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PubMed1997

Estimation of the composition of broiler carcasses from their specific gravity.

An experiment was conducted to quantify the relationships between broiler carcass specific gravity and chemical composition (percentage moisture, percentage lipid, percentage protein). Carcasses of widely varying compositions were produced by feeding several dietary protein and energy combinations (52 to 64% moisture, 0.6 to 2.5% ash, 1.6 to 11.7% lipid, and 4.9 to 8.0% nitrogen). Very strong relationships were found between percentage moisture and percentage lipid (r = -0.969) and percentage moisture and percentage N (r = 0.968). Strong relationships were found between specific gravity and percentage lipid (r = -0.872) and specific gravity and percentage N (r = 0.857). Specific gravity is recommended as a means to estimate carcass fat in broiler chickens.

Animals↗
PubMed1994

The response to gravity is correlated with the number of statoliths in Chara rhizoids.

In contrast to higher plants, Chara rhizoids have single membrane-bound compartments that appear to function as statoliths. Rhizoids were generated by germinating zygotes of Chara in either soil water (SW) medium or artificial pond water (APW) medium. Differential-interference-contrast microscopy demonstrated that rhizoids form SW-grown plants typically contain 50 to 60 statoliths per cell, whereas rhizoids from APW-grown plants contain 5 to 10 statoliths per cell. Rhizoids from SW are more responsive to gravity than rhizoids from APW because (a) SW rhizoids were oriented to gravity during vertical growth, whereas APW rhizoids were relatively disoriented, and (b) curvature of SW rhizoids was 3 to 4 times greater throughout the time course of curvature. The growth rate of APW rhizoids was significantly greater than that of SW-grown rhizoids. This latter result suggests that APW rhizoids are not limited in their ability for gravitropic curvature by growth and that these rhizoids are impaired in the early stages of gravitropism (i.e. gravity perception). Plants grown in APW appeared to be healthy because of their growth rate and the vigorous cytoplasmic streaming observed in the rhizoids. This study is comparable to earlier studies of gravitropism in starch-deficient mutants of higher plants and provides support for the role of statoliths in gravity perception.

Chlorophyta↗
PubMed2001

Changes in root cap pH are required for the gravity response of the Arabidopsis root.

Although the columella cells of the root cap have been identified as the site of gravity perception, the cellular events that mediate gravity signaling remain poorly understood. To determine if cytoplasmic and/or wall pH mediates the initial stages of root gravitropism, we combined a novel cell wall pH sensor (a cellulose binding domain peptide-Oregon green conjugate) and a cytoplasmic pH sensor (plants expressing pH-sensitive green fluorescent protein) to monitor pH dynamics throughout the graviresponding Arabidopsis root. The root cap apoplast acidified from pH 5.5 to 4.5 within 2 min of gravistimulation. Concomitantly, cytoplasmic pH increased in columella cells from 7.2 to 7.6 but was unchanged elsewhere in the root. These changes in cap pH preceded detectable tropic growth or growth-related pH changes in the elongation zone cell wall by 10 min. Altering the gravity-related columella cytoplasmic pH shift with caged protons delayed the gravitropic response. Together, these results suggest that alterations in root cap pH likely are involved in the initial events that mediate root gravity perception or signal transduction.

Arabidopsis↗
PubMed2006

Numerical simulation of local blood flow in the carotid and cerebral arteries under altered gravity.

A computational fluid dynamics (CFD) approach was presented to model the blood flows in the carotid bifurcation and the brain arteries under altered gravity. Physical models required for CFD simulation were introduced including a model for arterial wall motion due to fluid-wall interactions, a shear thinning fluid model of blood, a vascular bed model for outflow boundary conditions, and a model for autoregulation mechanism. The three-dimensional unsteady incompressible Navier-Stokes equations coupled with these models were solved iteratively using the pseudocompressibility method and dual time stepping. Gravity source terms were added to the Navier-Stokes equations to take the effect of gravity into account. For the treatment of complex geometry, a chimera overset grid technique was adopted to obtain connectivity between arterial branches. For code validation, computed results were compared with experimental data for both steady-state and time-dependent flows. This computational approach was then applied to blood flows through a realistic carotid bifurcation and two Circle of Willis models, one using an idealized geometry and the other using an anatomical data set. A three-dimensional Circle of Willis configuration was reconstructed from subject-specific magnetic resonance images using an image segmentation method. Through the numerical simulation of blood flow in two model problems, namely, the carotid bifurcation and the brain arteries, it was observed that the altered gravity has considerable effects on arterial contraction/dilatation and consequent changes in flow conditions.

