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Results for “Gravity, Altered”

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PubMed1998

Microgravity and its implication for fermentation biotechnology.

Fermentation processes are highly dependent upon physical and chemical environmental parameters, many of which are influenced by gravity. Extending biotechnology into the realm of space flight provides researchers with an opportunity to investigate the role that gravity plays in natural growth processes. Physical factors governing cell sedimentation, nutrient mixing and byproduct dispersion are altered in the absence of the constant sedimenting force of gravity. In addition, space flight has also been shown to give rise to a wide variety of indirect consequences associated with the physiology of the organisms themselves.

Bacterial Physiological Phenomena↗

PubMed2005

Simulated hypogravity impairs the angiogenic response of endothelium by up-regulating apoptotic signals.

Health hazards in astronauts are represented by cardiovascular problems and impaired bone healing. These disturbances are characterized by a common event, the loss of function by vascular endothelium, leading to impaired angiogenesis. We investigated whether the exposure of cultured endothelial cells to hypogravity condition could affect their behaviour in terms of functional activity, biochemical responses, morphology, and gene expression. Simulated hypogravity conditions for 72 h produced a reduction of cell number. Genomic analysis of endothelial cells exposed to hypogravity revealed that proapoptotic signals increased, while antiapoptotic and proliferation/survival genes were down-regulated by modelled low gravity. Activation of apoptosis was accompanied by morphological changes with mitochondrial disassembly and organelles/cytoplasmic NAD(P)H redistribution, as evidenced by autofluorescence analysis. In this condition cells were not able to respond to angiogenic stimuli in terms of migration and proliferation. Our study documents functional, morphological, and transcription alterations in vascular endothelium exposed to simulated low gravity conditions, thus providing insights on the occurrence of vascular tissue dysregulation in crewmen during prolonged space flights. Moreover, the alteration of vascular endothelium can intervene as a concause in other systemic effects, like bone remodelling, observed in weightlessness.

Animals↗

PubMed1984

Selected physical and chemical characteristics of prostatic fluid collected by ejaculation from healthy dogs and from dogs with bacterial prostatitis.

Forty specimens of prostatic fluid, collected by ejaculation from 36 dogs with bacterial prostatitis, and 43 specimens of prostatic fluid collected by the same method from 42 healthy dogs were analyzed with respect to pH, specific gravity, cholesterol concentration, and zinc, copper, iron, calcium, and magnesium concentrations. Values from prostatic fluid of infected dogs were compared with values from prostatic fluid of healthy dogs, using a variety of statistical methods. In striking contrast to data obtained from human beings, prostatic fluid pH, specific gravity, or cholesterol zinc concentrations were not altered in dogs with bacterial prostatitis. Seemingly, these tests are not reliable in the diagnosis of bacterial prostatitis in dogs.

Animals↗

PubMed2002

Lateral relocation of auxin efflux regulator PIN3 mediates tropism in Arabidopsis.

Long-standing models propose that plant growth responses to light or gravity are mediated by asymmetric distribution of the phytohormone auxin. Physiological studies implicated a specific transport system that relocates auxin laterally, thereby effecting differential growth; however, neither the molecular components of this system nor the cellular mechanism of auxin redistribution on light or gravity perception have been identified. Here, we show that auxin accumulates asymmetrically during differential growth in an efflux-dependent manner. Mutations in the Arabidopsis gene PIN3, a regulator of auxin efflux, alter differential growth. PIN3 is expressed in gravity-sensing tissues, with PIN3 protein accumulating predominantly at the lateral cell surface. PIN3 localizes to the plasma membrane and to vesicles that cycle in an actin-dependent manner. In the root columella, PIN3 is positioned symmetrically at the plasma membrane but rapidly relocalizes laterally on gravity stimulation. Our data indicate that PIN3 is a component of the lateral auxin transport system regulating tropic growth. In addition, actin-dependent relocalization of PIN3 in response to gravity provides a mechanism for redirecting auxin flux to trigger asymmetric growth.

Arabidopsis↗

PubMed2002

Gravity: It's the law.

Based on experience in microgravity and on centrifuge induced hypergravity, exposure to either altered force field causes marked effects in animals and humans. It would seem logical that changes from unit gravity would have different effects depending on whether gravity is increased or decreased. Examples will be presented of responses to altered gravitational fields and changes in human and animal musculoskeletal, cardiopulmonary neurovestibular and metabolic responses.

Journal Article↗

PubMed1995

Brain edema and neurologic status with rapid infusion of 0.9% saline or 5% dextrose after head trauma.

