SEARCH · PubMed Health

Results for “Gravity, Altered”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 631 records · Page 35Linked to original sources

PubMedDate not supplied

Effect of unilateral common carotid artery occlusion on levels of prostaglandins D2, F2 alpha and 6-keto-prostaglandin F1 alpha in gerbil brain.

The concentrations of the arachidonic acid metabolites, PGD2, PGF2 alpha and 6-keto-PGF1 alpha, were measured in the cerebral hemispheres of gerbils subjected to unilateral carotid occlusion. Approximately 37 percent of the animals with occlusion had symptoms of cerebral ischemia. In those animals PGD2 and PGF2 alpha levels were elevated in both hemispheres. The levels of 6-keto-PGF1 alpha increased only slightly. There was no change of prostaglandin levels in asymptomatic animals. Indomethacin inhibited the increase in the levels of these arachidonic acid metabolites but did not alter brain swelling as judged by a decrease in specific gravity after 6 hours occlusion.

Animals↗

PubMed2000

The origin of contraversive pushing: evidence for a second graviceptive system in humans.

BACKGROUND: Stroke patients may exhibit the peculiar behavior of actively pushing away from the nonhemiparetic side, leading to lateral postural imbalance and a tendency to fall toward the paralyzed side. This phenomenon has been called the "pusher syndrome." OBJECTIVE: The current study analyzes the mechanism leading to contraversive pushing. METHODS: The subjective postural vertical (SPV) and subjective visual vertical (SVV) were determined in five consecutively admitted patients with severe contraversive pushing and in controls. Whereas adjustment of the SPV reflects the perceived upright orientation of the body, the SVV provides a sensitive and direction-specific measurement of peripheral and central vestibular dysfunction. RESULTS: The deficit leading to contraversive pushing is an altered perception of the body's orientation in relation to gravity. Pusher patients experience their body as oriented "upright" when it is tilted 18 degrees to the nonhemiparetic, ipsilesional side. In contrast, perception of the SVV was undisturbed. CONCLUSIONS: A separate pathway seems to be present in humans for sensing the orientation of gravity apart from the one for orientation perception of the visual world. This second graviceptive system decisively contributes to humans' control of upright body posture. Contraversive pushing occurring after stroke lesions may represent the behavioral correlate of a disturbed neural representation of this system.

Adult↗

PubMed2004

[Criteria of severity of intractable focal epilepsy in adults].

The most important criteria of severity of intractable focal epilepsies are the high frequency of seizure and the type of seizure, in particular seizures with fall. However, the presence of a brain lesion and its localization, handicap, number of antiepileptic drugs, poor social integration, history of status epilepticus, mortality, traumas, cognitive impairments, depressive symptoms and alteration of quality-of-life are also criteria of gravity. In this article, we propose a review of these various elements limiting our discussion to adults.

Accidental Falls↗

PubMed1993

[Combined viral-mycoplasma placentitis].

265 placentas were studied by means of light and fluorescent microscopy. 82 placentas showed combined infections induced by 2-5 agents (various viruses and mycoplasmas). Bacterial and fungal placentitis were excluded Manifestations depended on the infectious agents, their number and variants of their combination. Enhancement of vascular damage was observed in placentitis with participation of myxoviruses and herpes simplex virus. Enhancement of lymphoplasmacytic infiltration and sclerosis was typical for combined placentitis as well as alteration of antibody formation and interferon production. This reflects the gravity of the infection and its spread to the extra-placental membranes.

Antibody Formation↗

PubMed1994

[Benign paroxysmal positional vertigo. Differential diagnosis of posterior, horizontal and anterior canalolithiasis].

Evidence is presented that all typical features of benign paroxysmal positioning vertigo can be explained by canalolithiasis rather than by cupulolithiasis. A free floating clot of "heavy" inorganic particles gravitates to the most dependent part of the canal as soon as the patient's head is moved in a way that alters the angle between the canal's plane and the gravity vector. Based on the canalolithiasis mechanism we describe how characteristics of the thus elicited nystagmus differ if the posterior, the horizontal or the anterior semicircular canal is causative.

Calculi↗

PubMed1993

Current view of the mechanism of benign paroxysmal positioning vertigo: cupulolithiasis or canalolithiasis?

