USSR Space Life Sciences Digest, issue 6

This is the sixth issue of NASA's USSR Space Life Sciences Digest. It contains abstracts of 54 papers recently published in Russian language periodicals and bound collections and of 10 new Soviet monographs. Selected abstracts are illustrated with figures and tables from the original. Additional features include a table of Soviet EVAs and information about English translations of Soviet materials available to readers. The topics covered in this issue have been identified as relevant to 26 areas of aerospace medicine and space biology. These areas are adaptation, biospherics, body fluids, botany, cardiovascular and respiratory systems, developmental biology, endocrinology, enzymology, exobiology, genetics, habitability and environment effects, health and medical treatment, hematology, human performance, immunology, life support systems, mathematical modeling, metabolism., microbiology, morphology and cytology, musculoskeletal system, neurophysiology, nutrition, perception, personnel selection, psychology, radiobiology, reproductive biology, and space medicine

Structure-property relations in porcine brain tissue: strain rate and stress-state dependence

Due to traumatic brain injury (TBI), numerous studies have focused on comprehensively determining the mechanical properties of the brain. This study examined the strain rate dependence of porcine brain under compression, and the microstructural damage was quantified using a confocal microscope and graphical user interface (GUI). The selected strain rates were 0.10 s-1, 0.025 s-1, and 0.00625 s-1 while the strain levels targeted for confocal imaging were 15%, 30%, and 40%. This study also characterized the stress-state dependence at a strain rate and strain level of 0.10 s-1 and 40%, respectively, under compression, tension, and shear. Strain rate dependency data exhibited viscoelastic behavior, and the analysis parameters correlated with increasing strain rate and strain level. Stress-state dependency data demonstrated distinct nonlinear behavior, and disparities were observed in the analysis parameters between different testing modes. Finite element procedures can implement this supplementary data for devising more realistic models

Characterization of biaxial mechanical properties of rubber and skin

textBreast cancer is one of the most frequently diagnosed cancers affecting women in the United States. An ongoing objective of many research groups is to develop a biomechanical breast model for different applications, ranging from surgical outcome predictions for patients undergoing breast reconstruction surgery, to image registration for planning plastic surgery. Achieving the goal of developing a physics based biomechanical model of the human breast requires the determination of material properties of the various tissues constituting the breast. The objective of this thesis is to develop an appropriate hybrid experimental-numerical technique to enable the calibration of material parameters of skin for different constitutive models (commonly used for skin). The quantification of the material parameters thus obtained validates the bulge test method to be used in testing soft tissue specimens like skin. A bulge test device was custom-built for this work; it consists of a pressure chamber, two digital cameras, and a syringe pump as its main components. The syringe pump provides a constant flow rate of water into the pressure chamber and results in the bulging of specimens with a diameter between 45 mm and 80 mm. Three-dimensional Digital Image Correlation technique is used to obtain full field displacement measurements of the three dimensional shape of the bulge. Tests were performed on commercial rubber sheets of different thickness and on porcine skin specimens; in these tests, the bulge shape was measured at monotonically increasing and decreasing pressure levels, as well as during cyclic loading allowing determination of the deformation and strain fields over the specimen surface. In order to extract the material properties, a hybrid experimental-numerical method was used: the experiment was modeled numerically using the finite element analysis software Abaqus, imposing the commonly used Mooney-Rivlin model for isotropic materials and the Gasser-Ogden-Holzapfel model for anisotropic materials. A comparison between the experimentally measured and numerically simulated bulge shapes was used to determine the optimized material parameters under biaxial loading conditions over a large range of stretch levels.Biomedical Engineerin

The Role of the Nucleus Pulposus in Human Intervertebral Disc Mechanical Function Quantified by Mechanical Loading and Non-Invasive Imaging

The intervertebral disc performs the mechanical roles of supporting loads, permitting motion, and dissipating energy. Disc degeneration affects a large portion of the population, reduces the jointâ??s effectiveness, and is strongly implicated as a cause of low back pain. Degeneration is an irreversible process that manifests early within the centralized nucleus pulposus and subsequently affects other disc components. An incomplete understanding of the role of the nucleus pulposus and how alterations in nucleus function affect disc mechanics has hindered successful development of disc degeneration treatment. The objective of this dissertation was to evaluate the mechanical contributions of the nucleus pulposus to intervertebral disc function in compressive loading. In cyclic loading experiments, it was determined that removal of the nucleus pulposus via nucleotomy caused acute changes to the discâ??s mechanical response such as a decrease in compressive stiffness with an accompanying increase in compressive strain. These changes correspond to hypermobility, which alters overall spinal mechanics and may impact low back pain via altered motion throughout the spinal column. In addition to these acute changes, nucleotomy also decreased the fluid-flow related effects of cyclic compressive loading. Filing the void left by nucleotomy with a hydrogel implant preserved the creep response of the discs. A procedure for creating disc strain templates, which describe average disc strain, from MR images taken before and after loading was developed to non-invasively measure internal disc strains that result from compression loading. In mildly-degenerate human discs, removal of the nucleus increased axial strain throughout the annulus fibrosus, consistent with the existing literature stating that the nucleus plays a significant role in supporting compressive loads. Removal of the nucleus also unevenly altered the distribution of circumferential and radial strains within the annulus. Nucleotomy caused substantially higher circumferential strain in the posterolateral region, which may increase the risk of annular tears. The novel tools developed in this work and the experimental results can be utilized to further understand the mechanical role of the nucleus pulposus on intervertebral disc function, how that role changes with degeneration, and to design and treatments that restore disc mechanics