We previously reported that intravenous (i.v.) administration of large volumes (0.2 ml/g) of either an isotonic dextrose-free solution or 5% dextrose solution given over 18 h after closed head trauma (CHT) in rats did not significantly affect neurological severity score or brain tissue specific gravity. However, it is possible that with more rapid administration, isotonic or 5% dextrose i.v. solutions may alter neurological outcome after CHT. Our study examined whether neurological severity score, brain tissue specific gravity and water content, and blood composition were significantly altered when 0.25 ml/g of either 0.9% saline or 5% dextrose was given i.v. over 0.5 h (rather than over 18 h) after CHT. Eight-four rats that survived ether anesthesia and CHT were randomly assigned to one of 11 experimental groups. Saline- and dextrose-treated rats were evaluated at 4 and 48 h after CHT and were compared to rats without CHT and to untreated rats at 4 and 48 h after CHT. There were no statistically significant differences in neurologic outcome and brain edema between the untreated and the saline-treated groups. However, 5% dextrose i.v. increased mortality (group 6 and 11, 50 and 0% survivors, respectively), decreased specific gravity in the noncontused hemisphere, and worsened neurologic outcome with and without CHT. Blood osmolality remained stable in comparison to the baseline value of 291.9 +/- 7.4 mOsm/kg (mean +/- SD).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2006

Establishment of stable human fibroblast cell lines constitutively expressing active Rho-GTPases.

Small GTP-binding proteins of the Rho family (RhoA, Cdc42, Rac1) regulate the organisation and the turnover of the cell's cytoskeleton and adhesion structures. A significant function of these cellular structures is to translate and counterbalance forces applied to, or generated by, cells in order to maintain homeostasis and control cell movement. We therefore hypothesised that Rho-GTPases are directly involved in cellular gravity perception and may participate in the alterations induced in microgravity. To define an adequate cellular model allowing to investigate this issue, we have established stable cell lines constitutively expressing active forms of either RhoA, Cdc42, or Rac1. The three cell lines differ by morphology and by their ability to form filopodia, lamellipodia, and bundles of actin stress fibers. Overexpression of the active form of either RhoA, Cdc42, or Rac1 is compatible with cell viability and does not affect cell population doubling time. Thus, our series of mutant cells appear well suited to gain further knowledge on the molecular mechanisms of cellular gravity perception.

Actin Cytoskeleton↗

PubMed1998

Changes in lower limb volume in humans during parabolic flight.

Variations in gravity [head-to-foot acceleration (Gz)] induce hemodynamic alterations as a consequence of changes in hydrostatic pressure gradients. To estimate the contribution of the lower limbs to blood pooling or shifting during the different gravity phases of a parabolic flight, we measured instantaneous thigh and calf girths by using strain-gauge plethysmography in five healthy volunteers. From these circumferential measurements, segmental leg volumes were calculated at 1, 1.7, and 0 Gz. During hypergravity, leg segment volumes increased by 0.9% for the thigh (P < 0.001) and 0.5% for the calf (P < 0.001) relative to 1-Gz conditions. After sudden exposure to microgravity following hypergravity, leg segment volumes were reduced by 3.5% for the thigh (P < 0.001) and 2.5% for the calf (P < 0.001) relative to 1.7-Gz conditions. Changes were more pronounced at the upper part of the leg. Extrapolation to the whole lower limb yielded an estimated 60-ml increase in leg volume at the end of the hypergravity phase and a subsequent 225-ml decrease during microgravity. Although quantitatively less than previous estimations, these blood shifts may participate in the hemodynamic alterations observed during hypergravity and weightlessness.

Adult↗

PubMed1987

Effect of body position on intraocular pressure and aqueous flow.

The relationship between intraocular pressure and the rate of aqueous humor formation was studied in human subjects. Intraocular pressure was altered by changing the subject's gravity-dependent body position. Aqueous humor flow was measured fluorophotometrically. An average change of intraocular pressure of 2.4 +/- 1.2 mmHg and 11.2 +/- 2.7 mmHg was recorded in subjects whose body position was alternated +/- 15 degrees from horizontal and +/- 50 degrees from horizontal. No change of the rate of fluorescein clearance was observed for the milder change of position. A small change of fluorescein clearance was noted in response to the steeper change of position. Changing intraocular pressure seems not to induce compensatory changes in aqueous flow. Therefore we conclude that aqueous formation is relatively pressure-insensitive, a conclusion one would draw from clinical instances of angle-closure glaucoma or as in other systems of secretion, such as the toad bladder or the cerebrospinal fluid, where alterations in pressure do not necessarily influence flow. If there is a regulator of aqueous flow it is not responsive to the changes in intraocular pressure brought about in this study. If aqueous flow regulates intraocular pressure or compensates for changes in intraocular pressure, the signal is not small changes in pressure.