Theoretical evidence is presented that all the typical features of BPPV (benign paroxysmal positioning vertigo) cannot be explained by cupulolithiasis in that otoconial debris become settled on the cupula of the posterior semicircular canal. A free floating clot of inorganic particles (heavier than endolymph) in the ampullofugal branch of the posterior semicircular canal is more likely to cause the syndrome. The clot always gravitates to the most dependent part of the canal as soon as the patient's head is moved in a way that alters the angle between the canal's plane and the gravity vector. As compared to a plunger (depending on the direction it moves) the clot produces push or pull forces on the cupula, thereby eliciting the BPPV attack. This clot-induced endolymph flow mechanism is compatible with all features of BPPV such as latency, limited duration, fatigability, change in direction of the induced nystagmus, and the efficacy of physical therapy in both posterior and horizontal semicircular canal BPPV. The floating clot is only activated by changes in position of the head relative to the gravitational vector (positioning vertigo) but not by prolonged static positions of the head (positional vertigo), which fits clinical experience. Therefore, canalolithiasis rather than cupulolithiasis provides a better definition of the underlying mechanism in BPPV.

Endolymph↗

PubMed2006

Isolation and characterization of brewer's yeast variants with improved fermentation performance under high-gravity conditions.

To save energy, space, and time, today's breweries make use of high-gravity brewing in which concentrated medium (wort) is fermented, resulting in a product with higher ethanol content. After fermentation, the product is diluted to obtain beer with the desired alcohol content. While economically desirable, the use of wort with an even higher sugar concentration is limited by the inability of brewer's yeast (Saccharomyces pastorianus) to efficiently ferment such concentrated medium. Here, we describe a successful strategy to obtain yeast variants with significantly improved fermentation capacity under high-gravity conditions. We isolated better-performing variants of the industrial lager strain CMBS33 by subjecting a pool of UV-induced variants to consecutive rounds of fermentation in very-high-gravity wort (>22 degrees Plato). Two variants (GT336 and GT344) showing faster fermentation rates and/or more-complete attenuation as well as improved viability under high ethanol conditions were identified. The variants displayed the same advantages in a pilot-scale stirred fermenter under high-gravity conditions at 11 degrees C. Microarray analysis identified several genes whose altered expression may be responsible for the superior performance of the variants. The role of some of these candidate genes was confirmed by genetic transformation. Our study shows that proper selection conditions allow the isolation of variants of commercial brewer's yeast with superior fermentation characteristics. Moreover, it is the first study to identify genes that affect fermentation performance under high-gravity conditions. The results are of interest to the beer and bioethanol industries, where the use of more-concentrated medium is economically advantageous.

Beer↗

PubMed2004

The promotion of gravitropism in Arabidopsis roots upon actin disruption is coupled with the extended alkalinization of the columella cytoplasm and a persistent lateral auxin gradient.

The actin cytoskeleton has been implicated in regulating plant gravitropism. However, its precise role in this process remains uncertain. We have shown previously that disruption of the actin cytoskeleton with Latrunculin B (Lat B) strongly promoted gravitropism in maize roots. These effects were most evident on a clinostat as curvature that would exceed 90 degrees despite short periods of horizontal stimulation. To probe further the cellular mechanisms underlying these enhanced gravity responses, we extended our studies to roots of Arabidopsis. Similar to our observations in other plant species, Lat B enhanced the response of Arabidopsis roots to gravity. Lat B (100 nm) and a stimulation time of 5-10 min were sufficient to induce enhanced bending responses during clinorotation. Lat B (100 nm) disrupted the fine actin filament network in different regions of the root and altered the dynamics of amyloplasts in the columella but did not inhibit the gravity-induced alkalinization of the columella cytoplasm. However, the duration of the alkalinization response during continuous gravistimulation was extended in Lat B-treated roots. Indirect visualization of auxin redistribution using the DR5:beta-glucuronidase (DR5:GUS) auxin-responsive reporter showed that the enhanced curvature of Lat B-treated roots during clinorotation was accompanied by a persistent lateral auxin gradient. Blocking the gravity-induced alkalinization of the columella cytoplasm with caged protons reduced Lat B-induced curvature and the development of the lateral auxin gradient. Our data indicate that the actin cytoskeleton is unnecessary for the initial perception of gravity but likely acts to downregulate gravitropism by continuously resetting the gravitropic-signaling system.

