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PubMed2004

Exposure of animals to artificial gravity conditions leads to the alteration of the glutamate release from rat cerebral hemispheres nerve terminals.

The biochemical basis underlying the effects of altered gravity on the process of nervous signal transmission is not clear. We have investigated the effect of hypergravity stress (created by centrifugation of rats at l0 g for 1 h) on the basal and stimulated release of L-[14C]glutamate (a chemical transmitter of excitatory signals) from isolated rat brain nerve terminals (synaptosomes). It has been shown that the hypergravity stress exerted a different influence on the Ca(2+)-dependent and the Ca(2+)-independent component of neurotransmitter release. The Ca(2+)-dependent L-[14C]glutamate release evoked by potassium chloride was equal to 14.4 +/- 0.7% of total synaptosomal label for control animals and 6.2 +/- 1.9% for animals, exposed to hypergravity (P < or = 0.05) and was more than twice decreased as a result of the hypergravity stress. We observed no statistically significant difference in the Ca(2+)-independent component of L-[14C]glutamate release. For control group and animals exposed to the hypergravity stress it was equal to 7.7 +/- 2.8% and 12.9 +/- 2.0%, respectively. We have also investigated the effect of the hypergravity stress on the activity of high-affinity Na(+)-dependent glutamate transporters. Km and Vmax of L-[14C]glutamate uptake have been determined. The maximal velocity of glutamate uptake was decreased as a result of hypergravity loading, but no difference in the Km values between control rats and hypergravity exposed animals was observed. These findings indicate that hypergravity stress alters neurotransmitter reuptake and exocytotic neurotransmitter release processes.

Animals↗

PubMed2005

Preparation and characterization of uniform nanosized cephradine by combination of reactive precipitation and liquid anti-solvent precipitation under high gravity environment.

In this work, a novel direct method, which was combined with reactive precipitation and liquid anti-solvent precipitation under high gravity environment, had been developed to prepare nanosized cephradine with narrow particle size distribution. Compared with commercial crude cephradine, the prepared cephradine showed a significant decrease in particle size, a significant increase in the specific surface area and shorter dissolving time when used for injection. The characteristic particle size was between 200-400 nm. The specific surface area increased from 2.95 to 10.87 m2/g after micronization. When the amount of L-arginin decreased from 0.25 to 0.18 g, the mixture of nanosized cephradine and L-arginine could still dissolve in 1 min. The X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that the physical characteristics and molecular states remained unchanged after the recrystallization process. This method had potential application in industrial fields because of its low cost, efficient processing and the ease of scaling-up.

Cephalosporins↗

PubMed2006

Production of salbutamol sulfate for inhalation by high-gravity controlled antisolvent precipitation.

The purpose of this study was to produce salbutamol sulfate (SS) as a model anti-asthmatic drug using high-gravity controlled precipitation (HGCP) through antisolvent crystallisation. An aqueous solution of SS was passed through a HGCP reactor with isopropanol as antisolvent to induce precipitation. Spray drying was employed to obtain dry powders. Scanning electron microscopy, X-ray powder diffraction (XRD), density measurement, thermal gravimetric analysis, and dynamic vapour sorption were carried out to characterise the powder physical properties. The aerosol performance of the powders was measured using an Aeroliser connected to a multiple stage liquid impinger operating at 60 L/min. The HGCP SS particles were elongated with 0.1 microm in width but varying length of several mum, which formed spherical agglomerates when spray dried. The particles showed the same XRD pattern and true density (1.3g/cm3) as the raw material, indicating that they belonged to the same crystalline form. However, the spray dried agglomerates had a much lower tapped density (0.1g/cm3) than the raw material (0.6g/cm3). Compared with the powder obtained by spray drying directly from an aqueous solution, the SS powders obtained from HGCP were much less hygroscopic (0.6% versus 10% water uptake at 90% RH). The in vitro aerosol performance showed a fine particle fraction FPFloaded and FPFemitted up to 54.5+/-4.9% and 71.3+/-10.0%, respectively. In conclusion, SS powder with suitable physical and aerosol properties can be obtained through antisolvent HGCP followed by spray drying.

