Results for “Tissue” — Page 10

NASA NTRS2024

Effects of Low Dose Radiation and Radiation Countermeasures on Infection By Spaceflight Analogue Cultured Salmonella Using 3-D Biometric Human Tissue Models

While both microgravity and radiation are major biological stressors associated with the spaceflight environment, their cumulative impact on host-pathogen interactions and infectious disease risks are rarely considered. This is critical to address, since the cumulative effects of these stressors during spaceflight may result in unexpected negative impacts on crew health and performance that neither condition alone would predict, thus limiting the ability to develop effective countermeasures. Previously, we showed that both spaceflight and spaceflight analogue culture increased the virulence and pathogenesis-related characteristics of the foodborne pathogen, Salmonella Typhimurium (S. Typhimurium), which is responsible for disqualification of food destined for the International Space Station and Salmonella spp. have been found aboard NASA spacecraft. Recently, we demonstrated that spaceflight-analogue culture of S. Typhimurium increased its ability to infect 3-D biomimetic human intestinal tissue models. In a separate study, we showed low dose radiation damaged our 3-D intestinal models. The primary objective of this proposal is to evaluate the possibility that low dose radiation will exacerbate the already increased bacterial pathogenicity of S. Typhimurium observed following spaceflight analogue culture. In addition, we will determine the impact of a radiation countermeasure to provide protection against both radiation and pathogen-induced tissue damage and inflammation. Hypothesis: The already enhanced infection potential of spaceflight analogue cultured S. Typhimurium will be further exacerbated when used to infect host cells exposed to low dose radiation and this enhanced pathogenicity can be mitigated by a radioprotective compound. Aims: 1. Characterize the impact of spaceflight-analogue culture on the ability of S. Typhimurium to infect 3-D biomimetic intestinal tissue models before and after exposure to low dose radiation. 2. Evaluate the ability of the radioprotective compound, EC-18, to protect 3-D intestinal models from low dose radiation, S. Typhimurium infection, and the cumulative impact of these stressors. Significance: Current infectious disease risk assessments for spaceflight do not consider the potential for increased susceptibility to infection and disease resulting from exposure to low dose radiation, which is a critical consideration. This study will provide key evidence to determine if exposure to low dose radiation may be a factor in astronaut susceptibility to infection during long duration exploration missions and the impact of selected countermeasures to mitigate that risk to crew health. This study has been initiated and data collection is beginning.

Jennifer Barrila↗

NASA NTRSDate not supplied

Effects of Low Dose Radiation and Radiation Countermeasures on Infection by Spaceflight Analogue Cultured Salmonella Using 3-D Biomimetic Human Tissue Models

While both microgravity and radiation are major biological stressors associated with the spaceflight environment, their cumulative impact on host-pathogen interactions and infectious disease risks are rarely considered. This is critical to address, since the cumulative effects of these stressors during spaceflight may result in unexpected negative impacts on crew health and performance that neither condition alone would predict, thus limiting the ability to develop effective countermeasures. Previously, we showed that both spaceflight and spaceflight analogue culture increased the virulence and pathogenesis-related characteristics of the foodborne pathogen, Salmonella Typhimurium (S. Typhimurium), which is responsible for disqualification of food destined for the International Space Station and Salmonella spp. have been found aboard NASA spacecraft. Recently, we demonstrated that spaceflight-analogue culture of S. Typhimurium increased its ability to infect 3-D biomimetic human intestinal tissue models. In a separate study, we showed low dose radiation damaged our 3-D intestinal models. The primary objective of this proposal is to evaluate the possibility that low dose radiation will exacerbate the already increased bacterial pathogenicity of S. Typhimurium observed following spaceflight analogue culture. In addition, we will determine the impact of a radiation countermeasure to provide protection against both radiation and pathogen-induced tissue damage and inflammation. Hypothesis: The already enhanced infection potential of spaceflight analogue cultured S. Typhimurium will be further exacerbated when used to infect host cells exposed to low dose radiation and this enhanced pathogenicity can be mitigated by a radioprotective compound. Aims: 1. Characterize the impact of spaceflight-analogue culture on the ability of S. Typhimurium to infect 3-D biomimetic intestinal tissue models before and after exposure to low dose radiation. 2. Evaluate the ability of the radioprotective compound, EC-18, to protect 3-D intestinal models from low dose radiation, S. Typhimurium infection, and the cumulative impact of these stressors. Significance: Current infectious disease risk assessments for spaceflight do not consider the potential for increased susceptibility to infection and disease resulting from exposure to low dose radiation, which is a critical consideration. This study will provide key evidence to determine if exposure to low dose radiation may be a factor in astronaut susceptibility to infection during long duration exploration missions and the impact of selected countermeasures to mitigate that risk to crew health. This study has been initiated and data collection is beginning.

