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At least 631 records · Page 35Linked to original sources
PubMed1995

[Density, specific gravity and baricity of various spinal anesthetics and those of normal human cerebrospinal fluid in Japanese].

We measured the density and specific gravity at room (20 degrees C) and body (37 degrees C) temperatures of spinal anesthetic solutions, which have been commercially prepared in Japan. Solutions investigated were; (1) 0.4 % and 0.5 % tetracaine (T) in water, 0.5 % T in normal saline, 5 % glucose and 10 % glucose, (2) 0.3 % dibucaine in 5 % sodium chloride: (P), (3) 0.24 % dibucaine with 0.12 % tetracaine in 9.5 % glucose: (N); (4) 3 % lidocaine in 8.5 % glucose: (X); and (5) 0.5 % bupivacaine in water containing preservatives: (M). We also determined the density and specific gravity of normal human cerebrospinal fluid (CSF) in Japanese (n = 10) at 37 degrees C. Each local anesthetic solution was classified into hyperbaric, isobaric or hypobaric solution. Thirty seven centigrade 0.5 % T in normal saline and 37 degrees C 0.5 % M in water had the density comparable to 37 degrees C human CSF and were considered to be relatively isobaric solutions. Our data demonstrated that human CSF had various densities. Therefore, it is possible that these isobaric solutions would vary their pharmacodynamic profiles in intrathecal use according to individual CSF characteristics and temperature of the solution.

Anesthesia, Spinal↗
PubMed1995

[Effects of altered gravity on the culture of unicellular eucaryotic organisms, Bursaria truncatella (Ciliophora)].

The paper reports the results of experiments with centrifugation and clinostating. Growth rate, cellular division and several morphofunctional characteristics of unicellular organisms of infusoria Bursaria truncatella in culture were studied under normal (1 g), elevated (hypergravity at 2 and 5 g), and compensated gravity. The data point to certain changes in the functional activity and morphology of cells consequent to long-time cultivation under these conditions. The observed regularities in the dynamics of B.truncatella growth and shifts in its physiology and morphology due to hypergravity or compensated gravity support our earlier proposed working hypothesis about the dominance of functional activity over morphological properties in sensitivity of unicellular organisms to perception and realization of the gravitational stimulus.

Animals↗
PubMed1976

[Urine specific gravity and osmolarity in hypertension patients with dehydration].

Results are reported from the comparative investigations of kidney concentration function by urine specific gravity and its osmolatity of 58 patients with arterial hypertension. Significant differences were found in more of the half of the patients. On the base of certain theoretical prerequisites and possibilities of technical errors was concluded that the determination of the maximal urine osmolality is a more reliable and more accurate index for the actual renal concentration ability. Urine specific gravity can be used in the everyday clinical practice due to the more convenient and easier determination. Urine osmolality must be used predominantly in scientific-clinical studies.

Adult↗
PubMed1985

Optic nerve dysfunction during gravity inversion. Pattern reversal visual evoked potentials.

The intraocular pressure (IOP) in humans approximately doubles when a head-down, or inverted, position is assumed. Simultaneously, the ophthalmic artery pressure increases by an even greater absolute magnitude. We recorded pattern reversal visual evoked potentials (PRVEPs) in 16 subjects in both the inverted and upright positions. In ten of the 16 subjects, we performed an additional experiment. On a different day, we obtained control PRVEPs, and then, using a scleral suction cup, we artificially increased the IOPs to the same values reached when the subjects were previously inverted. We found that the PRVEP amplitudes were significantly reduced in both experiments compared with corresponding control recordings, without changes in latency or wave form. Furthermore, the degree of amplitude reduction was even greater during gravity inversion than with suction cup elevation of IOP. The effects of IOP on optic nerve function as measured by the PRVEP appear to be dependent more on the IOP than on vascular perfusion. We also concluded that gravity inversion activities pose potential risks to the eyes.

Adult↗
PubMed1997

Effect of gravity and diffusion interface proximity on the morphology of collagen gels.

Collagen solutions (0.25% w/v) were polymerized in microgravity (STS-77, 10 days) along with simultaneous ground controls. Assembly conditions were achieved by the passage of buffer ions across a dialysis membrane into a reaction chamber containing the dissolved collagen. The gels were analyzed macroscopically and microscopically to assess the influence of gravity and the oriented diffusion of buffer ions on the resulting product. Double-blind rankings based on visual observation of the gels established that all of the flight gels (n = 8) were more uniform in appearance than all of the ground gels (n = 6). Photography using side illumination of the gels revealed the more granular appearance of the ground gels relative to the highly uniform appearance of the flight gels. Scanning electron microscopy established this difference at the microscopic level. Proximity to the dialysis interface and the presence or absence of gravity were both found to control the porosity and uniformity of the matrix.