Aerosols↗

PubMed2004

Continuous ethanol production and evaluation of yeast cell lysis and viability loss under very high gravity medium conditions.

A combined bioreactor system, composed of a stirred tank and a three-stage tubular bioreactor in series and with a total working volume of 3260 ml, was established. Continuous ethanol production was carried out using Saccharomyces cerevisiae and a very high gravity (VHG) medium containing 280 g l(-1) glucose. An average ethanol concentration of 124.6 g l(-1) or 15.8% (v) was produced when the bioreactor system was operated at a dilution rate of 0.012 h(-1). The yield of ethanol to glucose consumed was calculated to be 0.484 or 94.7% of its theoretical value of 0.511 when ethanol entrapped in the exhaust gas was incorporated. Meanwhile, quasi-steady states and non-steady oscillations were observed for residual glucose, ethanol and biomass concentrations for all of these bioreactors during their operations. Models that can be used to predict yeast cell lysis and viability loss were developed.

Biomass↗

PubMed2005

Treatment of lead mine waste by a Mozley multi-gravity separator (MGS).

Increasing environmental awareness and pressure is focusing attention on metal removal leading to the accelerated development of contaminated land reclamation technologies. The majority of wastes associated with base metal mining activity are fine tailings. Depending on the age and history of the metals, their characteristics vary considerably and each deposit requires individual characterisation. This paper investigates the treatment of lead-zinc mine wastes by the multi-gravity separator, a novel mineral processing machine. A laboratory study was carried out to find the most effective conditions using parameters such as drum angle and size fraction. A material and mass balance for the laboratory system has demonstrated that approximately 12% of the Pb can be removed in the form of concentrate with 12% Pb content.

Decontamination↗

PubMed2005

Two enhancements of the gravity algorithm for multiple spike train analysis.

The gravity method for neuronal assembly analysis represents each neuron as a particle in N-space with a time varying charge that is a filtered version of the corresponding spike train, with appropriate rules for forces between and movements of the charged particles. Resulting trajectories reflect neuronal timing relationships. The usual short time constants in the filter restrict aggregation to highly synchronized neurons and reduce the sensitivity for delayed correlations; long time constants in the filter reduce selectivity. Here we describe an enhancement that modifies rules for assigning charge increment times to allow mixtures of short and long lag correlations. Charge increments for each pair are offset from the actual spike times by time lags defined by features in corresponding cross-correlograms; no such charge offsets are invoked if the correlogram is flat. Tuning increases charge products and aggregation of long lag correlated pairs. A second enhancement uses a new three-dimensional display of particle pair trajectories to parse the type of neuronal relationship. For each pair, we record and display the inter-particle distance and the distance each particle moves from its original location in the N-space. The resulting trajectories cluster according to the type of interaction between the represented neurons. Results from simulated networks and in vivo multi-site recordings show that these modifications detect assembly properties not identified by the standard methods.

Action Potentials↗

PubMed2006

Influence of pitch tilts on the perception of gravity-referenced eye level in labyrinthine defective subjects.

We investigate the role of vestibular information in judging the gravity-referenced eye level (i.e., earth-referenced horizon or GREL) during sagittal body tilt whilst seated. Ten bilateral labyrinthine-defective subjects (LDS) and 10 age-matched controls set a luminous dot to their perception of GREL in darkness, with and without arm pointing. Although judgements were linearly influenced by the magnitude of whole-body tilt, results showed no significant difference between LDS and age-matched controls in the subjective GREL accuracy or in the intra-subject variability of judgement. However, LDS performance without arm pointing was related to the degree of vestibular compensation inferred from another postural study performed with the same patients. LDS did not utilize upper limb input during arm pointing movements as a source of graviceptive information to compensate for the vestibular loss. The data suggest that vestibular cues are not of prime importance in GREL estimates in static conditions. The absence of difference between controls and LDS GREL performance, and the correlation between the postural task and GREL accuracy, indicate that somatosensory input may convey as much graviceptive information required for GREL judgements as the vestibular system.

