽  
Hierarchical Structure ◽  
Reconstructive Surgery ◽  
Review Paper ◽  
Tissue Mechanics ◽  
The Hierarchical Structure ◽  
Mechanical Models ◽  
Different Levels

In this review paper, some relevant models, algorithms, and approaches conceived to describe the bone tissue mechanics and the remodeling process are showcased. Specifically, we briefly describe the hierarchical structure of the bone at different levels and underline the geometrical substructure characterizing the bone itself. The mechanical models adopted to describe the bone tissue at different levels of observation are introduced in their essential aspects. Furthermore, the modeling of the evolution, including the growth and resorption of bone, is treated by analyzing the main approaches employed, namely the mechanical feedback concept and the structural optimization perspective. In this regard, the most prominent ways to model the biomechanical stimulus are summarized. The modeling of the interaction with prostheses or grafts commonly used in reconstructive surgery is also recalled. The main aim of this survey consists thereby in providing the appropriate knowledge to mimic the deeply structured hierarchy of the bone tissue for synthesizing innovative and highly performing bio-inspired metamaterials.

Extase scopique, sédimentation langagičre et inscription corporelle. Les images dans la civilisation contemporaine

PARADIGMI ◽  
2009 ◽  
pp. 71-83
Author(s):  
Jean-Jacques Wunenburger
Keyword(s):  
Key Words ◽  
The Body ◽  
Pathological Conditions ◽  
Image Informatics

- Linguistic Sedimentation, and Bodily Inscription At present, we are exposed to an excessive offer of images, which raises a problem of assimilation. Subjects are increasingly passive, in ways that can border on pathological conditions. Yet, it is not so much a question of condemning this situation as of finding a way of re-symbolizing images, saving them from mere contemplation and inserting them in a process of contextualisation. Such a process requires an understanding of the role of the body and of the incorporation of images along the lines of Bachelard's intuition of the "resisting" nature of images. This raises the possibility of an education to images suited to the present age.Key words: Alienation, Education, Embodiment, Image, Informatics, Symbolisation.Parole chiave: Alienazione, Educazione, Immagine, Incorporazione, Informatica, Simbolizzazione.

Some aspects of hemostasis in the tactics of the ophthalmologist. Literature review

2021 ◽  
pp. 265-270
Author(s):  
O.M. Stanishevskaya ◽  
◽  
M.A. Safronova ◽  
G.V. Bratko ◽  
I.Y. Efremova ◽  
...  
Keyword(s):  
Open Angle Glaucoma ◽  
Vascular Diseases ◽  
Laboratory Diagnosis ◽  
The Body ◽  
Vascular Pathology ◽  
Treatment Result ◽  
Important Place ◽  
Correct Orientation ◽  
Pathological Conditions ◽  
Wide Range

Disorders of hemostasis occupy an important place in the structure of vascular diseases and are one of the most frequent pathological conditions encountered in practical medicine. The hemostasis system is naturally the most vulnerable system of the body. Violations of its balance are found in a wide variety of physiological and pathological conditions of the body. It is not uncommon for the first debut of decompensation to lead to an ophthalmologist. In the practice of an ophthalmologist, there are diseases when it is necessary to pay close attention to thrombophilic conditions. Changes in the hemostatic system, affect a wide range of vascular diseases of the eyeball. Recognition of the type of thrombophilia and its timely laboratory diagnosis in patients with vascular diseases of the retina and optic nerve are important in achieving the best treatment results. Multidisciplinary approach to the treatment of vascular diseases of the eyeball and modern diagnostics, including the study of hemostasis, is necessary and relevant to achieve the best clinical and functional treatment result. Timely and correct orientation of patients in vascular pathology is extremely important due to the fact that concomitant systemic pathology can aggravate the course of the disease, therefore, the choice of treatment tactics for this category of patients should be carried out in conjunction with a therapist, cardiologist, hematologist and endocrinologist. Key words: hemostasis, thrombosis CVS, diabet, primary open-angle glaucoma thrombodynamica, cardiovascular pathology.

scholarly journals A Review on Mechanical Models for Cellular Media: Investigation on Material Characterization and Numerical Simulation

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3283
Author(s):  
Guoqiang Luo ◽  
Yuxuan Zhu ◽  
Ruizhi Zhang ◽  
Peng Cao ◽  
Qiwen Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Impact Resistance ◽  
Constitutive Models ◽  
Economic Loss ◽  
Constitutive Relationship ◽  
Cell Models ◽  
Mechanical Models ◽  
Mechanical Properties Characterization ◽  
Buffer Structure

Cellular media materials are used for automobiles, aircrafts, energy-efficient buildings, transportation, and other fields due to their light weight, designability, and good impact resistance. To devise a buffer structure reasonably and avoid resource and economic loss, it is necessary to completely comprehend the constitutive relationship of the buffer structure. This paper introduces the progress on research of the mechanical properties characterization, constitutive equations, and numerical simulation of porous structures. Currently, various methods can be used to construct cellular media mechanical models including simplified phenomenological constitutive models, homogenization algorithm models, single cell models, and multi-cell models. This paper reviews current key mechanical models for cellular media, attempting to track their evolution from their inception to their latest development. These models are categorized in terms of their mechanical modeling methods. This paper focuses on the importance of constitutive relationships and microstructure models in studying mechanical properties and optimizing structural design. The key issues concerning this topic and future directions for research are also discussed.

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