Actins↗

PubMed1997

[New approaches to diagnosis of hysteria].

Postural stability or fluctuation of general centre of gravity (GCG) was investigated in 14 patients with hysteric motor disorders(alterations of statics and walking, pseudopareses) by means of stabilograph. Comparative groups included 7 patients with hemipareses of vascular origin, 7 patients with multiple sclerosis with spastico and atactic disturbances and 7 healthy individuals. The amplitudes of GCG fluctuations in both sagittal and frontal planes as well as their correlations were analysed. It was shown that amplitude of GCG vibration was maximal in hysteriac patients. However patterns of regulation of postural control in hysteriac patients (correlation of amplitudes of vibrations in sagittal and frontal planes) were similar to those of healthy individuals and differed significantly from organic models.

Adult↗

PubMed1975

[Clinico-statistical data on the sexualtiy of the male diabetic].

In 60 male diabetics aged between 16 and 60 followed up for 5 years, libido was found to be reduced in 58% and potency in 63%. The alteration in sex function would not appear to be related to the duration or gravity of the diseases, nor with the existence of vasculopathy; it was, however, related to age (a prevalence in elderly subjects) and to the existence of neuropathy. In one third of subjects, impotence preceded or was contemporaneous with clinical diagnosis of diabetes. Spermiogenesis alterations, present in more than half the cases, were closely related to gonadotropinuria LH; this finding, added to personal results and those obtained previously by other researchers, suggests a two-fold hypophyseal and Leydigian pathogenesis of impotence in the diabetic.

Adolescent↗

PubMed2003

The ARG1-LIKE2 gene of Arabidopsis functions in a gravity signal transduction pathway that is genetically distinct from the PGM pathway.

The arl2 mutants of Arabidopsis display altered root and hypocotyl gravitropism, whereas their inflorescence stems are fully gravitropic. Interestingly, mutant roots respond like the wild type to phytohormones and an inhibitor of polar auxin transport. Also, their cap columella cells accumulate starch similarly to wild-type cells, and mutant hypocotyls display strong phototropic responses to lateral light stimulation. The ARL2 gene encodes a DnaJ-like protein similar to ARG1, another protein previously implicated in gravity signal transduction in Arabidopsis seedlings. ARL2 is expressed at low levels in all organs of seedlings and plants. arl2-1 arg1-2 double mutant roots display kinetics of gravitropism similar to those of single mutants. However, double mutants carrying both arl2-1 and pgm-1 (a mutation in the starch-biosynthetic gene PHOSPHOGLUCOMUTASE) at the homozygous state display a more pronounced root gravitropic defect than the single mutants. On the other hand, seedlings with a null mutation in ARL1, a paralog of ARG1 and ARL2, behave similarly to the wild type in gravitropism and other related assays. Taken together, the results suggest that ARG1 and ARL2 function in the same gravity signal transduction pathway in the hypocotyl and root of Arabidopsis seedlings, distinct from the pathway involving PGM.

Amino Acid Sequence↗

PubMed1999

Ultrastructural observation of altered chloroplast morphology in space-grown Brassica rapa cotyledons.

Photosynthesis will be indispensable in a bioregenerative life-support systems for long space missions. It is critical understand the effects of space on this complex process, especially the loss of gravity. Past has noted changes in plant growth and development; differences about cell size, shape, division, and differentiation; and plastid distribution and structure alterations. The amyloplast-containing columelar cells in root tips were carefully examined since they are likely gravity-sensing sites. Changes on photosynthetic physiology and chloroplast structure have been reported. Both increases and decreases of chlorophyll and carotenoid contents were reported. Structural changes of thylakoid membranes in chloroplasts were observed in pea and Arabidopsis grown in space or clinorotation. Recently, a decrease of CO2 assimilation rate and of electron transport rate of both PSI and PSII on thylakoid membranes were reported in space-grown wheat. These imply an overall decrease of photosynthetic activities, and implicate thylakoid-old structural changes. For example, PSI activity, and its reaction center subunits (PsaA, PsaB, and PsaC) and the LHCIs, were decreased under microgravity. Here, we further examined cellular morphology and ultrastructural features of the chloroplast and its thylakoid membranes by electron microscopy and in situ immunolocalization.

