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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.

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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Reduced naphthylphthalamic acid binding in the tir3 mutant of Arabidopsis is associated with a reduction in polar auxin transport and diverse morphological defects

Polar auxin transport plays a key role in the regulation of plant growth and development. To identify genes involved in this process, we have developed a genetic procedure to screen for mutants of Arabidopsis that are altered in their response to auxin transport inhibitors. We recovered a total of 16 independent mutants that defined seven genes, called TRANSPORT INHIBITOR RESPONSE (TIR) genes. Recessive mutations in one of these genes, TIR3, result in altered responses to transport inhibitors, a reduction in polar auxin transport, and a variety of morphological defects that can be ascribed to changes in indole-3-acetic acid distribution. Most dramatically, tir3 seedlings are strongly deficient in lateral root production, a process that is known to depend on polar auxin transport from the shoot into the root. In addition, tir3 plants display a reduction in apical dominance as well as decreased elongation of siliques, pedicels, roots, and the inflorescence. Biochemical studies indicate that tir3 plants have a reduced number of N-1-naphthylphthalamic (NPA) binding sites, suggesting that the TIR3 gene is required for expression, localization, or stabilization of the NPA binding protein (NBP). Alternatively, the TIR3 gene may encode the NBP. Because the tir3 mutants have a substantial defect in NPA binding, their phenotype provides genetic evidence for a role for the NBP in plant growth and development.

Non-NASA Center↗
NASA NTRS1997

Strain activation of bovine aortic smooth muscle cell proliferation and alignment: study of strain dependency and the role of protein kinase A and C signaling pathways

Smooth muscle cell (SMC) phenotype can be altered by physical forces as demonstrated by cyclic strain-induced changes in proliferation, orientation, and secretion of macromolecules. However, the magnitude of strain required and the intracellular coupling pathways remain ill defined. To examine the strain requirements for SMC proliferation, we selectively seeded bovine aortic SMC either on the center or periphery of silastic membranes which were deformed with 150 mm Hg vacuum (0-7% center; 7-24% periphery). SMC located in either the center or peripheral regions showed enhanced proliferation compared to cells grown under the absence of cyclic strain. Moreover, SMC located in the center region demonstrated significantly (P < 0.005) greater proliferation as compared to those in the periphery. In contrast, SMC exposed to high strain (7-24%) demonstrated alignment perpendicular to the strain gradient, whereas SMC in the center (0-7%) remained aligned randomly. To determine the mechanisms of these phenomena, we examined the effect of cyclic strain on bovine aortic SMC signaling pathways. We observed strain-induced stimulation of the cyclic AMP pathway including adenylate cyclase activity and cyclic AMP accumulation. In addition, exposure of SMC to cyclic strain caused a significant increase in protein kinase C (PKC) activity and enzyme translocation from the cytosol to a particulate fraction. Further study was conducted to examine the effect of strain magnitude on signaling, particularly protein kinase A (PKA) activity as well as cAMP response element (CRE) binding protein levels. We observed significantly (P < 0.05) greater PKA activity and CRE binding protein levels in SMC located in the center as compared to the peripheral region. However, inhibition of PKA (with 10 microM Rp-cAMP) or PKC (with 5-20 ng/ml staurosporine) failed to alter either the strain-induced increase in SMC proliferation or alignment. These data characterize the strain determinants for activation of SMC proliferation and alignment. Although strain activated both the AC/cAMP/PKA and the PKC pathways in SMC, singular inhibition of PKA and PKC failed to prevent strain-induced alignment and proliferation, suggesting either their lack of involvement or the multifactorial nature of these responses.