Adult↗

PubMed2005

Sulfide-iron interactions in domestic wastewater from a gravity sewer.

Interactions between iron and sulfide in domestic wastewater from a gravity sewer were investigated with particular emphasis on redox cycling of iron and iron sulfide formation. The concentration ranges of iron and total sulfide in the experiments were 0.4-5.4mgFeL(-1) and 0-5.1mgSL(-1), respectively. During anaerobic conditions, iron reduction kinetics were investigated and reduction rates amounted on average to 1.32mgFeL(-1)d(-1). Despite the very low solubility of iron sulfide, the reduced iron reacted only partly with sulfide to produce iron sulfide, even when dissolved sulfide was in excess. When a ferric chloride solution was added to sulfide containing anaerobic wastewater, the ferric iron was quickly reduced to ferrous forms by oxidation of dissolved sulfide and the ferrous iron precipitated almost completely as iron sulfide. During aerobic conditions, iron sulfide was oxidized with a half-life period of 11.7h. The oxidation rate of iron sulfide was significantly lower than that reported for the oxidation of dissolved sulfide.

Bioreactors↗

PubMed2001

[Pheochromocytoma in Africa: rarity, gravity and ectopy].

Pheochromocytoma is one of the main curable etiologies of high blood pressure, although its diagnosis and therapeutic management can be problematical: an incorrect diagnosis or inappropriate treatment may lead to fatal complications. This disease was exceptionally uncommon in the 1950s, and 30 years later about 30 cases had been reported; however, since 1981 there has been a progressive increase in the incidence of pheochromocytoma (48 documented cases in Africa). In Africa, this disease has two particular characteristics: the gravity of the clinical symptoms, mainly due to the physiological and pharmacological effects of catecholamines which as a result of this disease are stored and liberated at very high rates; and the ectopic site in a number of cases. To facilitate the diagnosis of pheochromocytoma improved clinical investigation is therefore advocated, but the necessary medical equipment is not always available in Africa. On this continent, the ectopic factor confirms the observations made in the early 1980s, and should be taken into consideration in the diagnosis and management of this disease.

Adolescent↗

PubMed1997

Stable magnetic field gradient levitation of Xenopus laevis: toward low-gravity simulation.

We have levitated, for the first time, living biological specimens, embryos of the frog Xenopus laevis, using a large inhomogeneous magnetic field. The magnetic field/field gradient product required for levitation was 1430 kG2/cm, consistent with the embryo's susceptibility being dominated by the diamagnetism of water and protein. We show that unlike any other earth-based technique, magnetic field gradient levitation of embryos reduces the body forces and gravity-induced stresses on them. We discuss the use of large inhomogeneous magnetic fields as a probe for gravitationally sensitive phenomena in biological specimens.

Animals↗

PubMed2000

Impact severity in self-initiated sits and falls associates with center-of-gravity excursion during descent.

Although the energy available during a fall from standing greatly exceeds that required to produce hip fracture, this occurs in only about 2% of falls in the elderly. This is thought to be due in part to one's ability to reduce the vertical impact velocity (nu(nu)) and kinetic energy (KE(nu)) of the body through energy absorption in the lower extremity muscles during descent. The present study tested the hypothesis that the magnitude and percent attenuation in nu(nu) and KE(nu) associate with the horizontal and vertical excursion of the body's center-of-gravity during descent. Measures were acquired of whole-body kinematics and lower extremity kinetics as young subjects underwent backward descents involving vertical drops of either thigh length (SIT) or lower extremity length (FALL), and horizontal pelvis excursions of either 33 or 66% of lower extremity length. In all trials, subjects attempted to "land as softly as possible." While attenuation in nu(nu) and KE(nu) (which averaged 62 and 92% respectively), did not associate with trial type, raw magnitudes of these parameters did, with nu(nu) averaging 2-fold greater, and KE(nu) averaging 6-fold greater, in 66% FALL than in 33% SIT or 66% SIT trials. This was due to a rapid increase in downward velocity accompanying the final stage of descent in 66% SIT and 66% FALL trials, which coincided with the knee moving posterior to the ankle. Accordingly, severe impacts likely accompany not only large fall heights, but also falls where the feet are thrown rapidly forward, as during a backward slip.