Brassica↗

PubMed1999

Toxicity of a particulate formulation for the intraperitoneal application of mitoxantrone.

Mitoxantrone (MXN) has demonstrated therapeutic efficacy in the intraperitoneal treatment of malignancies. However, severe local toxicity is dose limiting. Therefore, a particulate formulation of MXN, the drug incorporated in albumin microspheres, was evaluated concerning tolerability. Survival rates as well as alterations in body weight, food intake, water intake, urine volume, urine specific gravity, urine protein content, and complete blood count were observed following single or multiple intraperitoneal injections of MXN solution, dispersions containing MXN-loaded microspheres or unloaded microspheres, and the injection vehicle to female and male Sprague-Dawley rats. Applied MXN dosage was equivalent to 30 mg/m2 body surface area. Unloaded microspheres were well tolerated without signs of toxicity. Application of MXN solution or MXN-loaded microspheres resulted in similar survival rates (56% 9 weeks after single injection) and in a comparable bone marrow toxicity (mainly leucopenia). Body weight, food and water intake as well as urine volume were decreased following application of MXN solution, whereas a progressive gain in weight and no remarkable alterations in nutrition and urine excretion were noted after administration of MXN-loaded and unloaded microspheres, or of the injection vehicle. In conclusion, intraperitoneal injection of MXN incorporated in albumin microspheres exhibits in part less toxicity than conventional treatment.

Animals↗

PubMed1988

Further studies of effects of sodium aluminosilicate on egg shell quality.

Five experiments were conducted using 36 dietary treatments to compare chloride salts and HCl as chemical sources of Cl for the adjustment of dietary Cl when using sodium aluminosilicate (SAS), to compare SAS to natural zeolites (clinoptilolite and mordenite), and to determine the appropriate level of dietary SAS for optimum egg specific gravity. The methods of Na and Cl correction used in the various treatments included altering the levels of NaCl, calcium chloride (CaCl2), potassium chloride (KCl), magnesium chloride (MgCl2), iron chloride (FeCl3), or hydrochloric acid (HCl). Experimental diets were fed for 6 to 8 wk. Results of all experiments (except Experiment 2) indicated that the addition of SAS to layer diets improved egg specific gravity and that correction for Na by removal of NaCl and the addition of HCl was not necessary for SAS to be effective. No beneficial effects of dietary SAS on egg specific gravity were observed when Na and Cl corrections were made using CaCl2, KCl, MgCl2, or FeCl3. The feeding of SAS has no influence on egg production in Experiments 1 and 3 but significantly improved egg production in Experiment 4, when it was added to diets containing 2.75% Ca. An adverse effect on production of feeding SAS was observed, especially at the higher levels of SAS in Experiments 2 and 5. In general, SAS tended to reduce feed consumption, with no effect on egg weight. It was concluded that .75% SAS will improve egg specific gravity approximately 1 to 3 units and that correction for Na was not necessary for SAS to be effective.

Aluminum Silicates↗

PubMed2004

The effect of radial head excision and arthroplasty on elbow kinematics and stability.