Non-NASA Center↗
NASA NTRS1996

Neurofilament protein is differentially distributed in subpopulations of corticocortical projection neurons in the macaque monkey visual pathways

Previous studies of the primate cerebral cortex have shown that neurofilament protein is present in pyramidal neuron subpopulations displaying specific regional and laminar distribution patterns. In order to characterize further the neurochemical phenotype of the neurons furnishing feedforward and feedback pathways in the visual cortex of the macaque monkey, we performed an analysis of the distribution of neurofilament protein in corticocortical projection neurons in areas V1, V2, V3, V3A, V4, and MT. Injections of the retrogradely transported dyes Fast Blue and Diamidino Yellow were placed within areas V4 and MT, or in areas V1 and V2, in 14 adult rhesus monkeys, and the brains of these animals were processed for immunohistochemistry with an antibody to nonphosphorylated epitopes of the medium and heavy molecular weight subunits of the neurofilament protein. Overall, there was a higher proportion of neurons projecting from areas V1, V2, V3, and V3A to area MT that were neurofilament protein-immunoreactive (57-100%), than to area V4 (25-36%). In contrast, feedback projections from areas MT, V4, and V3 exhibited a more consistent proportion of neurofilament protein-containing neurons (70-80%), regardless of their target areas (V1 or V2). In addition, the vast majority of feedback neurons projecting to areas V1 and V2 were located in layers V and VI in areas V4 and MT, while they were observed in both supragranular and infragranular layers in area V3. The laminar distribution of feedforward projecting neurons was heterogeneous. In area V1, Meynert and layer IVB cells were found to project to area MT, while neurons projecting to area V4 were particularly dense in layer III within the foveal representation. In area V2, almost all neurons projecting to areas MT or V4 were located in layer III, whereas they were found in both layers II-III and V-VI in areas V3 and V3A. These results suggest that neurofilament protein identifies particular subpopulations of corticocortically projecting neurons with distinct regional and laminar distribution in the monkey visual system. It is possible that the preferential distribution of neurofilament protein within feedforward connections to area MT and all feedback projections is related to other distinctive properties of these corticocortical projection neurons.

Non-NASA Center↗
NASA NTRS1996

Neurochemical, morphologic, and laminar characterization of cortical projection neurons in the cingulate motor areas of the macaque monkey

The primate cingulate gyrus contains multiple cortical areas that can be distinguished by several neurochemical features, including the distribution of neurofilament protein-enriched pyramidal neurons. In addition, connectivity and functional properties indicate that there are multiple motor areas in the cortex lining the cingulate sulcus. These motor areas were targeted for analysis of potential interactions among regional specialization, connectivity, and cellular characteristics such as neurochemical profile and morphology. Specifically, intracortical injections of retrogradely transported dyes and intracellular injection were combined with immunocytochemistry to investigate neurons projecting from the cingulate motor areas to the putative forelimb region of the primary motor cortex, area M1. Two separate groups of neurons projecting to area M1 emanated from the cingulate sulcus, one anterior and one posterior, both of which furnished commissural and ipsilateral connections with area M1. The primary difference between the two populations was laminar origin, with the anterior projection originating largely in deep layers, and the posterior projection taking origin equally in superficial and deep layers. With regard to cellular morphology, the anterior projection exhibited more morphologic diversity than the posterior projection. Commissural projections from both anterior and posterior fields originated largely in layer VI. Neurofilament protein distribution was a reliable tool for localizing the two projections and for discriminating between them. Comparable proportions of the two sets of projection neurons contained neurofilament protein, although the density and distribution of the total population of neurofilament protein-enriched neurons was very different in the two subareas of origin. Within a projection, the participating neurons exhibited a high degree of morphologic heterogeneity, and no correlation was observed between somatodendritic morphology and neurofilament protein content. Thus, although the neurons that provide the anterior and posterior cingulate motor projections to area M1 differ morphologically and in laminar origin, their neurochemical profiles are similar with respect to neurofilament protein. This suggests that neurochemical phenotype may be a more important unifying feature for corticocortical projections than morphology.

