Research Containing: stress

Mechanical unloading of bone in microgravity reduces mesenchymal and hematopoietic stem cell-mediated tissue regeneration

by cfynanon 22 August 2016in Biology & Biotechnology No comment

Mechanical loading of mammalian tissues is a potent promoter of tissue growth and regeneration, whilst unloading in microgravity can cause reduced tissue regeneration, possibly through effects on stem cell tissue progenitors. To test the specific hypothesis that mechanical unloading alters differentiation of bone marrow mesenchymal and hematopoietic stem cell lineages, we studied cellular and molecular aspects of how bone marrow in the mouse proximal femur responds to unloading in microgravity. Trabecular and cortical endosteal bone surfaces in the femoral head underwent significant bone resorption in microgravity, enlarging the marrow cavity. Cells isolated from the femoral head marrow compartment showed significant down-regulation of gene expression markers for early mesenchymal and hematopoietic differentiation, including FUT1(-6.72), CSF2(-3.30), CD90(-3.33), PTPRC(-2.79), and GDF15(-2.45), but not stem cell markers, such as SOX2. At the cellular level, in situ histological analysis revealed decreased megakaryocyte numbers whilst erythrocytes were increased 2.33 fold. Furthermore, erythrocytes displayed elevated fucosylation and clustering adjacent to sinuses forming the marrow-blood barrier, possibly providing a mechanistic basis for explaining spaceflight anemia. Culture of isolated bone marrow cells immediately after microgravity exposure increased the marrow progenitor’s potential for mesenchymal differentiation into in-vitro mineralized bone nodules, and hematopoietic differentiation into osteoclasts, suggesting an accumulation of undifferentiated progenitors during exposure to microgravity. These results support the idea that mechanical unloading of mammalian tissues in microgravity is a strong inhibitor of tissue growth and regeneration mechanisms, acting at the level of early mesenchymal and hematopoietic stem cell differentiation.

Shear stress induces preimplantation embryo death that is delayed by the zona pellucida and associated with stress-activated protein kinase-mediated apoptosis

by cfynanon 9 June 2015in Biology & Biotechnology No comment

In this study, we discovered that embryos sense shear stress and sought to characterize the kinetics and the enzymatic mechanisms underlying induction of embryonic lethality by shear stress. Using a rotating wall vessel programmed to produce 1.2 dynes/cm2 shear stress, it was found that shear stress caused lethality within 12 h for E3.5 blastocysts. Embryos developed an approximate 100% increase in mitogen-activated protein kinase 8/9 (formerly known as stress-activated protein kinase/junC kinase 1/2) phosphorylation by 6 h of shear stress that further increased to approximately 350% by 12 h. Terminal deoxynucleotidyltransferase dUTP nick end labeling/apoptosis was at baseline levels at 6 h and increased to approximately 500% of baseline at 12 h, when irreversible commitment to death occurred. A mitogen-activated protein kinase 8/9 phosphorylation inhibitor, D-JNKI1, was able to inhibit over 50% of the apoptosis, suggesting a causal role for mitogen-activated protein kinase 8/9 phosphorylation in the shear stress-induced lethality. The E2.5 (compacted eight-cell/early morula stage) embryo was more sensitive to shear stress than the E3.5 (early blastocyst stage) embryo. Additionally, zona pellucida removal significantly accelerated shear stress-induced lethality while having no lethal effect on embryos in the static control. In conclusion, preimplantation embryos sense shear stress, chronic shear stress is lethal, and the zona pellucida lessens the lethal and sublethal effects of shear stress. Embryos in vivo would not experience as high a sustained velocity or shear stress as induced experimentally here. Lower shear stresses might induce sufficient mitogen-activated protein kinase 8/9 phosphorylation that would slow growth or cause premature differentiation if the zona pellucida were not intact.

Effects of parabolic flight and spaceflight on the endocannabinoid system in humans

by cfynanon 9 June 2015in Biology & Biotechnology No comment

The endocannabinoid system (ECS) plays an important role in the regulation of physiological functions, from stress and memory regulation to vegetative control and immunity. The ECS is considered a central and peripheral stress response system to emotional or physical challenges and acts through endocannabinoids (ECs), which bind to their receptors inducing subsequent effecting mechanisms. In our studies, the ECS responses have been assessed through blood concentrations of the ECs anandamide and 2-arachidonoylglycerol. In parallel, saliva cortisol was determined and the degree of perceived stress was quantified by questionnaires. This report summarizes the reactivity of the ECS in humans subjected to brief periods of kinetic stress and weightlessness during parabolic flights and to prolonged stress exposure during life onboard the International Space Station (ISS). Both conditions resulted in a significant increase in circulating ECs. Under the acute stress during parabolic flights, individuals who showed no evidence of motion sickness were in low-stress conditions and had a significant increase of plasma ECs. In contrast, highly stressed individuals with severe motion sickness had an absent EC response and a massive increase in hypothalamic-pituitary-adrenal axis activity. Likewise, chronic but well-tolerated exposure to weightlessness and emotional and environmental stressors on the ISS for 6 months resulted in a sustained increase in EC blood concentrations, which returned to baseline values after the cosmonauts’ return. These preliminary results suggest that complex environmental stressors result in an increase of circulating ECs and that enhanced EC signaling is probably required for adaptation and tolerance under stressful conditions.

