Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Cattle”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Quantitative molecular characterization of bovine vitreous and lens with non-invasive dynamic light scattering

The non-invasive technique of dynamic light scattering (DLS) was used to quantitatively characterize vitreous and lens structure on a molecular level by measuring the sizes of the predominant particles and mapping the three-dimensional topographic distribution of these structural macromolecules in three spatial dimensions. The results of DLS measurements in five fresh adult bovine eyes were compared to DLS measurements in model solutions of hyaluronan (HA) and collagen (Coll). In the bovine eyes DLS measurements were obtained from excised samples of gel and liquid vitreous and compared to the model solutions. Measurements in whole vitreous were obtained at multiple points posterior to the lens to generate a three-dimensional 'map' of molecular structure. The macromolecule distribution in bovine lens was similarly characterized.In each bovine vitreous (Bo Vit) specimen, DLS predominantly detected two distinct particles, which differed in diffusion properties and hence size. Comparisons with model vitreous solutions demonstrated that these most likely corresponded to the Coll and HA components of vitreous. Three-dimensional mapping of Bo Vit found heterogeneity throughout the vitreous body, with different particle size distributions for Coll and HA at different loci. In contrast, the three-dimensional distribution of lens macromolecules was more homogeneous. Thus, the non-invasive DLS technique can quantitate the average sizes of vitreous and lens macromolecules and map their three-dimensional distribution. This method to assess quantitatively the macromolecular structure of vitreous and lens should be useful for clinical as well as experimental applications in health and disease. Copyright 2001 Academic Press.

Models, Molecular↗
NASA NTRS2001

Climate-disease connections: Rift Valley Fever in Kenya

All known Rift Valley fever(RVF) outbreaks in Kenya from 1950 to 1998 followed periods of abnormally high rainfall. On an interannual scale, periods of above normal rainfall in East Africa are associated with the warm phase of the El Nino/Southern Oscillation (ENSO) phenomenon. Anomalous rainfall floods mosquito-breeding habitats called dambos, which contain transovarially infected mosquito eggs. The eggs hatch Aedes mosquitoes that transmit the RVF virus preferentially to livestock and to humans as well. Analysis of historical data on RVF outbreaks and indicators of ENSO (including Pacific and Indian Ocean sea surface temperatures and the Southern Oscillation Index) indicates that more than three quarters of the RVF outbreaks have occurred during warm ENSO event periods. Mapping of ecological conditions using satellite normalized difference vegetation index (NDVI) data show that areas where outbreaks have occurred during the satellite recording period (1981-1998) show anomalous positive departures in vegetation greenness, an indicator of above-normal precipitation. This is particularly observed in arid areas of East Africa, which are predominantly impacted by this disease. These results indicate a close association between interannual climate variability and RVF outbreaks in Kenya.

Rift Valley Fever/epidemiology/transmission↗
NASA NTRS2000

Mechanical control of cyclic AMP signalling and gene transcription through integrins

This study was carried out to discriminate between two alternative hypotheses as to how cells sense mechanical forces and transduce them into changes in gene transcription. Do cells sense mechanical signals through generalized membrane distortion or through specific transmembrane receptors, such as integrins? Here we show that mechanical stresses applied to the cell surface alter the cyclic AMP signalling cascade and downstream gene transcription by modulating local release of signals generated by activated integrin receptors in a G-protein-dependent manner, whereas distortion of integrins in the absence of receptor occupancy has no effect.