Buffers↗
PubMed2004

Gravity-induced convective flow in microfluidic systems: electrochemical characterization and application to enzyme-linked immunosorbent assay tests.

A way of using gravity flow to induce a linear convection within a microfluidic system is presented. It is shown and mathematically supported that tilting a 1 cm long covered microchannel is enough to generate flow rates up to 1000 nL.min(-1), which represents a linear velocity of 2.4 mm.s(-1). This paper also presents a method to monitor the microfluidic events occurring in a covered microchannel when a difference of pressure is applied to force a solution to flow in said covered microchannel, thanks to electrodes inserted in the microfluidic device. Gravity-induced flow monitored electrochemically is applied to the performance of a parallel-microchannel enzyme-linked immunosorbent assay (ELISA) of the thyroid-stimulating hormone (TSH) with electrochemical detection. A simple method for generating and monitoring fluid flows is described, which can, for instance, be used for controlling parallel assays in microsystems.

Electricity↗
PubMed1982

Prolactin induces increase in the specific gravity of salamander, Hynobius retardatus, that raises adaptability to water.

The migration of the salamander, Hynobius retardatus, from land to water, which normally occurs in the breeding season, was induced by the injection of prolactin. The migration was accompanied by certain morphological changes (wider tail or swollen body); the observed morphological changes resembled those of salamanders collected from ponds during the breeding season. The prolactin-treated salamanders sank to the bottom of the water. In contrast, the control salamanders that did not receive prolactin floated near the water surface. The specific gravity of the whole body of the prolactin-treated animals was greater than unity. Prolactin injection induced a remarkable enlargement of the tissue between the skin and muscle, in which a considerable amount of mucopolysaccharide-rich substance accumulated. Because of the hydrophilic nature of the mucopolysaccharides, and increased mucopolysaccharide may absorb more water, which, in turn, may result in an increase of the osmotic pressure of the serum. This may eventually cause the animals to migrate from land to water to quench the "thirst." The absorption of water may make the specific gravity greater, and this allows the animals to sink in water.

Acclimatization↗
PubMed1988

Changes in center of gravity in boys with Duchenne muscular dystrophy.

A study was undertaken, using methods of stabilometry to compare stability of stance in normal children (n = 37) and those with Duchenne muscular dystrophy (n = 61). The purpose of this study was to monitor changes in the locus of the center of gravity and the range and frequency of sway and to evaluate the effect of orthotic application in an attempt to obtain information that would assist further development of orthoses. In group 1, boys with Duchenne muscular dystrophy who were still walking without assistance (mean age 7.2 +/- 1.76 years), the analysis of sway showed that, between 5 and 6 years of age, the boys already had ranges of anteroposterior (A/P) and lateral (Lat) sway that were significantly greater than those found in normal children (A/P P less than 0.05, Lat P less than 0.01). In group 2, boys with Duchenne muscular dystrophy when orthoses had been introduced (n = 23, mean age 10.4 +/- 1.47 years), the center of gravity was returned to a more normal position. There was a reduction of the anteroposterior range of sway, but the lateral range of sway remained significantly greater (P less than 0.01) as did the frequency of sway in both the anteroposterior and lateral directions (A/P P less than 0.001, Lat P less than 0.001).

Child↗
PubMed1993

Effects of development and altered gravity conditions on cytochrome oxidase activity in a vestibular nucleus of the larval teleost brain: a quantitative electronmicroscopical study.

The mitochondrial enzyme, cytochrome oxidase, was localized cytochemically in the nucleus magnocellularis, a primary relay nucleus of vestibular information within the area octavolateralis in the fish brain. Larvae of the cichlid fish Oreochromis mossambicus were analyzed at different developmental stages (4, 10, and 35 days post-hatching) and after long-term exposure (8 days) to increased gravity (2-4 g). Quantification of highly reactive, moderately reactive, and nonreactive mitochondria reveals differences in the cytochrome oxidase activity of various cellular structures, for example, perikarya of neurons, presynaptic terminals, and myelinated and nonmyelinated cell profiles. Cytochrome oxidase activity in the mitochondria of neuronal perikarya increases during development which parallels the differentiation of the area octavolateralis. This possibly reflects the increasing energy demand during maturation and innervation of the magnocellular nucleus. Hyper-g-exposure of the larvae for 8 days (centrifuge) caused a further augmentation of cytochrome oxidase activity in the perikarya within the nucleus magnocellularis. This may reflect an increased oxidative metabolism resulting from the need for compensation of altered inputs from gravity-sensitive epithelia in the inner ear. Another possibility is that acceleration within a centrifuge causes physiological stress for the animals and, therefore, influences the cytochrome oxidase activity in neurons.

