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Research in plant physiology consists mostly of studies on plant growth because almost everything a plant does is done by growing. Most aspects of plant growth are strongly influenced by the earth's gravity vector. Research on those phenomena address scientific questions specifically about how plants use gravity to guide their growth processes.
Graviperception by plant roots is believed to occur via the sedimentation of amyloplasts in columella cells of the root cap. This physical stimulus results in an accumulation of calcium on the lower side of the cap, which in turn induces gravicurvature. In this paper we present a model for root gravitropism integrating gravity-induced changes in electrical potential, cytochemical localization of calcium in cells of gravistimulated roots, and the interdependence of calcium and auxin movement. Key features of the model are that 1) gravity-induced redistribution of calcium is an early event in the transduction mechanism, and 2) apoplastic movement of calcium through the root-cap mucilage may be an important component of the pathway for calcium movement.
The passage and specific gravity of nylon capsules were evaluated in five trials. In individual trials, different lactating cows were fed the same diet consisting of maize silage, alfalfa hay and concentrate. In each trial the different feeds (or no feed) were used to fill the capsules. The capsules were made of nylon cloth (42 microm pore size, 10 mm external diameter). The different weights of the load (L1-L5) were obtained using a combination of 2 and 3 mm stainless steel balls. The highest recovery of the capsules was obtained with the L3 and L4 loads (91.4 and 92.3%, resp.). After 14 hours of incubation in the rumen, the calculated values of functional specific gravity of the capsules ranged from 0.92 to 2.05 g x cm(-3). It was concluded that L3 (one 2 mm and one 3 mm ball) was the suitable weight of the load.
An artificial gravity and ergometric exercise loading device for human use was manufactured. It has the capacity of a max 2 G-load at the heart level, and a max 150 W of work-load. Eight subjects (six completed) were subjected to four repeated trials with or without 20 W ergometric exercise. Anti-G score, defined as the G-load x running time to the endpoint, was significantly higher in the exercise trials than standing trials. Heart rate (HR), mean arterial pressure (MAP), thoracic fluid index (TFI) were significantly superior during the exercise trials. Artificial gravity by centrifuge at 1.2 or 1.4 G with 40 or 60 W of ergometric workload may be an excellent countermeasure against cardiovascular deconditioning after long exposure to microgravity.
In this study, we extended our previous observations on the effects of altered gravity on the "lipoxygenase pathway", by ascertain the possible role of the force of gravity in modulating the activity and expression of PHS in human erythro-leukemia K562 cells.
For the first time, in altered gravity, with antifibrillarin antibodies and immunogold microscopy fibrillarin that is one of the most important proteins of rRNA processing was localized. The quantitative study of the density of gold particles in the nuclelous, under clinorotation both the transition zone FC-DFC and the dense fibrillar component were less labeled as compared to the control. Obtained data allow us to suppose the lowering of the rRNA processing level in the nucleoli under the influence of altered gravity.
We reported that elongation growth of plant shoots and roots is suppressed by hypergravity, with the rate decreasing in proportion to logarithm of the magnitude of gravity. In hypergravity-induced growth inhibition of shoots, graviperception is supposed to be independent of that in gravitropism and to involve mechanoreceptors. However, the graviperception mechanism in the hypergravity-induced growth inhibition of roots is not known. In the present study, we compared the mechanism in the hypergravity-induced growth inhibition of roots with that in gravitropism. The removal of root cap did not influence hypergravity-induced growth inhibition of roots, although the gravitropic curvature was completely inhibited. Hypergravity had no effects on growth of azuki bean roots in the presence of lanthanum or gadolinium, which are blockers of mechanoreceptors. On the contrary, lanthanum or gadolinium at the same concentration did not influence gravitropism of roots. These results suggest that the graviperception mechanism in the hypergravity-induced growth inhibition of roots is independent of that in gravitropism. Hypergravity-induced growth inhibition of azuki bean roots was observed irrespective of the direction of stimuli, which disappeared in the presence of lanthanum or gadolinium. Thus, in the hypergravity-induced growth inhibition, roots may perceive the gravity signal by mechanoreceptors on the plasma membrane independently of the direction of stimuli, and may utilize it to regulate their growth rate.