NASA Discipline Cell Biology↗
NASA NTRS2000

A pollen-specific novel calmodulin-binding protein with tetratricopeptide repeats

Calcium is essential for pollen germination and pollen tube growth. A large body of information has established a link between elevation of cytosolic Ca(2+) at the pollen tube tip and its growth. Since the action of Ca(2+) is primarily mediated by Ca(2+)-binding proteins such as calmodulin (CaM), identification of CaM-binding proteins in pollen should provide insights into the mechanisms by which Ca(2+) regulates pollen germination and tube growth. In this study, a CaM-binding protein from maize pollen (maize pollen calmodulin-binding protein, MPCBP) was isolated in a protein-protein interaction-based screening using (35)S-labeled CaM as a probe. MPCBP has a molecular mass of about 72 kDa and contains three tetratricopeptide repeats (TPR) suggesting that it is a member of the TPR family of proteins. MPCBP protein shares a high sequence identity with two hypothetical TPR-containing proteins from Arabidopsis. Using gel overlay assays and CaM-Sepharose binding, we show that the bacterially expressed MPCBP binds to bovine CaM and three CaM isoforms from Arabidopsis in a Ca(2+)-dependent manner. To map the CaM-binding domain several truncated versions of the MPCBP were expressed in bacteria and tested for their ability to bind CaM. Based on these studies, the CaM-binding domain was mapped to an 18-amino acid stretch between the first and second TPR regions. Gel and fluorescence shift assays performed with CaM and a CaM-binding synthetic peptide further confirmed MPCBP binding to CaM. Western, Northern, and reverse transcriptase-polymerase chain reaction analysis have shown that MPCBP expression is specific to pollen. MPCBP was detected in both soluble and microsomal proteins. Immunoblots showed the presence of MPCBP in mature and germinating pollen. Pollen-specific expression of MPCBP, its CaM-binding properties, and the presence of TPR motifs suggest a role for this protein in Ca(2+)-regulated events during pollen germination and growth.

NASA Discipline Plant Biology↗
NASA NTRS2000

Fibroblast growth factor-2 promotes keratan sulfate proteoglycan expression by keratocytes in vitro

Keratocytes of the corneal stroma produce a specialized extracellular matrix responsible for corneal transparency. Corneal keratan sulfate proteoglycans (KSPG) are unique products of keratocytes that are down-regulated in corneal wounds and in vitro. This study used cultures of primary bovine keratocytes to define factors affecting KSPG expression in vitro. KSPG metabolically labeled with [(35)S]sulfate decreased during the initial 2-4 days of culture in quiescent cultures with low serum concentrations (0.1%). Addition of fetal bovine serum, fibroblast growth factor-2 (FGF-2), transforming growth factor beta, or platelet derived growth factor all stimulated cell division, but only FGF-2 stimulated KSPG secretion. Combined with serum, FGF-2 also prevented serum-induced KSPG down-regulation. KSPG secretion was lost during serial subculture with or without FGF-2. Expression of KSPG core proteins (lumican, mimecan, and keratocan) was stimulated by FGF-2, and steady state mRNA pools for these proteins, particularly keratocan, were significantly increased by FGF-2 treatment. KSPG expression therefore is supported by exogenous FGF-2 and eliminated by subculture of the cells in presence of serum. FGF-2 stimulates KSPG core protein expression primarily through an increase in mRNA pools.

NASA Discipline Developmental Biology↗
NASA NTRS2000

Caveolin-1 regulates shear stress-dependent activation of extracellular signal-regulated kinase

Fluid shear stress activates a member of the mitogen-activated protein (MAP) kinase family, extracellular signal-regulated kinase (ERK), by mechanisms dependent on cholesterol in the plasma membrane in bovine aortic endothelial cells (BAEC). Caveolae are microdomains of the plasma membrane that are enriched with cholesterol, caveolin, and signaling molecules. We hypothesized that caveolin-1 regulates shear activation of ERK. Because caveolin-1 is not exposed to the outside, cells were minimally permeabilized by Triton X-100 (0.01%) to deliver a neutralizing, polyclonal caveolin-1 antibody (pCav-1) inside the cells. pCav-1 then bound to caveolin-1 and inhibited shear activation of ERK but not c-Jun NH(2)-terminal kinase. Epitope mapping studies showed that pCav-1 binds to caveolin-1 at two regions (residues 1-21 and 61-101). When the recombinant proteins containing the epitopes fused to glutathione-S-transferase (GST-Cav(1-21) or GST-Cav(61-101)) were preincubated with pCav-1, only GST-Cav(61-101) reversed the inhibitory effect of the antibody on shear activation of ERK. Other antibodies, including m2234, which binds to caveolin-1 residues 1-21, had no effect on shear activation of ERK. Caveolin-1 residues 61-101 contain the scaffolding and oligomerization domains, suggesting that binding of pCav-1 to these regions likely disrupts the clustering of caveolin-1 or its interaction with signaling molecules involved in the shear-sensitive ERK pathway. We suggest that caveolae-like domains play a critical role in the mechanosensing and/or mechanosignal transduction of the ERK pathway.