Adolescent↗

PubMed2000

The effects of hypergravity and substrate vibration on vestibular function in developing chickens.

We used linear vestibular evoked potentials (VsEPs) to characterize peripheral and central vestibular function in birds following embryogenesis at 2G centrifugation or at elevated levels of vibration (+20dB re: background levels). Additionally, we characterized peripheral and central vestibular adaptation to 2G centrifugation in early post-hatch birds. Linear VsEP response peak latencies, amplitudes, thresholds and input/output functions were quantified and compared between experimental and control animals. Birds vibrated throughout embryogenesis and up to one-week post-hatch revealed no changes in linear VsEP response components compared to control siblings. Birds centrifuged at 2G throughout embryogenesis also evidenced no changes in the linear VsEP measured at hatch (P0). Significant changes were seen, however, for linear VsEPs of post-hatch birds placed at 2G for 7 days beginning on post-hatch day 5. Linear VsEPs for these animals displayed significant reductions in response amplitudes associated with peaks P2, N2 and P3, response peaks generated by central neural relays of gravity receptors. The earliest response components, generated by the peripheral vestibular nerve (i.e., P1, N1), were not significantly altered with the 7-day exposure to 2G. Thus, there was no evidence of generalized changes in peripheral gravity receptor excitability or in the rate of maturation in developing animals under increased levels of gravity or vibration. If gravity level plays a critical role in shaping peripheral vestibular ontogeny at magnitudes between 1 and 2G, then it may serve to stabilize function under changing G-fields or it may operate on physiological features that can not be resolved by the VsEP. In contrast, exposure to elevated gravity during post-hatch periods does alter central vestibular function thus providing direct evidence for central vestibular adaptation to the gravitational environment. The fact that central functional change was observed in hatchlings and not embryos, raises the possibility that the first 2-weeks post-hatch may be a critical period of "heightened developmental sensitivity" to hypergravity.

Adaptation, Physiological↗

PubMed1992

The significance of immunosuppression and hormonal alteration in neurotraumatology.

Thirty head trauma patients receiving no steroid treatment were investigated for a period of 20 days. The patients were divided into three groups according to their Glasgow Coma Scale (GCS) scores: GCS = 4-8 and GCS = 9-13. We studied their immunological and hormonal status with special reference to the relationship among severity of trauma, immunosuppression and hormonal alteration. The immunity tests included lymphocyte transformation, lymphocyte phenotyping and delayed hypersensitivity (DH) skin tests. The hormone study consisted of serum cortisol and ACTH level determinations. The following results were obtained: (1) The entire group suffered from significant suppression in lymphocyte responses to mitogens PHA and Con A on day 1 and day 10 after injury, but later they improved; (2) There was a significant fall (P less than 0.05) in OKT3 OKT4 and active T-cell on day 10, especially in patients with GCS less than or equal to 8; (3) A significant increase in OKT8 and decrease in OKT4 was concurrently noted causing an inversion in the ratio of OKT4 to OKT8 on the 10th day (patients 0.96:1, normal 1.6:1, P less than 0.01); (4) No significant change was observed in the number of B-cells, suggesting that cell-mediated immunity may be affected earlier and more severely than antibody producing capacity; (5) Delayed hypersensitivity skin test showed a high incidence of anergy in the severe (GCS less than or equal to 8) and fetal cases. A high mortality in anergic cases was also noted; (6) Elevated ACTH and cortisol levels detected upon arrival rapidly declined to normal value at day 5. In addition, we found no correlation between the curve of serum ACTH and cortisol alteration and the biphasic suppression curve of lymphocyte transformation in later study period. These findings suggest that the severity of natural resistance impairment seems to be related to the gravity of clinical manifestations and to the serum hormonal alteration only in the initial stages. Also, we find that the development of anergy may be an index of poor prognosis.

Adrenocorticotropic Hormone↗

PubMed2025

Twisted Sister1: an agravitropic mutant of bread wheat (Triticum aestivum) with altered root and shoot architectures.