NASA Discipline Neuroscience↗
NASA NTRS1996

Response of the neuromuscular unit to spaceflight: what has been learned from the rat model

Despite the inherent limitations placed on spaceflight investigations, much has been learned about the adaptations of the neuromuscular system to weightlessness from studies of rats flown for relatively short periods (approximately 4-22 days). Below is a summary of the major effects of spaceflight observed in muscles of rats that are not in their rapid growth stage: 1. Skeletal muscles atrophy rapidly during spaceflight; significant atrophy is observed as early as after 4 days of flight. 2. The atrophic response appears to be related to the primary function of the muscle. In the hindlimb, the relative amount of atrophy can be characterized as slow extensors > fast extensors > fast flexors. This pattern of relative atrophy does not appear to be occurring in the forelimb; however, not enough data are available to draw any definitive conclusions at this time. 3. Both slow and fast fibers atrophy during spaceflight, with the largest fibers within an individual muscle generally showing the greatest atrophic response. Interestingly, the amount of fiber atrophy appears to reach a plateau after about 14 days of flight. 4. Adaptations have been observed in the concentration and content of all muscle proteins pools, with the protein pools in slow muscles the most affected. 5. Some slow and fast fibers in predominantly slow and fast muscles show shifts in their histochemical and biochemical properties, toward those observed in a "faster" phenotype. 6. Some fibers, presumably expressing slow MHC isoforms before flight, begin to express fast MHC isoforms during flight. 7. The oxidative capacity of the muscles or fibers is relatively unaffected by spaceflight, particularly in the slow muscles. Any change in whole-body fatigability associated with spaceflight most likely reflects the loss in muscle and fiber mass. 8. The glycolytic capacity of the muscles and muscle fibers is enhanced after spaceflight. This metabolic adaptation seems to be related to the shift in the contractile proteins towards "faster" isoforms. 9. The vascularity of muscles appears to be maintained after flight, based, at least, on histological observations of capillarity. 10. The force capabilities of the muscles and fibers appear to decrease in parallel with the decreases in size, i.e., the specific tension is not significantly affected after flight. 11. Changes in the speed-related properties of the slow muscles are consistent with the adaptations in the myosin molecule, i.e., the slow muscles and some fibers in the slow muscles become "faster." 12. Some muscle fiber and neuromuscular junction damage has been observed after flight, particularly in the slow muscles. The extent of damage may be related to the amount of time that the muscles are allowed to reload before removal, i.e., in general, shorter intervals result in less fiber damage. 13. Adaptations in the motor (ventral horn) and sensory (spinal ganglia) neurons have been quite variable, but this may be related to the amount of time that the muscles are allowed to reload before removal. Morphological adaptations after relatively short periods of reloading may reflect a decrease in the activation of the neural elements during flight.

manned↗
NASA NTRS1995

Changes in diaphragm muscle collagen gene expression after acute unilateral denervation

The purpose of the present study was to examine the effects of acute (3 days) unilateral diaphragm denervation (DNV) on 1) levels of alpha 1(I) and alpha 1(III) procollagen mRNA; 2) collagen concentration [hydroxyproline (HYP)]; 3) amount of the nonreducible collagen cross-link hydroxylysylpyridinoline (HP); and 4) the passive force-length relationship of the muscle. The levels of alpha 1(I) and alpha 1(III) procollagen mRNA, HYP concentration, and amount of HP were measured in muscle segments from the midcostal region of DNV and intact (INT) hemidiaphragms of adult male Fischer 344 rats (250-300 g). The in vitro passive force-length relationship of DNV and INT hemidiaphragm was determined by lengthening and shortening the diaphragm muscle segments from 85 to 115% of optimal length at a constant velocity (0.6 optimal length/s). Three days after DNV, the level of alpha 1(I) procollagen mRNA was increased over 15-fold in the DNV hemidiaphragm compared with INT (P < 0.05), whereas the level of alpha 1(III) procollagen mRNA was increased by approximately sixfold in the DNV hemidiaphragm compared with INT (P < 0.05). Collagen (HYP) concentration did not differ between groups, averaging 8.7 and 8.9 micrograms/mg dry wt for the DNV and INT hemidiaphragms, respectively. In addition, there was no difference in the amount of the mature nonreducible collagen cross-link HP between the DNV and INT hemidiaphragms (0.66 vs. 0.76 mole HP/mole collagen, respectively). The amount of passive force developed during lengthening did not differ between DNV and INT hemidiaphragms. These data indicate that acute DNV of the hemidiaphragm is associated with an increase in the mRNA level of the two principal fibrillar collagen phenotypes in skeletal muscle. However, despite extensive muscle remodeling, the passive force-length relationship of the DNV hemidiaphragm is unaffected compared with the INT muscle.