Non-NASA Center↗
NASA NTRS1999

Sensitive detection of Escherichia coli O157:H7 in food and water by immunomagnetic separation and solid-phase laser cytometry

Rapid, direct methods are needed to assess active bacterial populations in water and foods. Our objective was to determine the efficiency of bacterial detection by immunomagnetic separation (IMS) and the compatibility of IMS with cyanoditolyl tetrazolium chloride (CTC) incubation to determine respiratory activity, using the pathogen Escherichia coli O157:H7. Counterstaining with a specific fluorescein-conjugated anti-O157 antibody (FAb) following CTC incubation was used to allow confirmation and visualization of bacteria by epifluorescence microscopy. Broth-grown E. coli O157:H7 was used to inoculate fresh ground beef (<17% fat), sterile 0.1% peptone, or water. Inoculated meat was diluted and homogenized in a stomacher and then incubated with paramagnetic beads coated with anti-O157 specific antibody. After IMS, cells with magnetic beads attached were stained with CTC and then an anti-O157 antibody-fluorescein isothiocyanate conjugate and filtered for microscopic enumeration or solid-phase laser cytometry. Enumeration by laser scanning permitted detection of ca. 10 CFU/g of ground beef or <10 CFU/ml of liquid sample. With inoculated meat, the regression results for log-transformed respiring FAb-positive counts of cells recovered on beads versus sorbitol-negative plate counts in the inoculum were as follows: intercept = 1.06, slope = 0.89, and r2 = 0. 95 (n = 13). The corresponding results for inoculated peptone were as follows: intercept = 0.67, slope = 0.88, and r2 = 0.98 (n = 24). Recovery of target bacteria on beads by the IMS-CTC-FAb method, compared with recovery by sorbitol MacConkey agar plating, yielded greater numbers (beef, 6.0 times; peptone, 3.0 times; water, 2.4 times). Thus, within 5 to 7 h, the IMS-CTC-FAb method detected greater numbers of E. coli O157 cells than were detected by plating. The results show that the IMS-CTC-FAb technique with enumeration by either fluorescence microscopy or solid-phase laser scanning cytometry gave results that compared favorably with plating following IMS.

Non-NASA Center↗
NASA NTRS1999

Extracellular signal-regulated kinases 1 and 2 activation in endothelial cells exposed to cyclic strain

The aim of this study was to determine whether extracellular signal-regulated kinases 1/2 (ERK1/ERK2) are activated and might play a role in enhanced proliferation and morphological change induced by strain. Bovine aortic endothelial cells (BAEC) were subjected to an average of 6 or 10% strain at a rate of 60 cycles/min for up to 4 h. Cyclic strain caused strain- and time-dependent phosphorylation and activation of ERK1/ERK2. Peak phosphorylation and activation of ERK1/ERK2 induced by 10% strain were at 10 min. A specific ERK1/ERK2 kinase inhibitor, PD-98059, inhibited phosphorylation and activation of ERK1/ERK2 but did not inhibit the increased cell proliferation and cell alignment induced by strain. Treatment of BAEC with 2,5-di-tert-butyl-1, 4-benzohydroquinone, to deplete inositol trisphosphate-sensitive calcium storage, and gadolinium chloride, a Ca2+ channel blocker, did not inhibit the activation of ERK1/ERK2. Strain-induced ERK1/ERK2 activation was partly inhibited by the protein kinase C inhibitor calphostin C and completely inhibited by the tyrosine kinase inhibitor genistein. These data suggest that 1) ERK1/ERK2 are not critically involved in the strain-induced cell proliferation and orientation, 2) strain-dependent activation of ERK1/ERK2 is independent of intracellular and extracellular calcium mobilization, and 3) protein kinase C activation and tyrosine kinase regulate strain-induced activation of ERK1/ERK2.