We identified a mutant of hexaploid wheat (Triticum aestivum) with impaired responses to gravity. The mutant, named Twisted Sister1 (TS1), had agravitropic roots that were often twisted along with altered shoot phenotypes. Roots of TS1 were insensitive to externally applied auxin, with the genetics and physiology suggestive of a mutated AUX/IAA transcription factor gene. Hexaploid wheat possesses over 80 AUX/IAA genes, and sequence information did not identify an obvious candidate. Bulked segregant analysis of an F2 population mapped the mutation to chromosome 5A, and subsequent mapping located the mutation to a 41 Mbp region. RNA-seq identified the TraesCS5A03G0149800 gene encoding a TaAUX/IAA protein to be mutated in the highly conserved domain II motif. We confirmed TraesCS5A03G0149800 as underlying the mutant phenotype by generating transgenic Arabidopsis thaliana. Analysis of RNA-seq data suggested broad similarities between Arabidopsis and wheat for the role of AUX/IAA genes in gravity responses, although there were marked differences. Here we show that the sequenced wheat genome, along with previous knowledge of the physiology of gravity responses from other plant species, gene mapping, RNA-seq, and expression in Arabidopsis have enabled the cloning of a key wheat gene that defines plant architecture.

Triticum↗

PubMed2005

Loading effects on rat craniomandibular morphology: a system for gravity studies.

Gravity effects on muscle and bone are a major impediment to long-term space travel. We introduce a model for studying these effects, the craniomandibular system. Some advantages of this system include: (1) craniomandibular morphology is determined by epigenetic factors including gravity, (2) relatively light forces can significantly alter its morphology, and (3) soft diet and tooth loss produce effects that are similar to those produced in lower limbs by weightlessness. In the study, implants made either of gold (experimental group) or lightweight acrylic (controls) were attached to adult rats' mandibles. After 13 weeks, the animals' skulls and mandibles were dissected. Pair-wise comparisons indicated that the experimental animals showed significantly shortened and narrowed cranial bases, and significant changes in the posterior zygomatic arch region. These results indicate that simulated macrogravity influences bone remodeling in the adult craniomandibular system.

Acrylic Resins↗

PubMed2003

Electrophysiological properties of the utricular primary transducer are modified during development under hypergravity.

The electrophysiological development of hair cells between birth and the eight postnatal day (P8) was studied in the utricular macula of rats gestated in nest boxes mounted upon a centrifuge, subjecting the animals to a gravitational force of 2G. Whole-cell voltage-clamp recordings were made on cells in the acutely isolated epithelium. Cells were accessed through a tear in the epithelium, no enzymatic dissociation procedures were employed. Under artificially enhanced gravity, the whole cell conductance was dramatically altered in the two types of hair cells. Significant increases occurred from P3-4 in the type I cells while in the type II cells, the effect was delayed until P7-8. Fourfold and threefold increases of the mean slope conductance were observed at P7-8 in the type I and type II hair cells, respectively. These results indicate that the electrophysiological properties of a primary transducer such as utricle may be modified by variation of the primary stimulus during development.

Aging↗

PubMed1985

Ex vivo effects of nifedipine, nisoldipine and nitrendipine on filterability of red blood cells from healthy volunteers.

In a balanced, randomised and double-blind trial, the effects of single oral dose of nifedipine, nitrendipine and nisoldipine were compared with placebo in eight healthy volunteers. Red cell filterability, measured with a gravity driven filtration technique, was not significantly altered by any of the three calcium antagonists compared with placebo, when RBCs were filtered within 2 h of venepuncture. Storage of RBCs for 24 h at 25 degrees C, however, significantly reduced RBC filterability compared with 2 h (P less than 0.05), but the reduction after nifedipine and nitrendipine was significantly (P less than 0.05) less than after placebo. The above results demonstrate an effect of calcium antagonists on filterability of stored RBCs.

Adult↗

PubMedDate not supplied

Positional nystagmus in association with macroglobulinemia.

Summary--Waldenstrom's macroglobulinemia is a malignant lymphoproliferative disease associated with a monoclonal macroglobulinemia. Most explanations of the cochlear and vestibular symptoms in this disease have dealt with vascular thrombotic or hemorrhagic phenomena. Five patients currently being treated for macroglobulinemia have been reviewed. Three patients gave a history of periodic dizziness and underwent extensive neuro-otologic examination. The results suggestsed an alternate mechanism for the pathophysiology of the vestibular disturbance in macroglobulinemia. Vestibular examination by use of electronystagmography provided information which suggest that the cupulae may be altered by the macroglobulins to act as gravity receptors.

Adult↗

PubMed1994

Plasma osmolality and brain water content in a rat glioma model.

