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The specific gravity of 71 CSF samples from clinically normal dogs ranged from 1.004 to 1.006, with a mean of 1.005. A 3-year retrospective study of CSF samples obtained from 124 animals suspected of having neurologic disease revealed only 30 samples (24.2%) having a specific gravity greater than 1.006. Diagnostic or prognostic value from CSF specific gravity determination was not recognized.
A newly developed reagent strip method for determination of urinary specific gravity is described. This reagent strip (Chemical S.G., Ames Co.) contains polyelectrolyte which is sensitive to the cation in solution. The urinary specific gravity is mainly decided by cation (Na+ and K+) concentrations in urine. As a result, the reagent strip gave measurements that corresponded to those measured by refractometry and gravimetry of NaC1 solution. Urea and glucose gave increased values by the refractometer, whereas the reagent strip did not cause changes. The values of urinary specific gravity obtained from reagent strip showed not only good correlations (r = 0.79-0.93) with the refractometry and gravimetry but also urinary osmolarity. This reagent strip method proved to be a most convenient tool for routine urinalysis because of the good reproducibility and accuracy considering its easy handling.
A method is proposed for urine specific gravity determination by urine refractometric index reading. Only two-three drops are required. Abbe refractometer is used. The urine specific gravity is determined by the formula: (formula: see text), where y = urine specific gravity, x = the refraction read. The method could not be used in cases with glucosuria and ketoniria as well as in case of a considerable proteinemia. The author's results correlate with the results of some foreign authors.
Inversion in a head-down position (gravity inversion) results in an intraocular pressure of 35 to 40 mm Hg in normal subjects. We used computerized static perimetry to measure the visual fields of normal subjects during gravity inversion. There were no visual field changes in the central 6 degrees of the visual field compared with the baseline (preinversion) values. However, when the central 30 degrees of the visual field was tested, reversible visual field defects were found in 11 of 19 eyes. We believe that the substantial elevation of intraocular pressure during gravity inversion may pose potential risks to the eyes, and we recommend that inversion for extended periods of time be avoided.
Segmental parameters (mass, center-of-gravity, and moment-of-inertia) are necessary for biomechanical analyses of a species' locomotor behavior. Seven male and eight female adult rhesus monkey cadavers were dismembered in order to determine segmental parameters. Mean values for the segment masses and moments-of-inertia are presented for males and females, separately and together. Statistical tests revealed significant differences between the sexes for these parameters. Regression equations for predicting segment masses and moments-on-inertia were developed for the sexes separately and pooled. For most segments the male and female equations did not differ significantly in slope or y-intercept. The center-of-gravity for each segment is presented as a mean percentage of the distance between the proximal and distal joint centers. The regression equations and center-of-gravity locations presented here permit biomechanical investigations of rhesus monkey locomotion without the necessity of subsequent sacrifice. The segmental parameter values determined for the rhesus monkey are compared with available data for other primate and mammalian species and the biomechanical and adaptive implications of such comparisons are discussed.
A novel, h-shaped ultrasonic resonator was used to separate biological particulates. The effectiveness of the resonator was demonstrated using suspensions of the cyanobacterium, Spirulina platensis. The key advantages of this approach were improved acoustic field homogeneity, flow characteristics, and overall separation efficiency (sigma = 1 - ratio of concentration in cleared phase to input), monitored using a turbidity sensor. The novel separation concept was also effective under microgravity conditions; gravitational forces influenced overall efficiency. Separation of Spirulina at cleared flow rates of 14 to 58 L/day, as assessed by remote video recording, was evaluated under both microgravity (</=0.05 g) and terrestrial gravity conditions. The latter involved a comparison with 5- and 24-microm-diameter polystyrene microspheres. Influences of gravity on sigma were evaluated by varying the relative inclination angle (within a range of 120 degrees ) between the resonator and the gravitational vector. Cells of Spirulina behaved in a manner comparable to that of the 5-microm-diameter polystyrene microspheres, with a significant decrease in mean (+/-SE, n = 3) sigma from 0.97 +/- 0.03 and 0.91 +/- 0.02 at a flow rate of 14 L/day, to corresponding values of 0.53 +/- 0.05 and 0.57 +/- 0.03 (P < 0.05) at 58 L/day, respectively. During a typical microgravity period of ca. 22 s, achieved during the 29th ESA Parabolic Flight Campaign, sigma was unchanged at a flow rate of 14 L/day, compared with terrestrial gravity conditions; with increased flow rates, sigma was significantly reduced. Overall, these results demonstrate that, for optimum resonator performance under the relatively short microgravity period utilized in this study, flow rates of ca. 14 L/day were preferred. These data provide a baseline for exploiting noninvasive, compact, ultrasonic separation systems for manipulating biological particulates under microgravity conditions.