Characterization of a Multi-Laminate Angle-Ply AF Patch for Annulus Fibrosus Repair

Annually, over 5.7 million Americans are diagnosed with two IVD-associated pathologies: IVD herniation (IVDH- a mechanical disruption of the concentric fibrous layers of the annulus fibrosus (AF))) and degeneration (IVDD- a multifactorial process which initiates within the inner gelatinous core (NP), and results in a biochemical degradation of NP tissue), with over 2.7 million requiring surgical inteventions.1,2 Although both underlying pathologies are different, quite often they both lead to a decrease in IVD height, impaired mechanical function, and increased pain and disability. These pain symptoms affect approximately 80% of the adult population during their lifetime with estimated expenditures exceeding $85.9 billion.3,4 Current surgical procedures for IVDH and IVDD are palliative and suffer from drawbacks. While they are performed to address patient symptoms, they fail to address the underlying pathology of a defect remaining within the subsequent layers of the AF. An effective AF closure/repair device in conjunction with a less aggressive discectomy for IVDH and/or NP arthroplasty for IVDD, may result in improved patient outcomes, decreased pain, and provide fewer revision surgeries via lower re-herniation and expulsion rates.5,6 Therefore, an intact AF must be re-established to prevent implant expulsion or re-herniation, thus addressing the two major spinal pathologies directly associated with an IVD. Currently within the medical device market, no tissue engineering biomaterials are available for AF closure/repair. Current market AF closure devices (Intrinsic Barricaid, Anulex X-Close Tissue Repair System, and Anulex Inclose Surgical Mesh System) are synthetic materials focused solely on preserving and reinforcing the native tissue and lack efficient strategies for implantation, fixation, and regeneration. Therefore, there has been an increase in tissue engineering and regenerative therapeutic approaches aiming for structural and biological AF repair investigated over the last decade using in vivo and in vitro experimentation. It is proposed that the optimum AF tissue engineering scaffold should reproduce the architecture, and the mechanical properties of the native human AF tissue.7 Recent articles illustrate several novel suture, seal, and barrier techniques currently under development, resulting in an increasing attention at scientific workshops and conferences.8-15 To develop a tissue engineering biomaterial that is suitable for AF closure it must meet the following criteria: (1) mimic the structural angle-ply architecture of the native AF, (2) withstand static and dynamic mechanical properties mimicking the native functional characteristics, and (3) express cytocompatibility while promoting tissue regeneration. Current biomaterials growing attention in the tissue engineering academic field, electrospinning, polymers, glue, silk scaffolds, and honeycomb-scaffolds, require complex manufacturing procedures and typically work to address two of the three criteria (mimicking the biological and structural characteristics).5 Although the mechanical advantage of closing annular defects to retain NP material seems intuitive, only recently have AF closure devices begun to examined in human cadaveric or animal tissues for their ability to withstand in situ IDP or flexibility testing.16 Therefore, the use of decellularized tissue from a xenogeneic source is ideal due to its advantage of maintaining native extracellular matrix (ECM) while also removing all potential harmful xenogeneic factors. We propose to address all three criteria with the development of a biomimetic angle-ply annulus fibrosus patch comprised of decellularized porcine pericardium. Porcine pericardium was chosen due to its native type I collagen content, mechanical strength, and cytocompatibility. The objectives of this research were to investigate the development of a biomimetic patch, consisting of decellularized porcine pericardium, to biologically augment AF repair by (1) characterizing the micro-architecture of the multi-laminate angle-ply AF patch, (2) evaluating the mechanical properties through static and dynamic tensile loading and impact resistance of IDP, and (3) evaluating the cytocompatibility of the patch using a healthy alternative cell source for AF tissue regeneration

Aerospace Medicine and Biology: A continuing bibliography with indexes, supplement 182, July 1978

This bibliography lists 165 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1978

Shear-promoted drug encapsulation into red blood cells: a CFD model and μ-PIV analysis

The present work focuses on the main parameters that influence shear-promoted encapsulation of drugs into erythrocytes. A CFD model was built to investigate the fluid dynamics of a suspension of particles flowing in a commercial micro channel. Micro Particle Image Velocimetry (μ-PIV) allowed to take into account for the real properties of the red blood cell (RBC), thus having a deeper understanding of the process. Coupling these results with an analytical diffusion model, suitable working conditions were defined for different values of haematocrit

Repair, regenerative and supportive therapies of the annulus fibrosus: achievements and challenges

Lumbar discectomy is a very effective therapy for neurological decompression in patients suffering from sciatica due to hernia nuclei pulposus. However, high recurrence rates and persisting post-operative low back pain in these patients require serious attention. In the past decade, tissue engineering strategies have been developed mainly targeted to the regeneration of the nucleus pulposus (NP) of the intervertebral disc. Accompanying techniques that deal with the damaged annulus fibrous are now increasingly recognised as mandatory in order to prevent re-herniation to increase the potential of NP repair and to confine NP replacement therapies. In the current review, the requirements, achievements and challenges in this quickly emerging field of research are discussed