Non-NASA Center↗
NASA NTRS1995

Lipopolysaccharide modulation of a CD14-like molecule on porcine alveolar macrophages

Cluster of differentiation antigen 14 (CD14) functions as a receptor for lipopolysaccharide (LPS) LPS-binding protein (LBP) complexes. Because LPS has varying effects on CD14 expression in vitro, we evaluated CD14 expression in response to LPS with a fully differentiated macrophage phenotype, the alveolar macrophage. By using flow microfluorometric analysis and a radioimmunoassay with an anti-human CD14 monoclonal antibody (My4) that cross-reacts with porcine CD14, we found that macrophages stimulated with LPS for 24 h exhibited a two- to fivefold increase in CD14-like antigen compared with unstimulated cells. At low concentrations of LPS, up-regulation of the CD14-like antigen was dependent on serum; at higher concentrations of LPS, serum was not required. In the absence of serum a 10-fold higher dose of LPS (10 ng/ml) was required to increase CD14-like expression. In addition, LPS-induced CD14-like up-regulation correlated with secretion of tumor necrosis factor-alpha, regardless of serum concentration. Blockade with My4 antibody significantly inhibited LPS-induced tumor necrosis factor-alpha secretion at 1 ng/ml of LPS. However, inhibition decreased as we increased the LPS concentration, suggesting the existence of CD14-independent pathways of macrophage activation in response to LPS. Alternatively, My4 may have a lower affinity for the porcine CD14 antigen than LPS, which may have only partially blocked the LPS-LBP binding site at high concentrations of LPS. Therefore, these data suggest that LPS activation of porcine alveolar macrophages for 24 h increased CD14-like receptor expression. The degree of CD14-like up-regulation was related to LPS concentration, however, activation did not require the presence of serum at high concentrations of LPS.

Non-NASA Center↗
NASA NTRS1994

Pre-metatarsal skeletal development in tissue culture at unit- and microgravity

Explant organ culture was used to demonstrate that isolated embryonic mouse pre-metatarsal mesenchyme is capable of undergoing a series of differentiative and morphogenetic developmental events. Mesenchyme differentiation into chondrocytes, and concurrent morphogenetic patterning of the cartilage tissue, and terminal chondrocyte differentiation with subsequent matrix mineralization show that cultured tissue closely parallels in vivo development. Whole mount alizarin red staining of the cultured tissue demonstrates that the extracellular matrix around the hypertrophied chondrocytes is competent to support mineralization. Intensely stained mineralized bands are similar to those formed in pre-metatarsals developing in vivo. We have adapted the culture strategy for experimentation in a reduced gravity environment on the Space Shuttle. Spaceflight culture of pre-metatarsals, which have already initiated chondrogenesis and morphogenetic patterning, results in an increase in cartilage rod size and maintenance of rod shape, compared to controls. Older pre-metatarsal tissue, already terminally differentiated to hypertrophied cartilage, maintained rod structure and cartilage phenotype during spaceflight culture.