Animals↗
PubMed2000

TNF-alpha-dependent activation of NF-kappa B in human osteoblastic HOS-TE85 cells is repressed in vector-averaged gravity using clinostat rotation.

Effects of vector-averaged gravity on tumor necrosis factor (TNF)-alpha-dependent activation of nuclear factor kappa B (NF-kappa B) in human osteoblastic HOS-TE85 cells were investigated by culturing the cells using clinostat rotation (clinorotation). Cell cultures were rotated for 72 h at 40 rpm in a clinostat. At the end of clinorotation, the cells were treated with TNF-alpha for 30 min under stationary conditions. Electrophoretic mobility shift assays revealed that TNF-alpha-dependent activation of NF-kappa B was markedly reduced in the clinorotated cells when compared with the cells in control stationary cultures or after horizontal rotation (motional controls). The NF-kappa B-dependent transactivation was also impaired in the clinorotated cells, as evidenced by a transient transfection assay with a reporter plasmid containing multimerized NF-kappa B sites. Consistent with these findings, the TNF-alpha-dependent induction of endogenous NF-kappa B-responsive genes p105, I kappa B-alpha, and IL-8, was significantly attenuate in clinorotated cells. These results demonstrate that vector-averaged gravity inhibits the responsiveness of osteoblasts to TNF-alpha by repressing NF-kappa B activation.

Base Sequence↗
PubMed1996

Capillarity Effects on Viscous Gravity Spreadings of Wetting Liquids.

Highly viscous silicone oils within a wide range of volumes were left to spread on smooth horizontal substrates to investigate the effects of capillarity on viscous gravity spreadings under the condition of complete wetting. The study was centered on the intermediate asymptotic behavior, where the details of the initial liquid distribution are irrelevant. We detected small but appreciable departures from the well-known solution without surface tension forces (viscous gravity self similar solution, or base solution). Two stages are clearly identified in the spreadings. During the first, which is usually rather brief, capillarity does not play an appreciable role on the dynamics of the spreading, i.e., the base solution is a very good approximation. The head of the current displays a wheel-like profile progressively decreasing in size; when the size becomes on the order of the capillary length, this stage ends. The wheel-like configuration cannot be associated either with the rheological behavior of the fluid used or with the initial conditions. To observe this first stage without the influences due to peculiarities of the initial conditions, a proper release of the spreading is needed. The second stage is characterized by a spreading rate below the base solution; the slowing is associated with a change of the current head shape, which takes the form of a wedge as a consequence of capillarity. The rate of advance of the front may still be well approximated by the same power law as given by the base solution, but with a smaller prefactor. In this work we measure the parameters that characterize the flow during both stages; besides, for the second stage, we develop a heuristic calculation which shows that the wedge-like shape of the current head gives place to a higher viscous dissipation rate, thus explaining the observed slowing of the spreading.

Journal Article↗
PubMed2000

Aggregation of Charged Particles under Electrophoresis or Gravity at Arbitrary Péclet Numbers.

Collision efficiencies are considered for colloidal suspensions of solid spheres moving in a viscous fluid under the influence of electrophoresis or gravity, Brownian motion, and electrostatic and van der Waals forces. The results are compared to those for convection (electrophoresis or gravity) and diffusion (Brownian motion) acting independently. The collision efficiency increases by many orders of magnitude over that predicted by simply adding diffusive and convective efficiencies in a specific parameter regime. This regime occurs when there is a large energy barrier in the interparticle potential, causing a stable region of parameter space if there is no diffusion. Brownian motion alone will only cause small amounts of aggregation under these conditions. However, for electric fields or buoyancy effects which are only slightly too weak to allow particles to overcome the potential barrier, the addition of weak Brownian motion to a system with convection can cause significant numbers of particles to overcome the energy barrier and aggregate. Copyright 2000 Academic Press.

Journal Article↗
PubMed1985

Electron-microscopic observations of the gravity receptor epithelia of normal and spinner juvenile Octopus maya.

Light and electron microscopy of the gravity receptor epithelia (maculae) of statocysts of normal and "spinner" juvenile Octopus maya showed differences between the structures of the hair cells, supporting cells, and afferent neurons of these cephalopods. The maculae of spinner animals were approximately 30% smaller in their surface area and had 40% fewer hair cells. Moreover, the average distance between randomly-chosen hair bundles in scanning electron micrographs of maculae of normal animals was significantly greater (4.33 +/- 6.47 microns) than those of maculae of spinner animals (3.38 +/- 4.90 microns; P less than 0.0001). The sectional area of the supporting cell's microvilli in spinner maculae was larger (0.16 +/- 0.18 microns) than those of normal (0.10 +/- 0.10 micron; P less than 0.0001) O. maya. The morphological differences observed between certain structural components of the maculae of normal and spinner O. maya may be related to the absence and/or malformation of the neuroepithelial suprastructures in spinners. This may have direct or indirect effects to their inability to orient to gravity with these organs.