The correlation between osmolality and specific gravity of parenteral nutrition solutions containing various concentrations of amino acid and glucose were studied. There is good correlation between osmolality and specific gravity up to 1,000 mOsmol/kg H2O and 1.050, respectively. There are strong correlations between osmolality and amino acid concentration at each concentration of glucose. An equation which can be applied for quick calculation of osmolality of the solution from amino acid and glucose concentrations is: Osmolality (mOsmol/kg H2O) = 74.36 G + 163.91 A - 36.56. The results of this study can be adopted by all physicians for quick assessment of the osmolality of the PNS before administration to patients.
A series of pioneering experiments on adaptation to rotating artificial gravity environments was conducted in the 1960s. The results of these experiments led to the general belief that humans with normal vestibular function would not be able to adapt to rotating environments with angular velocities above 3 or 4 rpm. By contrast, our recent work has shown that sensory-motor adaptation to 10 rpm can be achieved relatively easily and quickly if subjects make the same movement repeatedly. This repetition allows the nervous system to gauge how the Coriolis forces generated by movements in a rotating reference frame are deflecting movement paths and endpoints and to institute corrective adaptations. Independent mechanisms appear to underlie restoration of straight movement paths and of accurate movement endpoints. Control of head movements involves adaptation of vestibulo-collic and vestibulo-spinal mechanisms as well as adaptation to motor control of the head as an inertial mass. The vestibular adaptation has a long time constant and the motor adaptation a short one. Surprisingly, Coriolis forces generated by natural turning and reaching movements in our normal environment are typically larger than those elicited in rotating artificial gravity environments. They are not recognized as such because self-generated Coriolis forces during voluntary trunk rotation are perceptually transparent. After adaptation to a rotating environment is complete, the Coriolis forces generated by movements within it also become transparent and are not felt although they are still present.
Postrace urine samples from thoroughbred horses were examined to compare osmolality and specific gravity between horses treated with furosemide and those not treated. Samples were assigned to groups in relation to reported medication (furosemide) status, race finish position, and distance of race. Urine osmolality was significantly (P <.05) lower in samples from horses treated with furosemide when compared with untreated horses. Specific gravity determinations are less precise at measuring urine osmolality at lower levels (1.01 g/ml or less). The measurement of osmolality is a superior method for determining the urine solute concentration and facilitating the regulation of furosemide.
The comparison of specific gravity values of 561 urine samples from TS meter and reagent strip was made. The data were divided into two groups: group 1-less than 2+ protein contained urine samples and group 2--equal or more than 2+ protein contained urine samples. The results revealed that the specific gravity values from both methods in both groups were statistically different (p less than 0.01) but they were correlated at r = 0.84 (p less than 0.001) and r = 0.73 (p less than 0.001) in group 1 and group 2, respectively. It was concluded that the reagent strip is suitable for use as a screening test but it should not be considered when precise measurement is necessary.
Vesicoureteral reflux was defined as unilateral in 17 of 36 cases. Urine was collected from both kidneys. Urine specific gravity and osmolality were significantly reduced; beta 2-microglobulin was elevated and lactoferrin depressed on the reflux side. We also observed a significant correlation between specific gravity or osmolality on one side and lactoferrin on the other side, and between osmolality and beta 2-microglobulin. These observations showed a depressed concentrating capacity and reduced tubular absorption of beta 2-microglobulin suggesting reduced tubular function on the reflux side.
