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At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Antisense oligodeoxynucleotide inhibition of a swelling-activated cation channel in osteoblast-like osteosarcoma cells

By patch-clamp analysis, we have shown that chronic, intermittent mechanical strain (CMS) increases the activity of stretch-activated cation channels of osteoblast-like UMR-106.01 cells. CMS also produces a swelling-activated whole-cell conductance (Gm) regulated by varying strain levels. We questioned whether the swelling-activated conductance was produced by stretch-activated cation channel activity. We have identified a gene involved in the increase in conductance by using antisense oligodeoxynucleotides (ODN) derived from the alpha 1-subunit genes of calcium channels found in UMR-106.01 cells (alpha1S, alpha1C, and alpha1D). We demonstrate that alpha 1C antisense ODNs abolish the increase in Gm in response to hypotonic swelling following CMS. Antisense ODNs to alpha1S and alpha1D, sense ODNs to alpha1C, and sham permeabilization had no effect on the conductance increase. In addition, during cell-attached patch-clamp studies, antisense ODNs to alpha1c completely blocked the swelling-activated and stretch-activated nonselective cation channel response to strain. Antisense ODNs to alpha1S treatment produced no effect on either swelling-activated or stretch-activated cation channel activity. There were differences in the stretch-activated and swelling-activated cation channel activity, but whether they represent different channels could not be determined from our data. Our data indicate that the alpha1C gene product is involved in the Gm and the activation of the swelling-activated cation channels induced by CMS. The possibility that swelling-activated cation channel genes are members of the calcium channel superfamily exists, but if alpha1c is not the swelling-activated cation channel itself, then its expression is required for induction of swelling-activated cation channel activity by CMS.

NASA Discipline Musculoskeletal↗
NASA NTRS1995

Cellular localization of the Ca2+ binding TCH3 protein of Arabidopsis

TCH3 is an Arabidopsis touch (TCH) gene isolated as a result of its strong and rapid upregulation in response to mechanical stimuli, such as touch and wind. TCH3 encodes an unusual calcium ion-binding protein that is closely related to calmodulin but has the potential to bind six calcium ions. Here it is shown that TCH3 shows a restricted pattern of accumulation during Arabidopsis vegetative development. These data provide insight into the endogenous signals that may regulate TCH3 expression and the sites of TCH3 action. TCH3 is abundant in the shoot apical meristem, vascular tissue, the root columella and pericycle cells that give rise to lateral roots. In addition, TCH3 accumulation in cells of developing shoots and roots closely correlates with the process of cellular expansion. Following wind stimulation, TCH3 becomes more abundant in specific regions including the branchpoints of leaf primordia and stipules, pith parenchyma, and the vascular tissue. The consequences of TCH3 upregulation by wind are therefore spatially restricted and TCH3 may function at these sites to modify cell or tissue characteristics following mechanical stimulation. Because TCH3 accumulates specifically in cells and tissues that are thought to be under the influence of auxin, auxin levels may regulate TCH3 expression during development. TCH3 is upregulated in response to low levels of exogenous indole-3-acetic acid (IAA), but not by inactive auxin-related compounds. These results suggest that TCH3 protein may play roles in mediating physiological responses to auxin and mechanical environmental stimuli.

NASA Discipline Plant Biology↗
NASA NTRS1992

Identification of a new EF-hand superfamily member from Trypanosoma brucei

We identified several open reading frames between the regions encoding calmodulin and ubiquitin-EP52/1 in the genome of Trypanosoma brucei. One of these, EFH5, encodes a protein 192 amino acids long. The EFH5 transcript is present in poly(A)+ mRNA and is present at similar levels in the mammalian bloodstream form and the insect procyclic form. EFH5 contains four EF-hand homolog domains, two of which are inferred to bind Ca2+ ions. We expressed EFH5 as a fusion protein in Escherichia coli and demonstrated calcium-binding activity of the fusion protein using the 45Ca-overlay technique. The function of EFH5 remains unknown; however, as the fourth EF-hand homolog identified in trypanosomes, it attests to the broad range of functions assumed by calcium functioning as a second messenger. EFH5, which is most closely related to LAV1-2 from Physarum, represents a distinct subfamily among the EF-hand-containing proteins.

Non-NASA Center↗
NASA NTRS1971

A lime refractory for high temperature use

Lime refractory fabrication and properties for high temperature applications, describing production of calcium oxide grain by sintering process from commercial calcium hydroxide

Benson, J. T.↗
NASA NTRS1971

The measurement of radiation exposure of astronauts by radiochemical techniques

The concentrations of 23 major, minor, and trace elements in the fecal samples from the Apollo 12 and 13 astronauts are reported. Most elemental excretion rates are comparable to rates reported for earlier missions. Exceptions are noted for calcium, iron, and tin. Body calcium and iron losses appear to be reduced during the Apollo 12 and 13 missions such that losses now seem to be insignificant. Refined measurements of tin excretion rates agree with normal dietary intakes. Earlier reported tin values are in error. A new passive dosimetry canister was designed which contains foils of tantalum, copper, titanium, iron, cobalt, aluminum, and scandium. By measuring the concentrations of the various products of nuclear reactions in these metals after space exposure, the characteristics of the incident cosmic particles can be determined.