Jennifer Barrila↗

NASA NTRS1997

Biomaterials for tissue engineering: summary

This article summarizes presentations and discussion at the workshop "Enabling Biomaterial Technology for Tissue Engineering," which was held during the Fifth World Biomaterials Congress in May 1996. Presentations covered the areas of material substrate architecture, barrier effects, and cellular response, including analysis of biomaterials challenges involved in producing specific tissue-engineered products.

Non-NASA Center↗

NASA NTRS2017

Multi-Layer RF Tissue Phantoms for Mimicking a Human Core

This work presents the design recipe, fabrication process and characterization of tissue-simulating materials, configured as a physical model to mimic the electrical and some physical properties of an abdominal cavity. The complete three-layer design is called the human core model (HCM) see Fig. 1. To our knowledge, presented is the first hybrid skin-muscle phantom developed to mimic the electrical properties of the intervening tissue layers of an abdominal cavity within the frequency band of 1 GHz - 2 GHz, a band of interest for human body sensing due to its deep detection depth.

Biomedical Microwave Sensing↗

NASA NTRS1995

Integrin-extracellular matrix interactions in connective tissue remodeling and osteoblast differentiation

The differentiaton of bone cells is a complex multistep process. Bone is somewhat unusual in that it is very actively and continually remodeled in the adult and that maintenance of its mass in the mature organism is exquisitely sensitive to mechanical as well as chemical signals. Bone is also unique because it consists of a very large amount of extracellular matrix (ECM) that is mineralized. The integrin family of ECM receptors has been shown to play an important role in tissue morphogenesis in several systems. Our studies on the regulation of matrix remodeling enzymes by integrins in rabbit synovial fibroblasts show that two b1 integrin fibronectin (FN) receptor complexes (alpha 5 beta 1 and alpha 4 beta 1) cooperate in detecting subtle changes in the composition of the ECM. As a result of signal transduction by these integrins, the levels of mRNA and protein for several members of the metalloproteinase family are regulated in these cells. We have also used antibody and RGD peptide perturbation studies to determine the significance of cell/ECM interactions to normal osteogenesis. We found that interactions between the cell binding domain of FN and integrins are required for both normal morphogenesis and gene expression in cultured osteoblasts that differentiate to form bone-like tissue in culture. These data lead us to propose that beta 1 integrins play an important role in osteoblast differentiation as well as in bone remodeling.

NASA Discipline Number 26-10↗

NASA NTRS2000

Effects of gene deletion of the tissue inhibitor of the matrix metalloproteinase-type 1 (TIMP-1) on left ventricular geometry and function in mice

Alterations in the expression and activity of the matrix metalloproteinases (MMPs) and the tissue inhibitors of the MMPs (TIMPs) have been implicated in tissue remodeling in a number of disease states. One of the better characterized TIMPs, TIMP-1, has been shown to bind to active MMPs and to regulate the MMP activational process. The goal of this study was to determine whether deletion of the TIMP-1 gene in mice, which in turn would remove TIMP-1 expression in LV myocardium, would produce time-dependent effects on LV geometry and function. Age-matched sibling mice (129Sv) deficient in the TIMP-1 gene (TIMP-1 knock-out (TIMP-1 KO), n=10) and wild-type mice (n=10) underwent comparative echocardiographic studies at 1 and 4 months of age. LV catheterization studies were performed at 4 months and the LV harvested for histomorphometric studies. LV end-diastolic volume and mass increased (18+/-4 and 38+/-3%, respectively, P<0.05) at 4 months in the TIMP-1 KO group; a significant increase compared to wild-type controls (P<0.05). At 4 months, LV and end-diastolic wall stress was increased by over two-fold in the TIMP-1 KO compared to wild type (P<0.05). However, LV systolic pressure and ejection performance were unchanged in the two groups of mice. LV myocyte cross-sectional area was unchanged in the TIMP-1 KO mice compared to controls, but myocardial fibrillar collagen content was reduced. Changes in LV geometry occurred in TIMP-1 deficient mice and these results suggest that constitutive TIMP-1 expression participates in the maintenance of normal LV myocardial structure. Copyright 2000 Academic Press.