[Hemopoietic status of rats exposed to weightlessness]

by cfynanon 9 June 2015in Biology & Biotechnology No comment

This paper summarizes experimental data on the erythropoiesis of rats flown on Cosmos biosatellites for 18-22 days. The histogenesis of the hemopoietic tissue is investigated at the level of stem cells, dividing-maturing pool and mature blood cells (erythrocytes). In weightlessness inhibition of the erythropoiesis in various skeletal sites occurs. Flight data are compared with hemopoietic findings in hypokinetic rats. Possible mechanisms underlying red blood disorders in humans during space flight are discussed. [References: 17]

Expansion of mammalian neural stem cells in bioreactors: effect of power input and medium viscosity

by cfynanon 9 June 2015in Biology & Biotechnology No comment

Multipotent neural precursors can be cultured in suspension bioreactors as aggregates of stem cells and progenitor cells. However, it is important to limit the size of the aggregates, as necrotic centers may develop at very large diameters. Previously, we have shown that the hydrodynamics within a suspension bioreactor can be used to control the diameter of NSC aggregates (D-MAVO < 150 μm) below sizes where necrosis would be expected to occur. In the present study, power law correlations were developed for our bioreactors showing the dependence of the maximum mean aggregate diameter on both the kinematic viscosity of the medium and the power input per unit mass of medium, The power input was manipulated by changing the agitation rate (60-100 rpm), and the viscosity was manipulated through the addition of non-toxic levels of carboxymethylcellulose. The study also confirmed that the maximum liquid shear generated at the surface of the aggregates was sufficient to dislodge single cells, thus limiting the maximum diameter of the aggregates, without causing cell damage (τ(max) = 9.76 dyn/cm(2)). This is a first step in the development of a reproducible, scaled-up process for the production of neural stem cells for therapeutic applications including the treatment of neurodegenerative disorders and acute central nervous system injuries. (C) 2002 Elsevier Science B.V. All rights reserved.

Related URLs:
<Go to ISI>://WOS:000175354200011

Simulation models of weightlessness in mammalian's developmental program

by cfynanon 9 June 2015in Biology & Biotechnology No comment

[Reproductive function of the male rat after a flight on the Kosmos-1129 biosatellite]

by cfynanon 9 June 2015in Biology & Biotechnology No comment

Male rats that were flown for 18.5 days on Cosmos-1129 were mated postflight with intact females. The mating 5 days postflight when the ejaculate consisted of spermatozoids that were exposed to zero-g effects in the mature stage yielded the litter which lagged behind the controls with respect to the growth and development during the first postnatal month. The mating 2.5-3 months postflight when the ejaculate consisted of spermatozoids that were exposed to zero-g effects at the stem cell stage yielded the litter which did not differ from the control.

Hydrodynamic Modulation of Embryonic Stem Cell Differentiation by Rotary Orbital Suspension Culture

by cfynanon 9 June 2015in Biology & Biotechnology No comment

Embryonic stern cells (ESCs) can differentiate into all somatic cell types, but the development of effective strategies to direct ESC fate is dependent upon defining environmental parameters capable of influencing cell phenotype. ESCs are commonly differentiated via cell aggregates referred to as embryoid bodies (EBs), but Current culture methods, Such as hinging drop and static Suspension, yield relatively few or heterogeneous populations of EBs. Alternatively, rotary orbital suspension culture enhances EB formation efficiency, cell yield, and homogeneity without adversely affecting differentiation. Thus, the objective of this study was to systematically examine the effects of hydrodynamic conditions created by rotary orbital shaking on EB firmation, structure, and differentiation. Mouse ESCs introduced to suspension culture at a range of rotary orbital speeds (20-60 rpm) exhibited variable EB formation sizes and yields due to differences in the kinetics of cell aggregation. Computational fluid dynamic analyses indicated that rotary orbital shaking generated relatively uniform and mild shear stresses (<= 2.5 dyn/cm(2)) within the regions EBs occupied in culture dishes, at each of the orbital speeds examined. The hydrodynamic conditions modulated EB Structure, indicated by differences in the cellular organization and morphology of the spheroids. Compared to static Culture, exposure to hydrodynamic conditions significantly altered the gene expression profile of EBs. Moreover, varying rotary orbital speeds differentially modulated the kinetic profile of gene expression and relative percentages of differentiated cell types. Over-all, this Study demonstrates that manipulation of hydrodynamic environments modulates ESC differentiation, thus providing a novel, scalable approach to integrate into the development of directed stem cell differentiation strategies. Biotechnol. Bioeng. 2010;105: 611-626. (C) 2009 Wiley Periodicals