NASA Discipline Developmental Biology↗
NASA NTRS1994

Effects of extracellular matrix proteins on macrophage differentiation, growth, and function: comparison of liquid and agar culture systems

Both spaceflight and skeletal unloading suppress the haematopoietic differentiation of macrophages (Sonnenfeld et al., Aviat. Space Environ. Med., 61:648-653, 1990; Armstrong et al., J. Appl. Physiol., 75:2734-2739, 1993). The mechanism behind this reduction in haematopoiesis has yet to be elucidated. However, changes in bone marrow extracellular matrix (ECM) may be involved. To further understand the role of ECM products in macrophage differentiation, we have performed experiments evaluating the effects of fibronectin, laminin, collagen type I, and collagen type IV on macrophage development and function. Bone marrow-derived macrophages cultured on four different ECM substrates in liquid culture medium showed less growth than those cultured on plastic. Significant morphological differences were seen on each of the substrates used. Phenotypically and functionally, as measured by class II major histocompatibility molecule (MHCII) expression, MAC-2 expression, and the secretion of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), these macrophages were similar. In contrast, bone marrow-derived macrophages cultured in suspension, using agar, showed no difference in growth when exposed to ECM proteins. However, IL-6 and TNF-alpha secretion was affected by fibronectin, laminin, collagen type I, and collagen type IV in a concentration-dependent manner. We conclude that the ECM products fibronectin, laminin, collagen type I, and collagen type IV have profound effects on macrophage development and function. Additionally, we suggest that an ECM-supplemented agar culture system provides an environment more analogous to in vivo bone marrow than does a traditional liquid culture system.

Non-NASA Center↗
NASA NTRS1994

Signal transduction pathways mediating parathyroid hormone regulation of osteoblastic gene expression

Parathyroid hormone (PTH) plays a central role in regulation of calcium metabolism. For example, excessive or inappropriate production of PTH or the related hormone, parathyroid hormone related protein (PTHrP), accounts for the majority of the causes of hypercalcemia. Both hormones act through the same receptor on the osteoblast to elicit enhanced bone resorption by the osteoclast. Thus, the osteoblast mediates the effect of PTH in the resorption process. In this process, PTH causes a change in the function and phenotype of the osteoblast from a cell involved in bone formation to one directing the process of bone resorption. In response to PTH, the osteoblast decreases collagen, alkaline phosphatase, and osteopontin expression and increases production of osteocalcin, cytokines, and neutral proteases. Many of these changes have been shown to be due to effects on mRNA abundance through either transcriptional or post-transcriptional mechanisms. However, the signal transduction pathway for the hormone to cause these changes is not completely elucidated in any case. Binding of PTH and PTHrP to their common receptor has been shown to result in activation of protein kinases A and C and increases in intracellular calcium. The latter has not been implicated in any changes in mRNA of osteoblastic genes. On the other hand activation of PKA can mimic all the effects of PTH; protein kinase C may be involved in some responses. We will discuss possible mechanisms linking PKA and PKC activation to changes in gene expression, particularly at the nuclear level.