NASA Discipline Cell Biology↗
NASA NTRS1998

Ceruloplasmin copper induces oxidant damage by a redox process utilizing cell-derived superoxide as reductant

Oxidative damage by transition metals bound to proteins may be an important pathogenic mechanism. Ceruloplasmin (Cp) is a Cu-containing plasma protein thought to be involved in oxidative modification of lipoproteins. We have previously shown that Cp increased cell-mediated low-density lipoprotein (LDL) oxidation by a process requiring cell-derived superoxide, but the underlying chemical mechanism(s) is (are) unknown. We now show that superoxide reduction of Cp Cu is a critical reaction in cellular LDL oxidation. By bathocuproine disulfonate (BCS) binding and by superoxide utilization, we showed that exogenous superoxide reduces a single Cp Cu atom, the same Cu required for LDL oxidation. The Cu atom remained bound to Cp during the redox cycle. Three avenues of evidence showed that vascular cells reduce Cp Cu by a superoxide-dependent process. The 2-fold higher rate of Cp Cu reduction by smooth muscle cells (SMC) compared to endothelial cells (EC) was consistent with their relative rates of superoxide release. Furthermore, Cp Cu reduction by cells was blocked by Cu,Zn superoxide dismutase (SOD1). Finally, the level of superoxide produced by EC and SMC was sufficient to cause the amount of Cu reduction observed. An important role of Cp Cu reduction in LDL oxidation was suggested by results showing that SOD1 inhibited Cp Cu reduction and LDL oxidation by SMC with equal potency, while tumor necrosis factor-alpha stimulated both processes. In summary, these results show that superoxide is a critical cellular reductant of divalent transition metals involved in oxidation, and that protein-bound Cu is a substrate for this reaction. The role of these mechanisms in oxidative processes in vivo has yet to be defined.

NASA Discipline Regulatory Physiology↗
NASA NTRS1997

Background contamination by coplanar polychlorinated biphenyls (PCBs) in trace level high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS) analytical procedures

The addition of the "dioxin-like" polychlorinated biphenyl (PCB) congeners to the assessment of risk associated with the 2,3,7,8-chlorine substituted dioxins and furans has dramatically increased the number of laboratories worldwide that are developing analytical procedures for their detection and quantitation. Most of these procedures are based on established sample preparation and analytical techniques employing high resolution gas chromatography/high resolution mass spectrometry (HRGC/HRMS), which are used for the analyses of dioxin/furans at low parts-per-trillion (ppt) levels. A significant and widespread problem that arises when using these sample preparation procedures for the analysis of coplanar PCBs is the presence of background levels of these congeners. Industrial processes, urban incineration, leaking electrical transformers, hazardous waste accidents, and improper waste disposal practices have released appreciable quantities of PCBs into the environment. This contamination has resulted in the global distribution of these compounds via the atmosphere and their ubiquitous presence in ambient air. The background presence of these compounds in method blanks must be addressed when determining the exact concentrations of these and other congeners in environmental samples. In this study reliable procedures were developed to accurately define these background levels and assess their variability over the course of the study. The background subtraction procedures developed and employed increase the probability that the values reported accurately represent the concentrations found in the samples and were not biased due to this background contamination.