Acoustic Maculae↗
PubMed1986

Mass-discrimination in weightlessness and readaptation to earth's gravity.

Five members of the first Spacelab mission (STS-9) were tested on several occasions for weight-discrimination before and after the flight, and for mass-discrimination under microgravity in flight. Thresholds for mass-discrimination were higher than for preflight weight-discrimination by a factor of about 1.8, and there was no clear evidence of improvement throughout the ten day mission. Too few tests were conducted to monitor the improvement during the first two days of flight, when adaptation to weightlessness may have occurred. Subjects reported perceptual aftereffects of body heaviness for two or three days after the flight. Their weight-discrimination thresholds were raised during this period, when they were re-adapting to normal gravity. Incomplete adaptation to altered arm weight can only partly explain the raised threshold for mass-discrimination in microgravity. Differences in the sensory information available with and without gravity are discussed.

Adaptation, Physiological↗
PubMed1994

Hydrocephalus: the zero ICP ventricle shunt (ZIPS) to control gravity shunt flow. A clinical study in 56 patients.

Significant morbidity from ventricle shunt overdrainage at 6-7 years after initial shunt placement for hydrocephalus is increasingly recognized as due to excessive gravity-flow of shunted CSF when upright. Shunts are designed primarily to control high ICP. Shunts should also mimic normal upright ICP. Normal upright ICP is -65 mm of water (vertex reference), indicating that a level of zero ICP exists at 65 mm below the brain vertex, with negative ICP above and positive ICP below that level. This normal zero ICP level must be maintained by CSF shunts to mimic normal upright ICP. This will prevent and correct CSF shunt overdrainage. The zero ICP shunt (ZIPS) by design controls this zero level with a zero pressure device (ZPD; siphon control device) installed at the normal vertical level of zero ICP (cm/mm) below the vertex (65 mm). The shunt thus prevents excessive gravity-induced CSF shunt flow. Successful use of ZIPS in 56 patients is reported (low ICP group: n = 42; high ICP group: n = 14). Follow-up is up to 4.5 years. Results show that: (1) adjustability of ZPD level can achieve the desired clinical results; (2) the level of ZPD installed correlates within 4 mm of upright ICP attained; (3) the optimal level of ZPD installation to produce normal upright ICP is 65 mm below the vertex; (4) CT ventricle size, both slit ventricles and large ventricles, may or may not normalize when normal upright ICP is attained in this group of complex, previously shunted patients.

Cerebral Ventricles↗
PubMed1980

Mutants of Arabidopsis thaliana with altered responses to auxins and gravity.

Auxin-resistant mutants of Arabidopsis have been induced and isolated by screening for survivors on a medium containing the herbicide 2,4-D. Thirty independently arisen mutants have been isolated in this way and one of them, P 83, has been investigated in detail. When wild type and P 83 are compared in concentration/response curves, where the response is the inhibition of root growth, the ED50 values of the auxins, 2,4-D and IAA, are 14-fold higher for the mutant. The mutant also responds differently to gravity: its roots do not show positive geotropism, but tend to grow with a clockwise curvature on agar surfaces. The seedling roots of the mutant also grow more rapidly than those of the wild type in the absence of 2,4-D, following faster germination. The F1 between P 83 and wild type is similar to the latter, but has a slightly increased resistance to 2,4-D. Results obtained from the F2, F3 and backcross generations suggest monofactorial inheritance. Most of the other 29 mutants have the P 83 phenotype, but at least five are different. Four have lower levels of resistance to 2,4-D and P 83, and their roots appear to respond normally to gravity. One mutant has an abnormal georesponse and a much higher level of resistance to 2,4-D than P 83.

Dose-Response Relationship, Drug↗
PubMedDate not supplied

Does head-down tilt simulate zero gravity?

Six anesthetized female rhesus monkeys were studied to determine the effect of head-down tilt on renal function. Head-down tilt is believed to simulate zero gravity. Some animals were tilted from 0 degree to -5 degrees or -10 degrees and others from +10 degrees to -10 degrees. None of these maneuvers consistently altered renal function. These results are in accord with those reported in early literature for the human but contrary to more recent reports. The interpretation of the latter are seriously hampered by experimental design. If indeed zero gravity translocates blood to the thorax with a resultant diuresis and natriuresis, head-down tilt is not an appropriate model for weightlessness.

Animals↗