Review↗
NASA NTRS1994

Skeletal muscle satellite cells

Evidence now suggests that satellite cells constitute a class of myogenic cells that differ distinctly from other embryonic myoblasts. Satellite cells arise from somites and first appear as a distinct myoblast type well before birth. Satellite cells from different muscles cannot be functionally distinguished from one another and are able to provide nuclei to all fibers without regard to phenotype. Thus, it is difficult to ascribe any significant function to establishing or stabilizing fiber type, even during regeneration. Within a muscle, satellite cells exhibit marked heterogeneity with respect to their proliferative behavior. The satellite cell population on a fiber can be partitioned into those that function as stem cells and those which are readily available for fusion. Recent studies have shown that the cells are not simply spindle shaped, but are very diverse in their morphology and have multiple branches emanating from the poles of the cells. This finding is consistent with other studies indicating that the cells have the capacity for extensive migration within, and perhaps between, muscles. Complexity of cell shape usually reflects increased cytoplasmic volume and organelles including a well developed Golgi, and is usually associated with growing postnatal muscle or muscles undergoing some form of induced adaptive change or repair. The appearance of activated satellite cells suggests some function of the cells in the adaptive process through elaboration and secretion of a product. Significant advances have been made in determining the potential secretion products that satellite cells make. The manner in which satellite cell proliferative and fusion behavior is controlled has also been studied. There seems to be little doubt that cellcell coupling is not how satellite cells and myofibers communicate. Rather satellite cell regulation is through a number of potential growth factors that arise from a number of sources. Critical to the understanding of this form of control is to determine which of the many growth factors that can alter satellite cell behavior in vitro are at work in vivo. Little work has been done to determine what controls are at work after a regeneration response has been initiated. It seems likely that, after injury, growth factors are liberated through proteolytic activity and initiate an activation process whereby cells enter into a proliferative phase. After myofibers are formed, it also seems likely that satellite cell behavior is regulated through diffusible factors arising from the fibers rather than continuous control by circulating factors.(ABSTRACT TRUNCATED AT 400 WORDS).

NASA Program Space Biology↗
NASA NTRS1992

Histochemical carbonic anhydrase in rat inner medullary collecting duct

Rat inner medullary collecting duct (IMCD) secretes substantial amounts of H+. However, carbonic anhydrase (CA), a concomitant of H+ secretion, has been generally reported absent in this segment. To reexamine this problem, we investigated CA and the morphological phenotypes of cells comprising the IMCD by CA histochemistry, using a modified Hansson technique with light and electron microscopy. Throughout the medulla, tubule cells exhibit histochemical CA activity. In the initial third of the inner medulla, a small proportion have features of intercalated cells and demonstrate some degree of CA activity. However, the majority population in the early portions of the IMCD appears to consist of principal cells. These also show CA staining of widely variable intensity, both among and within cells. A third cell type, previously called "IMCD cells", appears in the middle portion of the IMCD and is the only cell type present near the papilla tip. In contrast to previous reports, these "IMCD cells" have histochemical CA staining, also of highly variable intensity. These results demonstrate that stainable carbonic anhydrase to support acidification is present throughout the rat IMCD, both in intercalated cells and in some cells clearly not of this type. Therefore, the presence of CA is not specific for the intercalated cell type and suggests that other cell types may participate in acid secretion in IMCD.

NASA Discipline Musculoskeletal↗
NASA NTRS1992

Zuotin, a putative Z-DNA binding protein in Saccharomyces cerevisiae

A putative Z-DNA binding protein, named zuotin, was purified from a yeast nuclear extract by means of a Z-DNA binding assay using [32P]poly(dG-m5dC) and [32P]oligo(dG-Br5dC)22 in the presence of B-DNA competitor. Poly(dG-Br5dC) in the Z-form competed well for the binding of a zuotin containing fraction, but salmon sperm DNA, poly(dG-dC) and poly(dA-dT) were not effective. Negatively supercoiled plasmid pUC19 did not compete, whereas an otherwise identical plasmid pUC19(CG), which contained a (dG-dC)7 segment in the Z-form was an excellent competitor. A Southwestern blot using [32P]poly(dG-m5dC) as a probe in the presence of MgCl2 identified a protein having a molecular weight of 51 kDa. The 51 kDa zuotin was partially sequenced at the N-terminal and the gene, ZUO1, was cloned, sequenced and expressed in Escherichia coli; the expressed zuotin showed similar Z-DNA binding activity, but with lower affinity than zuotin that had been partially purified from yeast. Zuotin was deduced to have a number of potential phosphorylation sites including two CDC28 (homologous to the human and Schizosaccharomyces pombe cdc2) phosphorylation sites. The hexapeptide motif KYHPDK was found in zuotin as well as in several yeast proteins, DnaJ of E.coli, csp29 and csp32 proteins of Drosophila and the small t and large T antigens of the polyoma virus. A 60 amino acid segment of zuotin has similarity to several histone H1 sequences. Disruption of ZUO1 in yeast resulted in a slow growth phenotype.