Accidental Falls↗

PubMedDate not supplied

Estimating the centre of gravity of the body on the basis of the centre of pressure in standing posture.

This study proposes to estimate the horizontal positions of the body's centre of gravity (CoG) in a standing posture, on the basis of the horizontal positions of the centre of pressure (CoP). The latter were measured with a force plate, and using a low-pass filter defined by a mathematical relationship of the relative magnitude of the CoG with respect to the magnitude of the CoP, as a function of the frequency oscillations (Brenière, 1996, Journal of Motor Behaviour 28, 291-298). This relationship was computed from the angular momentum equation applied to the whole body with respect to the CoG using the inverse dynamics approach and force plate recordings, and considering the CoP and CoG oscillations as simple periodic functions. Five subjects were asked to perform voluntary oscillations along medio-lateral and antero-posterior axes, keeping their bodies straight, and without moving their feet. The CoG accelerations measured by the force plate were compared with the CoG accelerations derived from the estimated CoG positions. The average root-mean-square difference between these accelerations was very small, confirming the accuracy of this method. This simplified way to calculate the CoG positions, rarely measured in standing, allows a comparative assessment of motion performance. This method could also be applied to other kinds of movement such as walking.

Acceleration↗

PubMed1988

Comparison of the chromatographic properties of sterols, select additional steroids and triterpenoids: gravity-flow column liquid chromatography, thin-layer chromatography, gas-liquid chromatography and high-performance liquid chromatography.

The chromatographic properties of approximately 100 sterols, select steroids of plant origin (sapogenins and steroidal alkaloids) and triterpenoids has been evaluated in this laboratory by monitoring their elution characteristics in adsorption (gravity column and thin-layer methods with and without the addition of silver nitrates), gas and reversed-phase high-performance liquid chromatography. The utility of each methodology to act in one or another chromatographic mode-separation, radio-chemical purification, quantitation and structural elucidation, is discussed. The importance of the tilt of the -OH group at C-3 as well as the polarity, size, an shape of the rest of the molecule as it effects the hydrogen-bonding ability of the -OH group is demonstrated through changes in chromatographic behavior that result from the step-wise introduction of double bonds, methyl, bromo, oxygen, nitrogen and cyclopropyl groups into 5 alpha-cholestanol. An independent aid in the structure identification and quantitation of the compounds was use of a multiple-wavelength diode array detector in which different wavelengths of the UV spectrum (200-400 nm) were simultaneously monitored following passage of the sample through a reversed-phase C18 column.

Chromatography, Gas↗

PubMed2003

Gravity and light effects on the circadian clock of a desert beetle, Trigonoscelis gigas.

Circadian function is affected by exposure to altered ambient force environments. Under non-earth gravitational fields, both basic features of circadian rhythms and the expression of the clock responsible for these rhythms are altered. We examined the activity rhythm of the tenebrionid beetle, Trigonoscelis gigas, in conditions of microgravity (microG; spaceflight), earth's gravity (1 G) and 2 G (centrifugation). Data were recorded under a light-dark cycle (LD), constant light (LL), and constant darkness (DD). Free-running period (tau) was significantly affected by both the gravitational field and ambient light intensity. In DD, tau was longer under 2 G than under either 1 G or microG. In addition, tauLL was significantly different from tauDD under microG and 1 G, but not under 2 G.

Animals↗

PubMed1990

Controlled inversion therapy: an adjunct to the elimination of gravity-dependent fragments following extracorporeal shock wave lithotripsy.

The retention of passable stone debris is the primary shortcoming of extracorporeal shock wave lithotripsy. Residual stone debris is located almost universally in gravity-dependent caudal calices. Our findings suggest that multiple sessions of controlled inversion therapy could have a beneficial role in the postoperative management of this select group of patients.