Little is known about how intravenous fluids influence peritumoral edema formation. This experiment was designed to determine, in a rat glioma model, whether changes in plasma osmolality alter water content, as assessed by specific gravity (SpGr), in normal and neoplastic cerebral tissue. Cells cultured from an ethylnitrosourea-induced rat glioma were stereotactically implanted into the right striatum of Fischer 344 rats. A tumor growth interval of 21 days was allowed. In a second experiment, rats underwent a 60-second cortical freeze injury followed by 24 hours' recovery. In both experiments, rats were assigned to one of three groups: hypotonic (100 ml/kg of 0.2 mol/L NaCl in H2O, intraperitoneally; resultant plasma osmolality approximately 268 mOsm/kg); isotonic (no treatment; plasma osmolality approximately 298 mOsm/kg); or hypertonic (10 ml/kg of 1.0 mol/L NaCl in H2O, intraperitoneally; plasma osmolality approximately 342 mOsm/kg). Thirty minutes after fluid injection, regional SpGr was determined using a kerosene-bromobenzene gradient. In subsets of rats, the tissue morphology and blood-brain barrier permeability of Evans blue dye were assessed. Tissue within the freeze lesion was stained by Evans blue dye with sharp demarcation. Evans blue dye did not stain gliomatous tissue, and central necrosis was not histologically evident. In isotonic rats, glioma SpGr was reduced (1.0411 +/- 0.0012 g/ml) relative to the contralateral striatum (1.0437 +/- 0.0008 g/ml; P < 0.001). Despite this, a strong linear relation was observed for SpGr and plasma osmolality in both neoplastic and normal tissue. Within the freeze lesion in isotonic rats, SpGr was severely reduced (1.0335 +/- 0.0008 g/ml; P < 0.0001) compared with contralateral frontal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2000

Myostatin and insulin-like growth factor-I and -II expression in the muscle of rats exposed to the microgravity environment of the NeuroLab space shuttle flight.

The mechanism of the loss of skeletal muscle mass that occurs during spaceflight is not well understood. Myostatin has been proposed as a negative modulator of muscle mass, and IGF-I and IGF-II are known positive regulators of muscle differentiation and growth. We investigated whether muscle loss associated with spaceflight is accompanied by increased levels of myostatin and a reduction in IGF-I and -II levels in the muscle, and whether these changes correlate with an increase in muscle proteolysis and apoptosis. Twelve male adult rats sent on the 17-day NASA STS-90 NeuroLab space flight were divided upon return to earth into two groups, and killed either 1 day later (R1) or after 13 days of acclimatization (R13). Ground-based control rats were maintained for the same periods in either vivarium (R3 and R15, respectively), or flight-simulated cages (R5 and R17, respectively). RNA and protein were isolated from the tibialis anterior, biceps femoris, quadriceps, and gastrocnemius muscles. Myostatin, IGF-I, IGF-II and proteasome 2c mRNA concentrations were determined by reverse transcription/PCR; myostatin and ubiquitin mRNA were also measured by Northern blot analysis; myostatin protein was estimated by immunohistochemistry; the apoptotic index and the release of 3-methylhistidine were determined respectively by the TUNEL assay and by HPLC. Muscle weights were 19-24% lower in the R1 rats compared with the control R3 and R5 rats, but were not significantly different after the recovery period. The myostatin/beta-actin mRNA ratios (means+/-s.e.m. ) were higher in the muscles of the R1 rats compared with the control R5 rats: 5.0-fold in tibialis (5.35 +/- 1.85 vs 1.07 +/- 0.26), 3.0-fold in biceps (2.46+/-0.70 vs 0.81 +/- 0.04), 1.9-fold in quadriceps (7.84 +/- 1.73 vs 4.08 +/- 0.52), and 2.2-fold in gastrocnemius (0.99 +/- 0.35 vs 0.44 +/- 0.17). These values also normalized upon acclimatization. Our antibody against a myostatin peptide was validated by detection of the recombinant human myostatin protein on Western blots, which also showed that myostatin immunostaining was increased in muscle sections from R1 rats, compared with control R3 rats, and normalized upon acclimatization. In contrast, IGF-II mRNA concentrations in the muscles from R1 rats were 64-89% lower than those in R3 animals. With the exception of the gastrocnemius, IGF-II was also decreased in R5 animals maintained in flight-simulated cages, and normalized upon acclimatization. The intramuscular IGF-I mRNA levels were not significantly different between the spaceflight rats and the controls. No increase was found in the proteolysis markers 3-methyl histidine, ubiquitin mRNA, and proteasome 2C mRNA. In conclusion, the loss of skeletal muscle mass that occurs during spaceflight is associated with increased myostatin mRNA and protein levels in the skeletal muscle, and a decrease in IGF-II mRNA levels. These alterations are normalized upon restoration of normal gravity and caging conditions. These data suggest that reciprocal changes in the expression of myostatin and IGF-II may contribute to the multifactorial pathophysiology of muscle atrophy that occurs during spaceflight.

Analysis of Variance↗