Brodzinski, R. L.↗
NASA NTRS1972

The lunar interior

The compressional velocities are estimated for materials in the lunar interior and compared with lunar seismic results. The lower crust has velocities appropriate for basalts or anorthosites. The high velocities associated with the uppermost mantle imply high densities and a change in composition to a lighter assemblage at depths of the order of 120 km. Calcium and aluminum are probably important components of the upper mantle and are deficient in the lower mantle. Much of the moon may have accreted from material similar in composition to eucrites. The important mineral of the upper mantle is garnet; possible accessory minerals are kyanite, spinel, and rutile. If the seismic results stand up, the high velocity layer in the moon is more likely to be a high pressure form of anorthosite than eclogite, pyroxenite, or dunite. The thickness of the layer is of the order of 50 km. Cosmic abundances can be maintained if the lower mantle is ferromagnesium silicate with minimal amounts of calcium and aluminum. Achondrites such as eucrites and howardites have more of the required characteristics of the lunar interior than carbonaceous chondrites. A density inversion in the moon is a strong possibility.

Anderson, D. L.↗
NASA NTRS1972

Urinary excretion values in 2-day food-deprived, unrestrained chimpanzees.

A study was conducted to determine the baseline 24-hr urinary excretion values in the young, unrestrained chimpanzee, and also changes in urinary values, if any, induced by the two-day food deprivation stress. Urine was analyzed for volume, osmolarity, creatinine, creatine, urea nitrogen, 17-hydroxycorticosteroids (17-OHCS), 3-methoxy-4-hydroxymandelic acid (VMA), calcium, and inorganic phosphorus. Significant increases due to food deprivation stress were observed for volume, creatine, urea nitrogen, 17-OHCS, VMA, and phosphorus values, with significant decreases in osmolarity and calcium. All values approached normal levels by the second poststress day. No significant changes were observed in creatinine. A comparison is drawn between human and chimpanzee adaptation to stress.

Mcnew, J. J.↗
NASA NTRS1972

Parathyroid Hormone, Calcitonin, and Vitamin D

Analyses of secretion of parathyroid hormone during tests of stimulation and suppression of hormone-secretory activity using infusions of EDTA and calcium, respectively, have established that, in contrast to previous views, secretion of the hormone is not autonomous in many patients that have adenomatous hyperparathyroidism, but is responsive to changes in blood-calcium concentration. These findings have led to a new understanding of the pathophysiology of hormone production in hyperparathy-roidism. A related application of the diagnostic use of the radioimmunoassay is the preoperative localization of parathyroid tumors and the distinction between adenomas and chief-cell hyperplasia. Work involving catheterization and radioimmunoassay of blood samples obtained from the subclavin and innominate veins and the venae cavae, led to localization in a high percentage of patients. However, this procedure has been adopted recently to detect hormone concentration in the small veins directly draining the parathyroid glands.

Potts, J. T.↗
NASA NTRS1973

An unidentified absorption in the spectra of C-S stars

An absorption feature in the low-dispersion red spectrograms of carbon Mira variables and C-S stars shown to exhibit strikingly different behavior in these similarly appearing carbon and carbonlike stars. Evidence is presented that in the carbon Miras the feature may be due to unresolved bandheads of the (0,0) system of calcium iodide. In this group of stars the feature exhibits a temperature sensitivity similar to absorptions due to calcium chloride and to the neutral sodium doublet. No identification is suggested for the feature appearing among the C-S stars, though there is evidence against it being composed partially of a zero-volt line of neutral scandium.

Rybski, P. M.↗
NASA NTRS1974

Strongly differentiated material in high-inclination and retrograde orbits

Two definitive spectra of strongly differentiated meteors are discussed. The meteors entered the earth's atmosphere at velocities greater than 40 km/sec from high-inclination and retrograde orbits. Both were magnesium-calcium particles, and their spectra show them to be highly deficient in iron and sodium. The moon and the asteroids have been discussed as sources of such calcium-rich achondrites, but these sources give low or intermediate geocentric velocities. Long-period comets and meteoroids of probable cometary origin are the only objects now known to have orbits similar to the orbits of these two meteors.

Harvey, G. A.↗
NASA NTRS1974

Influence of bedrest and hypercapnia upon urinary mineral excretion in man

Bedrest and hypercapnia affected urinary mineral excretion. An increase in the excretion of magnesium, calcium, and inorganic phosphorus was noted during bedrest. Zinc excretion decreased during hypercapnia; however, this decrease was not significant when the experimental and preexperimental periods were compared. The combined effect of bedrest and hypercapnia was not synergistic for calcium excretion.