NASA Discipline Exobiology↗
NASA NTRS1992

Regulation of an H-ras-related transcript by parathyroid hormone in rat osteosarcoma cells

The rat osteosarcoma cell line UMR 106-01 is a commonly used model system for the study of osteoblast function. However, it also expresses a phenotype characteristic of transformed cells. To test whether the latter could be accounted for by aberrant oncogene expression, we probed Northern blots of UMR and other osteoblastic cells with a panel of oncogene probes. These blots, when probed with a cDNA specific for v-H-ras, revealed a 7.0-kilobase (kb) H-ras-related transcript (designated HRRT) in UMR 106-01 cells that was not expressed in other osteoblastic cells. Osteoblast-enriched calvarial cells expressed the typical 1.1-kb H-ras mRNA, which was absent in UMR cells. Additionally, Western blots of lysates of UMR cells documented the presence of three proteins immunologically related to H-rasp21. To determine whether HRRT represented a recombinant retrovirus product, Northern blots were probed with a cDNA specific for the highly conserved gag-pol region of Moloney murine leukemia virus. These blots showed parallel cross-reactivity with an apparently identical transcript of 7.0 kb. The 7.0-kb transcripts detected by both v-H-ras and gag-pol probes declined to the same extent after treatment with concentrations of PTH known to inhibit proliferation of these cells. PTH regulated the abundance of HRRT in a time- and dose-dependent manner, with greatest repression of the transcript after 8 h of treatment with 10(-8) M PTH. The decrease in HRRT could not be completely accounted for by changes in transcriptional activity, as determined by nuclear run-on assays.(ABSTRACT TRUNCATED AT 250 WORDS).

Non-NASA Center↗
NASA NTRS1992

Investigation of anti-motion sickness drugs in the squirrel monkey

Early attempts to develop an animal model for anti-motion sickness drugs, using dogs and cats; were unsuccessful. Dogs did not show a beneficial effect of scopolamine (probably the best single anti-motion sickness drug for humans thus far) and the findings in cats were not definitive. The authors have developed an animal model using the squirrel monkey (Saimiri sciureus) of the Bolivian phenotype. Unrestrained monkeys in a small lucite cage were tested in an apparatus that induces motion sickness by combining vertical oscillation and horizontal rotation in a visually unrestricted laboratory environment. Signs of motion sickness were scored using a rating scale. Ten susceptible monkeys (weighing 800-1000 g) were given a total of five tests each, to establish the baseline susceptibility level. Based on the anticholinergic activity of scopolamine, the sensitivity of squirrel monkey to scopolamine was investigated, and the appropriate dose of scopolamine for this species was determined. Then various anti-motion sickness preparations were administered in subsequent tests: 100 ug scopolamine per monkey; 140 ug dexedrine; 50 ug scopolamine plus 70 ug dexedrine; 100 ug scopolamine plus 140 ug dexedrine; 3 mg promethazine; 3 mg promethazine plus 3 mg ephedrine. All these preparations were significantly effective in preventing motion sickness in the monkeys. Ephedrine, by itself, which is marginally effective in humans, was ineffective in the monkeys at the doses tried (0.3-6.0 mg). The squirrel monkey appears to be a good animal model for antimotion sickness drugs. Peripherally acting antihistamines such as astemizole and terfenadine were found to be ineffective, whereas flunarizine, and an arginine vasopressin V1 antagonist, showed significant activity in preventing motion sickness.