To determine the influence of gravity on premature closure of prosthetic mitral valves, we studied 17 patients in whom this phenomenon had been observed during routine examination. All patients were in atrial fibrillation and none had aortic incompetence. Patients were studied in multiple positions by means of simultaneous echocardiography, phonocardiography, and cinefluoroscopy. In all patients premature closure was observed when the atrial side of the prosthesis was below the ventricular side, resulting in a downward motion of the occluder inside the valve cage. When patients were studied in positions in which the atrial side of the valve was higher that the ventricular side, premature closure never occurred, even during extremely prolonged diastolic periods. Since minor positional changes, which were found to determine whether premature closure occurred or not, are unlikely to produce significant alterations in pressure and flow across the mitral orifice during diastole, we conclude that position-dependent premature closure of prosthetic mitral valves in patients with atrial fibrillation is best explained by the effect of gravity on the prosthetic occluder. Examination of such patients in multiple positions should be helpful in distinguishing premature valve closure caused by aortic regurgitation from gravity-related presystolic closure. Inability to produce premature closure in patients in whom it had previously been demonstrated in the presence of similar R-R intervals may even prove useful in diagnosing new orifice obstruction.
Atomic force microscopy (AFM) was used to study the effect of gravitational forces on the deposition of submicrometer colloidal particles onto solid surfaces to test the usual assumption that the contribution of gravity to the behavior of particles with diameters <1 &mgr;m is negligible. The effects of both particle size and density were examined using polystyrene sulfate latex, silica, and colloidal gold particles of several sizes ranging from 10 nm to 1 &mgr;m. The results show that significant differences are observed in the deposition of colloidal particles onto horizontal and vertical surfaces, under identical suspension conditions and exposure times, showing that gravitational forces can have a considerable effect. This effect was quantified by analysis of the AFM images. The experimental results are compared to calculations of the expected coverage and particle surface concentration assuming diffusion-limited adsorption and deposition by sedimentation. Gravity can be negligible for low-density particles with diameters considerably smaller than 1 &mgr;m. However, if the density of the colloidal particles is high, as in the case of colloidal gold, gravity can become a significant driving force for particle transport to the surface, even for particles with diameters much smaller than 100 nm. Copyright 2001 Academic Press.
The idea that gravity affects dorso-ventral polarization in anouran development contrasts with the theories of self-organization through reaction-diffusion processes. As a result of a literature study we discuss the role of gravity in embryological axis formation and speculate on an influence of gravity on tissue compartmentalization. The involvement of compartmentalization in tissue homeostasis is discussed in the light of the recent progress in mammalian cell culture studies.
Honey bees have long been assumed to build their comb with the cells in either of two preferred orientations with respect to gravity ("vertical" or "horizontal"). I show here that these typical cell orientations in fact derive from substrate orientation and a simple building rule, rather than the influence of gravity itself. When bees were induced to build comb on substrates at four different orientations with respect to gravity, they always made cells with one vertex pointing directly toward the substrate. This produced horizontal and vertical cells on vertical and horizontal substrates, respectively, but yielded intermediate orientations on oblique substrates. The apparent preference for vertical and horizontal cells may simply reflect substrate orientation in the rectilinear hives from which cell measurements have been taken.
There is a high variance in sagittal morphology and complaints between different subjects suffering from spinal disorders. Sagittal spinal alignment and clinical presentation are not closely related. Different parameters have been used to describe the pelvispinal morphology based on standing lateral radiographs. We conducted a study using radiography of the lumbar spine combined with force platform data to examine the correlation between pelvispinal parameters and the gravity line position. Fifty consecutive patients with a mean age of 55 years (18-84 years) were compared to normal controls. Among patients we found a statistically significant correlation between the following spinal parameters: lumbar lordosis and sacral slope (r=0.77; P<0.001), sacral slope and pelvic incidence (r=0.72; P<0.001) and pelvic tilt and overhang (r=-0.93; P<0.001). In patients and controls, the gravity line position was found to be located at 60 and 61%, respectively, of the foot length measured from the great toe, ranging from 53 to 69%, when corrected for the individual foot length. The results indicate that subjects with and without spinal disorders have their gravity line position localised within a very small range despite the high variability for lumbar lordosis and pelvic tilt.
Similar to the response to central hypervolemic conditions on Earth, the shift of blood volume from the legs to the upper part of the body in astronauts entering micro-gravity should, in accordance with the Henry-Gauer mechanism, mediate diuresis and natriuresis. However, fluid balance and kidney function experiments during various space missions resulted in the surprising observation that the responses qualitatively differ from those observed during simulations of hypervolemia on Earth. There is some evidence that the attenuated responses of the kidney while entering weightlessness, and also later during space flight, may be caused by augmented fluid distribution to extravascular compartments compared to conditions on Earth. A functional decoupling of the kidney may also contribute to the observation that renal responses during exposure to micro-gravity are consistently weaker than those during simulation experiments before space flight. Deficits in body mass after landing have always been interpreted as an indication of absolute fluid loss early during space missions. However, recent data suggest that body mass changes during space flight are rather the consequences of hypocaloric nutrition and can be overcome by improved nutrition schemes. Finally, sodium-retaining humoral systems are activated during space flight and may contribute to a new steady-state of metabolic balances with a pronounced increase in body sodium compared to respective conditions on Earth. A revision of the classical "micro-gravity fluid shift" scheme is required.