Fluid Therapy↗

PubMed1997

Effect of gravity on lung exhaled nitric oxide at rest and during exercise.

Exhaled nitric oxide (NO) from the lungs (VNO) in nose-clipped subjects increases during exercise. This may be due to endothelial shear stress secondary to changes in pulmonary blood flow. We measured VNO after modifying pulmonary blood flow with head-out water immersion (WI) or increased gravity (2 Gz) at rest and during exercise. Ten sedentary males were studied during exercise performed in air and WI. Nine subjects were studied at 1 and 2 Gz. Resting NO concentrations in exhaled air ([NO]) were 16.3 +/- 8.2 ppb (air). 15 +/- 8.2 ppb (WI) and 17.4 +/- 5 ppb (2 Gz). VNO (ppb/min) was calculated as [NO]VE and was unchanged at rest by either WI or 2 Gz. VNO increased linearly with Vo2, VE and fii during exercise in air, WI and at 2 Gz. These relationships did not differ among the experimental conditions. Therefore, changes in pulmonary blood flow failed to alter the output of NO exhaled from the lungs at rest or during exercise.

Adult↗

PubMed1997

Preoperative and postoperative magnetic resonance imaging (MRI) findings of radiculomeningeal arteriovenous malformations: important role of gravity in the symptoms and MRI.

BACKGROUND: The symptoms of radiculomeningeal arteriovenous malformations (AVMs) are reported to be uniform, which suggests it to be a conus medullaris syndrome, and in fact, the lesions on magnetic resonance imaging (MRI) images usually include the conus medullaris. However, the reason why the conus medullaris is always involved in the lesion has not been discussed. METHODS: We encountered seven patients with spinal radiculomeningeal AVMs and operated on all of them. We evaluated the preoperative and postoperative MRI findings in these patients. Postoperative MRI was followed ranging from 6-32 months (mean: 21 months) after surgery. RESULTS: All of our patients showed swelling of the spinal cord, including the conus medullaris, on the preoperative magnetic resonance image. Postoperatively, MRI showed that the swelling of the spinal cord had resolved but that it had finally deteriorated into an atrophic condition. In all of five patients who could be followed up using multiple postoperative MRI scans, sequential T2-weighted images showed that the most rostral level of areas with increased signal in the spinal cord moved in a caudal direction with time. CONCLUSIONS: This and the fact that the conus medullaris was included in the swelling of the spinal cord regardless of the level of the nidus in all our patients, suggested that gravity played an important role in the etiology of radiculomen-ingeal AVM in these patients.

Aged↗

PubMed2004

Gravity spinning of polycaprolactone fibres for applications in tissue engineering.

Poly(epsilon-caprolactone) (PCL) fibres have been produced by wet spinning from solutions in acetone under low shear (gravity flow) conditions. The tensile strength and stiffness of as-spun fibres were highly dependent on the concentration of the spinning solution. Use of a 6% w/v solution resulted in fibres having strength and stiffness of 1.8 MPa and 0.01 GPa, respectively, whereas these values increased to 9.9 MPa and 0.1 GPa when fibres were produced from 20% w/v solutions. Cold drawing to an extension of 500% resulted in further increases in fibre strength (up to 50 MPa) and stiffness (0.3 GPa). The surface morphology of as-spun fibres was modified, to yield a directional grooved pattern by drying in contact with a mandrel having a machined topography characterised by a peak-peak separation of 91 microm and a peak height of 30 microm. Limited in vitro studies of cell behaviour in contact with the fibres were performed using cell culture. The number of attached fibroblasts and myoblasts on as-spun PCL fibres after 5 days in cell culture was lower than on tissue culture plastic by a factor 2 and 1.5, respectively, but higher than on Dacron monofilament by a factor of 4 and 11, respectively. The high fibre compliance and the potential for controlling the fibre surface architecture to promote contact guidance effects together with the maintained proliferation of fibroblasts and myoblasts on as-spun PCL fibres in vitro recommends their use for 3-D scaffold production in soft tissue engineering.

Animals↗