NASA Discipline Neuroscience↗
NASA NTRS1992

How close is close: 16S rRNA sequence identity may not be sufficient to guarantee species identity

16S rRNA (genes coding for rRNA) sequence comparisons were conducted with the following three psychrophilic strains: Bacillus globisporus W25T (T = type strain) and Bacillus psychrophilus W16AT, and W5. These strains exhibited more than 99.5% sequence identity and within experimental uncertainty could be regarded as identical. Their close taxonomic relationship was further documented by phenotypic similarities. In contrast, previously published DNA-DNA hybridization results have convincingly established that these strains do not belong to the same species if current standards are used. These results emphasize the important point that effective identity of 16S rRNA sequences is not necessarily a sufficient criterion to guarantee species identity. Thus, although 16S rRNA sequences can be used routinely to distinguish and establish relationships between genera and well-resolved species, very recently diverged species may not be recognizable.

Non-NASA Center↗
NASA NTRS1992

Studies of mineralization in tissue culture: optimal conditions for cartilage calcification

The optimal conditions for obtaining a calcified cartilage matrix approximating that which exists in situ were established in a differentiating chick limb bud mesenchymal cell culture system. Using cells from stage 21-24 embryos in a micro-mass culture, at an optimal density of 0.5 million cells/20 microliters spot, the deposition of small crystals of hydroxyapatite on a collagenous matrix and matrix vesicles was detected by day 21 using X-ray diffraction, FT-IR microscopy, and electron microscopy. Optimal media, containing 1.1 mM Ca, 4 mM P, 25 micrograms/ml vitamin C, 0.3 mg/ml glutamine, no Hepes buffer, and 10% fetal bovine serum, produced matrix resembling the calcifying cartilage matrix of fetal chick long bones. Interestingly, higher concentrations of fetal bovine serum had an inhibitory effect on calcification. The cartilage phenotype was confirmed based on the cellular expression of cartilage collagen and proteoglycan mRNAs, the presence of type II and type X collagen, and cartilage type proteoglycan at the light microscopic level, and the presence of chondrocytes and matrix vesicles at the EM level. The system is proposed as a model for evaluating the events in cell mediated cartilage calcification.

Non-NASA Center↗
NASA NTRS1990

Osteoclast cytosolic calcium, regulated by voltage-gated calcium channels and extracellular calcium, controls podosome assembly and bone resorption

The mechanisms of Ca2+ entry and their effects on cell function were investigated in cultured chicken osteoclasts and putative osteoclasts produced by fusion of mononuclear cell precursors. Voltage-gated Ca2+ channels (VGCC) were detected by the effects of membrane depolarization with K+, BAY K 8644, and dihydropyridine antagonists. K+ produced dose-dependent increases of cytosolic calcium ([Ca2+]i) in osteoclasts on glass coverslips. Half-maximal effects were achieved at 70 mM K+. The effects of K+ were completely inhibited by dihydropyridine derivative Ca2+ channel blocking agents. BAY K 8644 (5 X 10(-6) M), a VGCC agonist, stimulated Ca2+ entry which was inhibited by nicardipine. VGCCs were inactivated by the attachment of osteoclasts to bone, indicating a rapid phenotypic change in Ca2+ entry mechanisms associated with adhesion of osteoclasts to their resorption substrate. Increasing extracellular Ca2+ ([Ca2+]e) induced Ca2+ release from intracellular stores and Ca2+ influx. The Ca2+ release was blocked by dantrolene (10(-5) M), and the influx by La3+. The effects of [Ca2+]e on [Ca2+]i suggests the presence of a Ca2+ receptor on the osteoclast cell membrane that could be coupled to mechanisms regulating cell function. Expression of the [Ca2+]e effect on [Ca2+]i was similar in the presence or absence of bone matrix substrate. Each of the mechanisms producing increases in [Ca2+]i, (membrane depolarization, BAY K 8644, and [Ca2+]e) reduced expression of the osteoclast-specific adhesion structure, the podosome. The decrease in podosome expression was mirrored by a 50% decrease in bone resorptive activity. Thus, stimulated increases of osteoclast [Ca2+]i lead to cytoskeletal changes affecting cell adhesion and decreasing bone resorptive activity.

NASA Discipline Musculoskeletal↗