Polychlorinated Biphenyls/analysis/metabolism↗
NASA NTRS1998

Localization of the ANG II type 2 receptor in the microcirculation of skeletal muscle

Only functional studies have suggested the presence of the ANG II type 2 (AT2) receptor in the microcirculation. To determine the distribution of this receptor in the rat skeletal muscle microcirculation, a polyclonal rabbit anti-rat antiserum was developed and used for immunohistochemistry and Western blot analysis. The antiserum was prepared against a highly specific and antigenic AT2-receptor synthetic peptide and was validated by competition and sensitivity assays. Western blot analysis demonstrated a prominent, single band at approximately 40 kDa in cremaster and soleus muscle. Immunohistochemical analysis revealed a wide distribution of AT2 receptors throughout the skeletal muscle microcirculation in large and small microvessels. Microanatomic studies displayed an endothelial localization of the AT2 receptor, whereas dual labeling with smooth muscle alpha-actin also showed colocalization of the AT2 receptor with vascular smooth muscle cells. Other cells associated with the microvessels also stained positive for AT2 receptors. Briefly, this study confirms previous functional data and localizes the AT2 receptor to the microcirculation. These studies demonstrate that the AT2 receptor is present on a variety of vascular cell types and that it is situated in a fashion that would allow it to directly oppose ANG II type 1 receptor actions.

NASA Discipline Cardiopulmonary↗
NASA NTRS1998

Extracellular calcium (Ca2+(o))-sensing receptor in a murine bone marrow-derived stromal cell line (ST2): potential mediator of the actions of Ca2+(o) on the function of ST2 cells

The calcium-sensing receptor (CaR) is a G protein-coupled receptor that plays key roles in extracellular calcium ion (Ca2+(o)) homeostasis by mediating the actions of Ca2+(o) on parathyroid gland and kidney. Bone marrow stromal cells support the formation of osteoclasts from their progenitors as well as the growth of hematopoietic stem cells by secreting humoral factors and through cell to cell contact. Stromal cells also have the capacity to differentiate into bone-forming osteoblasts. Bone resorption by osteoclasts probably produces substantial local increases in Ca2+(o) that could provide a signal for stromal cells in the immediate vicinity, leading us to determine whether such stromal cells express the CaR. In this study, we used the murine bone marrow-derived, stromal cell line, ST2. Both immunocytochemistry and Western blot analysis, using an antiserum specific for the CaR, detected CaR protein in ST2 cells. We also identified CaR transcripts in ST2 cells by Northern analysis using a CaR-specific probe and by RT-PCR with CaR-specific primers, followed by nucleotide sequencing of the amplified products. Exposure of ST2 cells to high Ca2+(o) (4.8 mM) or to the polycationic CaR agonists, neomycin (300 microM) or gadolinium (100 microM), stimulated both chemotaxis and DNA synthesis in ST2 cells. Therefore, taken together, our data strongly suggest that the bone marrow-derived stromal cell line, ST2, possesses both CaR protein and messenger RNA that are very similar if not identical to those in parathyroid and kidney. Furthermore, as ST2 cells have the potential to differentiate into osteoblasts, the CaR in stromal cells could participate in bone turnover by stimulating the proliferation and migration of such cells to sites of bone resorption as a result of local, osteoclast-mediated release of Ca2+(o) and, thereafter, initiating bone formation after their differentiation into osteoblasts.

NASA Discipline Musculoskeletal↗
NASA NTRS1998

Calcium-independent activation of extracellular signal-regulated kinases 1 and 2 by cyclic strain