Non-NASA Center↗

NASA NTRS1998

Manufacture of porous biodegradable polymer conduits by an extrusion process for guided tissue regeneration

We have fabricated porous, biodegradable tubular conduits for guided tissue regeneration using a combined solvent casting and extrusion technique. The biodegradable polymers used in this study were poly(DL-lactic-co-glycolic acid) (PLGA) and poly(L-lactic acid) (PLLA). A polymer/salt composite was first prepared by a solvent casting process. After drying, the composite was extruded to form a tubular construct. The salt particles in the construct were then leached out leaving a conduit with an open-pore structure. PLGA was studied as a model polymer to analyze the effects of salt weight fraction, salt particle size, and processing temperature on porosity and pore size of the extruded conduits. The porosity and pore size were found to increase with increasing salt weight fraction. Increasing the salt particle size increased the pore diameter but did not affect the porosity. High extrusion temperatures decreased the pore diameter without altering the porosity. Greater decrease in molecular weight was observed for conduits manufactured at higher temperatures. The mechanical properties of both PLGA and PLLA conduits were tested after degradation in vitro for up to 8 weeks. The modulus and failure strength of PLLA conduits were approximately 10 times higher than those of PLGA conduits. Failure strain was similar for both conduits. After degradation for 8 weeks, the molecular weights of the PLGA and PLLA conduits decreased to 38% and 43% of the initial values, respectively. However, both conduits maintained their shape and did not collapse. The PLGA also remained amorphous throughout the time course, while the crystallinity of PLLA increased from 5.2% to 11.5%. The potential of seeding the conduits with cells for transplantation or with biodegradable polymer microparticles for drug delivery was also tested with dyed microspheres. These porous tubular structures hold great promise for the regeneration of tissues which require tubular scaffolds such as peripheral nerve, long bone, intestine, or blood vessel.

NASA Discipline Cell Biology↗

NASA NTRS1998

Bioreactor perfusion system for the long-term maintenance of tissue-engineered skeletal muscle organoids

Three-dimensional skeletal muscle organ-like structures (organoids) formed in tissue culture by fusion of proliferating myoblasts into parallel networks of long, unbranched myofibers provide an in vivo-like model for examining the effects of growth factors, tension, and space flight on muscle cell growth and metabolism. To determine the feasibility of maintaining either avian or mammalian muscle organoids in a commercial perfusion bioreactor system, we measured metabolism, protein turnover. and autocrine/paracrine growth factor release rates. Medium glucose was metabolized at a constant rate in both low-serum- and serum-free media for up to 30 d. Total organoid noncollagenous protein and DNA content decreased approximately 22-28% (P < 0.05) over a 13-d period. Total protein synthesis rates could be determined accurately in the bioreactors for up to 30 h and total protein degradation rates could be measured for up to 3 wk. Special fixation and storage conditions necessary for space flight studies were validated as part of the studies. For example, the anabolic autocrine/paracrine skeletal muscle growth factors prostaglandin F2alpha (PGF2alpha) and insulin-like growth factor-1 (IGF-1) could be measured accurately in collected media fractions, even after storage at 37 degrees C for up to 10 d. In contrast, creatine kinase activity (a marker of cell damage) in collected media fractions was unreliable. These results provide initial benchmarks for long-term ex vivo studies of tissue-engineered skeletal muscle.

NASA Discipline Musculoskeletal↗

NASA NTRS1969

Plant tissue and the color infrared record

Green plant tissue should not be considered as having a uniguely high near-infrared reflectance but rather a low visual reflectance. Leaf tissue without chloroplasts appears to reflect well both visual and near infrared wavelengths. The sensitometry of color infrared film is such that a spectral imbalance strongly favoring infrared reflection is necessary to yield a red record. It is the absorption of visual light by chlorophyll that creates the imbalance that makes the typical red record for plants possible. Reflectance measurements of leaves that have been chemically blanched or which have gone into natural chloride decline strongly suggests that it is the rise in the visual reflectance that is most important in removing the imbalance and degrading the red CIR record. The role of water in leaves appears to be that of rendering epidermal membranes translucent so that the underlying chlorophyll controls the reflection rather than the leaf surface.

Pease, R. W.↗

NASA NTRS1971

Hard tissue as a composite material. I - Bounds on the elastic behavior.

Recent determination of the elastic moduli of hydroxyapatite by ultrasonic methods permits a re-examination of the Voigt or parallel model of the elastic behavior of bone, as a two phase composite material. It is shown that such a model alone cannot be used to describe the behavior of bone. Correlative data on the elastic moduli of dentin, enamel and various bone samples indicate the existence of a nonlinear dependence of elastic moduli on composition of hard tissue. Several composite models are used to calculate the bounds on the elastic behavior of these tissues. The limitations of these models are described, and experiments to obtain additional critical data are discussed.