Seedlings of most cucurbitaceous plants develop a peg (protuberance caused by cell outgrowth) on the transition zone between the hypocotyl and root. The peg is necessary for removing the seed coat after germination. In our spaceflight experiments on the STS-95 space shuttle, Discovery, we found that cucumber (Cucumis sativus L.) seedlings grown under microgravity conditions developed two pegs symmetrically at the transition zone. Thus, cucumber seedlings potentially develop two pegs and do not require gravity for peg formation itself, but on the ground the development of one peg is suppressed in response to gravity. This may be considered as negative control of morphogenesis by gravity.
Holding the body's centre of gravity steady represents the crucial variable for the stabilization of posture in upright stance in man. The visual, vestibular and muscle proprioceptive systems have all been shown to contribute to sway stabilization. Nevertheless, earlier work has suggested that an additional receptor system is needed to signal the position of the body's centre of gravity relative to the support surface, i.e., the feet. This proposed receptor system should be 'gravity' dependent. To evaluate the properties of this receptor system, an experiment was designed under simulated 'microgravity', in water immersion. An approximately linear relationship was found between contact force and impulse directed EMG response amplitudes in the leg muscles. Out of water loading of the subjects resulted in no further increase of the response amplitude. A gain control mechanism for postural reflexes which is dependent on body weight was demonstrated. In a further experiment it could be shown that the receptors for this mechanism are distributed along the vertical axis of the body: it is suggested that these force-dependent receptors are pressure receptors within the joints and the vertebral column.
A number of studies have suggested that gravity changes may influence mammalian cell growth and differentiation. To obtain insight in the molecular mechanisms underlying these effects, we have studied immediate early gene expression in response to activation of cytoplasmic signal transduction under microgravity conditions. In this paper we show that epidermal growth factor (EGF)- and 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-induced expression of the c-fos and c-jun protooncogenes is decreased in microgravity, while no effect of gravity changes was observed on A23187- and forskolin-induced expression of these genes. These decrease in c-fos expression was not due to delayed kinetics under microgravity. These results demonstrate that gravity differentially modulates distinctive signal transduction pathways.
A general, dynamic relationship between the data obtained from a force platform, center of gravity of the body on the platform and the time rate of change of moment of momentum of the body about its center of gravity was derived from principles of dynamics for a system of particles. The derived equations are useful for processing and interpreting the force platform data. Displacement and path of center of gravity of human body during standing on one foot and level walking were estimated by using the derived equations. An estimation of the time rate of change of moment of momentum of the body was also obtained. A biomechanical interpretation of point of application of the resultant of ground reactions was presented.
Two-step crystallization experiments were conducted in low gravity employing a liquid-liquid diffusion method in an effort to eliminate problems associated with protein crystal growth under the supersaturating conditions required for nucleation. Experiments were performed in diffusion cells formed by the sliding of blocks on orbit. Step gradient diffusion experiments consisted of first exposing protein solutions in diffusion half-wells for brief periods to initiating buffer solutions of high precipitant concentrations to induce nucleation followed by expoure of the same protein solutions to solutions of lower precepitant concentration to promote growth of induced nuclei into crystals. To avoid convective disturbances that occur when solutions of discrepant densities are interfaced at normal gravity, crystallization of hen egg-white lysozyme and rabbit skeletal muscle aldolase by step gradient diffusion was investigated in low gravity on four NASA space shuttle flights. In general, the largest ctystals of both proteins formed at the highest initiating precipitant concentration used, which is consistent with nuclei formation upon brief exposure to high precipitant concentration, and that these nuclei are competent for sustained growth at lower precipitant concentration. The two-step approach dissociates nucleation events from crystal growth allowing parameters affecting nucleation kinetics such as time, precipitant concentration and temperature of nucleation to be varied separately from conditions used for post-nucleation growth.
Inhalation risks on long-duration manned spaced flight include gasses chronically released by outgassing of materials, gasses released during spills, thermodegradation events (including fires) with their attendant particulates, and fire extinguishment. As an example, an event in which electronic insulation consisting of polytetrafluoroethylene undergoes thermodegradation on the Space Station Freedom was modeled experimentally and theoretically from the initial chemistry and convective transport through pulmonary deposition in humans. The low-gravity environment was found to impact various stages of event simulation. Critical unknowns were identified, and these include the extent of production of ultrafine particles and polymeric products at the source in low gravity, the transport of ultrafine particles in the spacecraft air quality control system, and the biological response of the lung, including alveolar macrophages, to this inhalation risk in low gravity.