Related URLs:
<Go to ISI>://WOS:000273799100017

Formation and differentiation of three-dimensional rat marrow stromal cell culture on microcarriers in a rotating-wall vessel

by cfynanon 9 June 2015in Biology & Biotechnology No comment

Using a high aspect ratio vessel (HARV), this study investigated the formation of 3-D rat marrow stromal cell culture on microcarriers and the expression of bone-related biochemical markers under conditions of simulated microgravity. In addition, it calculated the shear stresses imparted on the surface of microcarriers of different densities by the medium fluid in an HARV. Secondary rat marrow stromal cells were cultured on two types of microcarriers, Cytodex-3 beads and modified bioactive glass particles. Examination of cellular morphology by scanning electron microscopy revealed the presence of three-dimensional multicellular aggregates consisting of multiple cell-covered Cytodex-3 microcarriers bridged together. Mineralization was observed in the aggregates. Spherical cell-bead aggregates were observed in an HARV, while cell-bead assemblies were mostly loosely packed in a chainlike or branched structure in a cell bag. The expressions of alkaline phosphatase activity, collagen type I, and osteopontin were shown via the use of histochemical staining, immunolabeling, and confocal scanning electron microscopy. Using a numerical approach, it was found that at a given rotational speed and for a given culture medium, a larger density difference between the microcarrier and the culture medium (e.g., a modified bioactive glass particle) imparted a higher maximum shear stress on the microcarrier.

Related URLs:
<Go to ISI>://WOS:000072925300005

Epstein-Barr virus shedding by astronauts during space flight

by cfynanon 9 June 2015in Biology & Biotechnology No comment

Patterns of Epstein-Barr virus (EBV) reactivation in 32 astronauts and 18 healthy age-matched control subjects were characterized by quantifying EBV shedding. Saliva samples were collected from astronauts before, during, and after 10 space shuttle missions of 5-14 days duration. At one time point or another, EBV was detected in saliva from each of the astronauts. Of 1398 saliva specimens from 32 astronauts, polymerase chain reaction analysis showed that 314 (23%) were positive for EBV DNA. Examination by flight phase showed that 29% of the saliva specimens collected from 28 astronauts before flight were positive for EBV DNA, as were 16% of those collected from 25 astronauts during flight and 16% of those collected after flight from 23 astronauts. The mean number of EBV copies from samples taken during the flights was 417 per mL, significantly greater (p<.05) than the number of viral copies from the preflight (40) and postflight (44) phases. In contrast, the control subjects shed EBV DNA with a frequency of 3.7% and mean number of EBV copies of 40 per mL of saliva. Ten days before flight and on landing day, titers of antibody to EBV viral capsid antigen were significantly (p<.05) greater than baseline levels. On landing day, urinary levels of cortisol and catecholamines were greater than their preflight values. In a limited study (n=5), plasma levels of substance P and other neuropeptides were also greater on landing day. Increases in the number of viral copies and in the amount of EBV-specific antibody were consistent with EBV reactivation before, during, and after space flight.

Current RFI

Researcher Interviews

Recent Posts

Projects in Flight

Recently Added Research

Popular Tags

Research Containing: stress

Mechanical unloading of bone in microgravity reduces mesenchymal and hematopoietic stem cell-mediated tissue regeneration

Shear stress induces preimplantation embryo death that is delayed by the zona pellucida and associated with stress-activated protein kinase-mediated apoptosis

Effects of parabolic flight and spaceflight on the endocannabinoid system in humans

[Hemopoietic status of rats exposed to weightlessness]

Expansion of mammalian neural stem cells in bioreactors: effect of power input and medium viscosity

Simulation models of weightlessness in mammalian's developmental program

[Reproductive function of the male rat after a flight on the Kosmos-1129 biosatellite]

Hydrodynamic Modulation of Embryonic Stem Cell Differentiation by Rotary Orbital Suspension Culture

Formation and differentiation of three-dimensional rat marrow stromal cell culture on microcarriers in a rotating-wall vessel

Epstein-Barr virus shedding by astronauts during space flight