BACKGROUND: Radial head fractures are common injuries. Comminuted radial head fractures often are treated with radial head excision with or without radial head arthroplasty. The purpose of the present study was to determine the effect of radial head excision and arthroplasty on the kinematics and stability of elbows with intact and disrupted ligaments. We hypothesized that elbow kinematics and stability would be (1) altered after radial head excision in elbows with intact and disrupted ligaments, (2) restored after radial head arthroplasty in elbows with intact ligaments, and (3) partially restored after radial head arthroplasty in elbows with disrupted ligaments. METHODS: Eight cadaveric upper extremities were studied in an in vitro elbow simulator that employed computer-controlled actuators to govern tendon-loading. Testing was performed in stable, medial collateral ligament-deficient, and lateral collateral ligament-deficient elbows with the radial head intact, with the radial head excised, and after radial head arthroplasty. Valgus angulation and rotational kinematics were determined during passive and simulated active motion with the arm dependent. Maximum varus-valgus laxity was measured with the arm in a gravity-loaded position. RESULTS: In specimens with intact ligaments, elbow kinematics were altered and varus-valgus laxity was increased after radial head excision and both were corrected after radial head arthroplasty. In specimens with disrupted ligaments, elbow kinematics were altered after radial head excision and were similar to those observed in specimens with a native radial head after radial head arthroplasty. Varus-valgus laxity was increased after ligament disruption and was further increased after radial head excision. Varus-valgus laxity was corrected after radial head arthroplasty and ligament repair; however, it was not corrected after radial head arthroplasty without ligament repair. CONCLUSIONS: Radial head excision causes altered elbow kinematics and increased laxity. The kinematics and laxity of stable elbows after radial head arthroplasty are similar to those of elbows with a native radial head. However, radial head arthroplasty alone may be insufficient for the treatment of complex fractures that are associated with damage to the collateral ligaments as arthroplasty alone does not restore stability to elbows with ligament injuries.

Aged↗

PubMed2002

Reduced gravitropism in inflorescence stems and hypocotyls, but not roots, of Arabidopsis mutants with large plastids.

The sites of gravity perception are columella cells in roots and endodermal cells in hypocotyls and inflorescence stems. Since plastids are likely to play a role in graviperception, we investigated gravitropism in plastid mutants of Arabidopsis. Previous studies have shown that the arc6 and arc12 (accumulation and replication of chloroplasts) mutants have an average of two large plastids per leaf mesophyll cell. In this study, we found that these arc mutants have altered plastid morphology throughout the entire plant body, including the cells involved in gravity perception. There were no major differences in total starch content per cell in endodermal and columella cells of the wild-type (WT) compared to arc6 and arc12 as assayed by iodine staining. Thus, the total mass of plastids per cell in arc6 and arc12 is similar to their respective WT strains. Results from time course of curvature studies demonstrated that the plastid mutation affected gravitropism only of inflorescence stems and hypocotyls, but not roots. Thus, roots appear to have different mechanisms of gravitropism compared to stems and hypocotyls. Time course of curvature studies with light-grown seedlings were performed in the presence of latrunculin B (Lat-B), an actin-depolymerizing drug. Lat-B promoted gravitropic curvature in hypocotyls of both the WT and arc6 but had little or no effect on gravitropism in roots of both strains. These results suggest that F-actin is not required for hypocotyl gravitropism.

Journal Article↗

PubMed2005

Gravitational tractor for towing asteroids.

We present a design concept for a spacecraft that can controllably alter the trajectory of an Earth-threatening asteroid by using gravity as a towline. The spacecraft hovers near the asteroid, with its thrusters angled outwards so that the exhaust does not impinge on the surface. This proposed deflection method is insensitive to the structure, surface properties and rotation state of the asteroid.

Journal Article↗

PubMed2003

Microgravity alters respiratory sinus arrhythmia and short-term heart rate variability in humans.

We studied heart rate (HR), heart rate variability (HRV), and respiratory sinus arrhythmia (RSA) in four male subjects before, during, and after 16 days of spaceflight. The electrocardiogram and respiration were recorded during two periods of 4 min controlled breathing at 7.5 and 15 breaths/min in standing and supine postures on the ground and in microgravity. Low (LF)- and high (HF)-frequency components of the short-term HRV (< or =3 min) were computed through Fourier spectral analysis of the R-R intervals. Early in microgravity, HR was decreased compared with both standing and supine positions and had returned to the supine value by the end of the flight. In microgravity, overall variability, the LF-to-HF ratio, and RSA amplitude and phase were similar to preflight supine values. Immediately postflight, HR increased by approximately 15% and remained elevated 15 days after landing. LF/HF was increased, suggesting an increased sympathetic control of HR standing. The overall variability and RSA amplitude in supine decreased postflight, suggesting that vagal tone decreased, which coupled with the decrease in RSA phase shift suggests that this was the result of an adaptation of autonomic control of HR to microgravity. In addition, these alterations persisted for at least 15 days after return to normal gravity (1G).

Adult↗