Giannetta, C. L.↗
NASA NTRS1976

Interstellar absorption in intercloud regions. II - Detection of the Na I lines

The weak interstellar absorption lines of Na I, Ca II, and H I formed in the intercloud medium toward seven nearly unreddened stars are analyzed. Together with the widths of the Na I and Ca II lines, the Na I/H column-density ratios determine limits on the temperature of the absorbing gas, while the Ca II/H ratios establish limits on its calcium depletion. If the electron density is about 0.02 per cu cm in the absorbing regions, two of the seven temperatures are between 3200 K and 6000 K, while three others exceed lower limits ranging from 1400 K to 6500 A. The calcium depletions generally are less severe than in a typical cloud by at least an order of magnitude.

Hobbs, L. M.↗
NASA NTRS1976

Observations of interstellar titanium toward 47 stars

Results are presented from photoelectric scans of the interstellar 3384-A line of Ti II obtained at a resolution of 3.7 km/s for 47 stars. Although the depletion of titanium from the interstellar gas is large and highly variable, its ratio to the depletion of interstellar calcium is relatively constant; titanium is less depleted than calcium by a factor of about four. A method for determining approximate electron densities from the Ca II and Ti II column densities is applied to 51 interstellar clouds.

Stokes, G. M.↗
NASA NTRS1977

Metal abundance in the Praesepe and Hyades clusters

Calcium K-line photometry is reported for 27 A-type stars in the Praesepe cluster, and the data obtained are compared with previous K-line observations of Hyades stars. It is found that calcium and other metals are generally overabundant in Praesepe relative to field stars and that there is a considerable scatter in metal-abundance indices. Comparison with the Hyades results indicates that the Praesepe stars are as metal-enriched as the Hyades stars. These results are taken as evidence favoring Eggen's (1960) proposal that the Hyades and Praesepe clusters should be regarded as a single group having, on the average, about a factor-of-two higher metal abundance than solar-neighborhood field stars as well as a high internal dispersion in metal-line strengths. The questions of where and how the Praesepe-Hyades stars acquired their high average metal abundances, K-line strengths, and associated dispersions are briefly considered.

Henry, R. C.↗
NASA NTRS1978

Strontium metabolism in the rebuilding of skeletal tissue

The relationship between calcium and strontium in bone metabolism is described. Whole body comparisons in the form of balance studies, plasma kinetics, and biochemical bone differences are briefly reviewed. The value of strontium as a qualitative calcium mimetic is established. A procedure of strontium deposition in the bones is presented as a means to study postflight bone rebuilding and to locate areas of inflight demineralization.

Source record↗
NASA NTRS1978

The center-to-limb

Center-to-limb measurements of the Ca I 6573 intercombination line and the Ca II 7324 forbidden line are compared with synthetic profiles based on a simple representation of the non-LTE Ca-Ca(+) ionization equilibrium. The effects of photoionizations from low lying excited states of neutral calcium are found to reduce the sensitivity of the 6573 center-to-limb behavior as a thermal structure diagnostic. The synthetic center-to-limb behavior is also sensitive to uncertainties in the nonthermal broadening. Nevertheless, the measured center-to-limb behavior of 6573 favors a 'cool' photospheric model over hotter models based on the Ca II K wings. The non-LTE calcium abundance obtained from the disk center equivalent widths of 6573 and 7324 using the best fit model is A(Ca) = 2.1 plus or minus 0.2 x 10 to the -6th (by number relative to hydrogen).

Source record↗
NASA NTRS1981

A 14-day ground-based hypokinesia study in nonhuman primates: A compilation of results

A 14 day ground based hypokinesia study with rhesus monkeys was conducted to determine if a spaceflight of similar duration might affect bone remodeling and calcium homeostatis. The monkeys were placed in total body casts and sacrificed either immediately upon decasting or 14 days after decasting. Changes in vertebral strength were noted and further deterioration of bone strength continued during the recovery phase. Resorption in the vertebrae increased dramatically while formation decreased. Cortical bone formation was impaired in the long bones. The immobilized animals showed a progressive decrease in total serum calcium which rebounded upon remobilization. Most mandibular parameters remained unchanged during casting except for retardation of osteon birth or maturation rate and density distribution of matrix and mineral moieties.

Kazarian, L.↗
NASA NTRS1981

Experiment K-310: The effect of spaceflight on osteogenesis and dentinogenesis in the mandibles of rats

Normal rates of dentinogenesis and osteogenesis in the body of the mandible were observed. The total calcium, inorganic phosphorus and hydroxyproline levels in the jaws and incisors of the flight rats were normal. Gravity density fractionation studies suggested, however, that spaceflight caused a delay in the normal maturation of bone mineral and matrix; normal values were reestablished by 6 days postflight. The teeth were spared. The circadian and ultradian patterns of dentin calcification were normal during spaceflight and recovery periods, but the enamel rhythms displayed a greater amplitude of sulfur concentrations and this abnormal calcium to sulfur ratios only during exposure to zero gravity. The rat mandible and teeth do not suffer the deficits of bone formation common to weight bearing parts of the skeleton during spaceflight. The only derangements detected were in the quality of the matrix and mineral moieties.

Simmons, D. J.↗