We have previously demonstrated that cyclic strain induces extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation in endothelial cells (EC). The aim of this study was to investigate the effect of Ca2+ on the activation of ERK1/2. Bovine aortic EC were pretreated with a chelator of extracellular Ca2+, ethylaneglycol-bis(aminoethylether)-tetra-acetate (EGTA), a depleter of Ca2+ pools, 2,5-Di-(tert-butyl)-1,4-benzohydroquinone (BHQ), or a Ca2+ channel blocker, GdCl3, and subjected to an average 10 % strain at a rate of 60 cycles/min for 10 min. BHQ and GdCl3 did not inhibit the strain-induced ERK1/2 activation. Chelation of normal extracellular Ca2+ (1.8 mM) medium with EGTA (3 mM) acutely stimulated baseline phosphorylation and activation of ERK1/2, thereby obscuring any strain-induced activation of ERK1/2. However, in EC preincubated for 24 hours in Ca2+-free medium, elevated baseline phosphorylation was minimally activated by EGTA (200 microM) such that cyclic strain stimulated ERK1/2 in the presence or absence of BHQ. These results suggest a Ca2+ independence of the ERK1/2 signaling pathway by cyclic strain. Copyright 1998 Academic Press.

NASA Discipline Cell Biology↗
NASA NTRS1998

Integrin binding and mechanical tension induce movement of mRNA and ribosomes to focal adhesions

The extracellular matrix (ECM) activates signalling pathways that control cell behaviour by binding to cell-surface integrin receptors and inducing the formation of focal adhesion complexes (FACs). In addition to clustered integrins, FACs contain proteins that mechanically couple the integrins to the cytoskeleton and to immobilized signal-transducing molecules. Cell adhesion to the ECM also induces a rapid increase in the translation of preexisting messenger RNAs. Gene expression can be controlled locally by targeting mRNAs to specialized cytoskeletal domains. Here we investigate whether cell binding to the ECM promotes formation of a cytoskeletal microcompartment specialized for translational control at the site of integrin binding. High-resolution in situ hybridization revealed that mRNA and ribosomes rapidly and specifically localized to FACs that form when cells bind to ECM-coated microbeads. Relocation of these protein synthesis components to the FAC depended on the ability of integrins to mechanically couple the ECM to the contractile cytoskeleton and on associated tension-moulding of the actin lattice. Our results suggest a new type of gene regulation by integrins and by mechanical stress which may involve translation of mRNAs into proteins near the sites of signal reception.

Non-NASA Center↗
NASA NTRS1998

Origin of the catalytic activity of bovine seminal ribonuclease against double-stranded RNA

Bovine seminal ribonuclease (RNase) binds, melts, and (in the case of RNA) catalyzes the hydrolysis of double-stranded nucleic acid 30-fold better under physiological conditions than its pancreatic homologue, the well-known RNase A. Reported here are site-directed mutagenesis experiments that identify the sequence determinants of this enhanced catalytic activity. These experiments have been guided in part by experimental reconstructions of ancestral RNases from extinct organisms that were intermediates in the evolution of the RNase superfamily. It is shown that the enhanced interactions between bovine seminal RNase and double-stranded nucleic acid do not arise from the increased number of basic residues carried by the seminal enzyme. Rather, a combination of a dimeric structure and the introduction of two glycine residues at positions 38 and 111 on the periphery of the active site confers the full catalytic activity of bovine seminal RNase against duplex RNA. A structural model is presented to explain these data, the use of evolutionary reconstructions to guide protein engineering experiments is discussed, and a new variant of RNase A, A(Q28L K31C S32C D38G E111G), which contains all of the elements identified in these experiments as being important for duplex activity, is prepared. This is the most powerful catalyst within this subfamily yet observed, some 46-fold more active against duplex RNA than RNase A.

Non-NASA Center↗
NASA NTRS1997

Measurement of shear-wave velocity by ultrasound critical-angle reflectometry (UCR)

There exists a growing body of research that relates the measurement of pressure-wave velocity in bone to different physiological conditions and treatment modalities. The shear-wave velocity has been less studied, although it is necessary for a more complete understanding of the mechanical properties of bone. Ultrasound critical-angle reflectometry (UCR) is a noninvasive and nondestructive technique previously used to measure pressure-wave velocities both in vitro and in vivo. This note describes its application to the measurement of shear-wave velocity in bone, whether directly accessible or covered by soft tissue.

NASA Discipline Cardiopulmonary↗