Corrections for specific gravity, osmolality, and creatinine were applied to identical urinary mercury data in order to investigate the reproducibility of the corrected mercury concentration in a person's urinary spot samples throughout a 24-hour period; and the extent to which it is possible to predict a person's 24-hour mercury excretion from the corrected mercury concentration in the corresponding spot samples. The data indicate that on the average these corrections improve reproducibility by a factor of approximately 2. In individual cases, the uncorrected and corrected values of mercury concentration can differ by as much as a factor of 6. Similar effects were observed in the correlation of the mercury concentration of a spot sample and the corresponding 24-hour excretion of mercury. For this set of data, the corrections for specific gravity and osmolality turned out to be almost identical. The correction for creatinine was more effective than the other corrections by a small but statistically significant amount.
Human T cells from peripheral blood, cord blood, thymus, spleen and lymph node were analysed for their proliferative response capacity to mitogens, for their specific gravity and size, and for their binding capacity of peanut agglutinin. A close correlation was found between these parameters: thymocytes and T cells from spleen were consistently heavier and smaller, and showed a lower proliferative response capacity, than T cells from blood or lymph node. Similarly, within each cell population, the small, heavy cells were least reactive. The limiting-dilution analysis revealed that heavy T cells from peripheral blood contain a lower number of reactive cells than the light peripheral T lymphocytes. Because heavy T cells from the thymus bound more peanut lectin than did light cells, it is speculated that the differences between T cells of high and low specific gravity might reflect differences in maturation level.
The difference between the specific gravity of blood and contrast medium and the consequent tendency of contrast media to fill the lower tissues is exploited in abdominal angiography by special positioning of patients: prone for the coeliac, hepatic and mesenteric arteries, prone with the legs raised for abdominal aortography; lateral decubitus on the side of interest for renal angiography. The advantages are better parenchymal opacification, increased contrast and improved details. Gravity positioning saves time and material, and is easy to learn.
An air force anti-gravity suit, as used by fighter pilots to prevent loss of consciousness, has been successfully employed to treat severe postural hypotension in a patient with Shy-Drager syndrome. The definition of postural hypotension is reviewed, and reference is made to the previous use of the anti-gravity suit in the treatment of this condition.
The proprioceptive position sense was investigated in an elbow-angle matching task in which the right forearm was moved passively by an experimenter and the left forearm actively by the subject. The right forearm could be immersed in water or loaded with a weight, to simulate micro- and hypergravity. We found that in simulated microgravity, matching performance was more variable than in normal gravity, and the right forearm deviated systematically upwards. The latter finding was limited to near-horizontal forearm positions (i.e., where the anticipated effects of gravity are strongest), and could be "reset" by intermittent visual feedback. The observed impairments of the proprioceptive position sense may adversely affect the manual performance of astronauts. In simulated hypergravity, we found no changes of variability and no systematic deviations. This outcome confirms our previous results that weight compensation is efficient even when only static (i.e., gravitational) cues are available.
The specific gravity and weight of eggs were determined for two groups of 600 eggs each, originating from Nicholas and British United Turkey of America (BUTA) turkey breeder flocks. A total of 137 Nicholas and 190 BUTA toms hatched from these eggs were used for the experiment. At days 21, 33, 40, 47, 56, and 61, toms that showed retarded growth were euthanatized, along with a corresponding number of normal birds. Both groups were measured for body weight, heart weight, separate weights of left and right ventricles, and combined atrial weight. At market age, the remaining toms were weighed, and the hearts were checked at processing for lesions characteristic of spontaneous turkey cardiomyopathy (STC). STC was found in 10.2% of Nicholas and 8.4% of BUTA toms. No correlation could be found between specific gravity of eggs and incidence of STC. Body weights of affected toms were reduced during the growing period. At processing, 2.8% of toms had lesions of STC, and mean body weight was 1298 g lower than average. The ratios of combined atrial weight:body weight, right ventricular weight:body weight, left ventricular weight:body weight, and total heart:body weight were significantly higher at all times in affected toms than in controls, and the differences were the greatest at 3 weeks of age.