Katz, J. L.↗

NASA NTRS1972

Cytological studies of lunar treated tissue cultures

An electron microscopic study was made of botanical materials, particularly pine tissues, treated with lunar materials collected by Apollo 12 quarantine mission. Results show unusual structural changes within several of the treated tissues. The bodies, as yet unidentified, resemble virus particles observed within infected plant cells. Although the size and shape of the structures are comparable to rod shaped virus particles such as Tobacco mosaic, the numerical distribution, affinity for stains, and intercellular location are different.

Halliwell, R. S.↗

NASA NTRS1973

Development of germ-free plants and tissue culture

The botanical program is reported for experiments performed at the Lunar Receiving Laboratory. Papers prepared during this program are listed. The studies reported include: tissues cultured on various mediums, nutritional studies, preparation of plant cultures for Apollo 15, and pine tissue cultures.

Venketeswaran, S.↗

NASA NTRS1973

Response of tobacco tissue cultures growing in contact with lunar fines.

During the quarantine periods following each Apollo mission to the moon, various biological systems were placed in the presence of lunar material to determine if pathogenic agents were present. Although no detrimental effects resulted, various responses by the several plant systems tested were noted. One such response was the increased pigmentation observed in the callus tissue cultures of tobacco. Further investigations revealed that these tissues grown in the presence of lunar material resulted in as much as a 35% increase in total pigments while differences in fatty acid and sterol concentrations were also noted when compared to the controls. It is believed that these changes brought about by the lunar material can be attributed to a change in the nutritional environment caused by its dissolution.

Weete, J. D.↗

NASA NTRS1973

The role of brown adipose tissue in temperature regulation

The thermogenetic capacities of brown adipose tissue were studied on marmots, rats and monkeys in response to cold exposure. All experiments indicated that the brown fat produced heat and slowed the cooling of tissues.

Smith, R. E.↗

NASA NTRS1974

Methodological questions of creating tissue-equivalent phantoms

On the basis of analysis and generalization of literature data, the composition of tissue equivalent plastic was justified, parameters of a standard man were determined, plaster and metal forms were created for casting dummies, and an experimental model was produced from tissue equivalent material.

Kolodkin, A. V.↗

NASA NTRS1975

Microdosimetric structure of HZE particle tracks in tissue

Heavy nuclei of the primary galactic radiation in space can have the same linear energy transfer yet greatly different lateral distribution patterns of the energy in the microstructure of tissue. Track structure thus presents itself as a new dosimetric parameter for HZE particles which is at present incompletely understood in its radiobiological significance. The theory of track structure distinguishes two regions: core and penumbra. The core is a narrow region with a radius far below 1 micron in tissue where energy deposition occurs mainly through excitations and collective oscillations of electrons. Energy density in the core accounts for slightly more than half the total LET. The penumbra surrounding the core extends laterally several to many microns depending on the energy of the primary. Energy density in the penumbra decreases steeply with the square of increasing radius. The relationships are illustrated with nuclear emulsion micrographs and plots of energy density profiles. The implications of the findings for a dosimetric system for HZE particles are discussed.

Schaefer, H. J.↗

NASA NTRS1976

Effects of water immersion to the neck on pulmonary circulation and tissue volume in man

A rapid noninvasive breathing method is used to obtain serial measurements of the pulmonary capillary blood flow, diffusing capacity per unit of alveolar volume, combined pulmonary tissue plus capillary volume, functional residual capacity, and oxygen consumption in five normal subjects undergoing 6 h of sitting, 4 h of sitting while immersed to the neck in thermoneutral water, and 4 h of lying in thermoneutral water to the neck. The rebreathing method employed a test gas mixture containing 0.5% C2H2, 0.3% C(18)O, 10% He, 21% O2, and balance N2. It is shown that immersion to the neck in the seated posture results in significant increases in sodium excretion cardiac output, and diffusing capacity per unit of alveolar volume. The pulmonary tissue plus capillary volume did not change, demonstrating that the central vascular engorgement induced by water immersion is not accompanied by significant extravasation of fluid into the pulmonary interstitial space.

Begin, R.↗

NASA NTRS1976

Method and system for in vivo measurement of bone tissue using a two level energy source

Methods and apparatus are provided for radiologically determining the bone mineral content of living human bone tissue independently of the concurrent presence of adipose and other soft tissues. A target section of the body of the subject is irradiated with a beam of penetrative radiations of preselected energy to determine the attenuation of such beam with respect to the intensity of each of two radiations of different predetermined energy levels. The resulting measurements are then employed to determine bone mineral content.

Cameron, J. R.↗