Acceleration↗
PubMed2005

Effects of gravity and blood volume shifts on cardiogenic oscillations in respired gas.

During the cardiac cycle, cardiogenic oscillations of expired gas (x) concentrations (COS([x])) are generated. At the same time, there are heart-synchronous cardiogenic oscillations of airway flow (COS(flow)), where inflow occurs during systole. We hypothesized that both phenomena, although primarily generated by the heartbeat, would react differently to the cephalad blood shift caused by inflation of an anti-gravity (anti-G) suit and to changes in gravity. Twelve seated subjects performed a rebreathing-breath-holding-expiration maneuver with a gas mixture containing O2 and He at normal (1 G) and moderately increased gravity (2 G); an anti-G suit was inflated to 85 mmHg in each condition. When the anti-G suit was inflated, COS(flow) amplitude increased (P = 0.0028) at 1 G to 186% of the control value without inflation (1-G control) and at 2 G to 203% of the control value without inflation (2-G control). In contrast, the amplitude of COS of the concentration of the blood-soluble gas O2 (COS([O2/He])), an index of the differences in pulmonary perfusion between lung units, declined to 75% of the 1-G control value and to 74% of the 2-G control value (P = 0.0030). There were no significant changes in COS(flow) or COS([O2/He]) amplitudes with gravity. We conclude that the heart-synchronous mechanical agitation of the lungs, as expressed by COS(flow), is highly dependent on peripheral-to-central blood shifts. In contrast, COS([blood-soluble gas]) appears relatively independent of this mechanical agitation and seems to be determined mainly by differences in intrapulmonary perfusion.

Adaptation, Physiological↗
PubMed2002

Values of urine specific gravity for thoroughbred horses treated with furosemide prior to racing compared with untreated horses.

The distribution of specific gravity values for 2,599 urine samples collected from racing Thoroughbred horses that were known to have received furosemide prior to racing was compared with that for 1,669 urine samples from racing Thoroughbred horses that reportedly had not received furosemide. Values of specific gravity for furosemide-treated horses were significantly lower (P < 0.001) than those for horses that had not received furosemide, and the proportion of horses with urine specific gravity either <1.010 or <1.012 was significantly greater (P < 0.001) among the furosemide-treated horses. These data indicate that evaluation of urine specific gravity would be a useful component of drug testing programs for regulation of furosemide use.

Animals↗
PubMed1979

Falsely high refractometric readings for the specific gravity of pleural fluid.

For 128 pleural fluids, the relationship between the protein content and the reading for the specific gravity obtained from a refractometer calibrated for urinary specific gravity was analyzed. The refractometer gave falsely high levels for the specific gravity of the pleural fluid. A reading for 1.019 (rather than 1.016) corresponded to a concentration of protein of 3.0 gm/100 ml, and each deviation of 0.005 (rather than 0.003) coresponded to a concentration of 1 gm/100 ml; however, determinations of the concentration of protein in the pleural fluid directly from the refractometer's scale for protein (calibrated for serum) was rapid and accurate. Calculation of the protein content of the pleural fluid from the reading for specific gravity on the refractometer is erroneous and sometimes misleading.

False Positive Reactions↗
PubMed1981

[Relationship between the refractive index and specific gravity of the rat urine (author's transl)].

The relationship between the refractive index and specific gravity of urine was studied with specimens from 165 Sprague-Dawley rats, by graphic analysis of the plot of the refractometrically determined index against the specific gravity which was measured with a pycnometer. 1. A linear regression was demonstrated between the refractive index and specific gravity. 2. The nomogram fitted the data of even those samples with high refractive index and specific gravity, irrespective of changes in food or water intake and protein or glucose contents in the urine. 3. The nomogram was in good agreement, in respect of linearity, with the regression line derived from the conversion table of TS meter by the American Optical Corporation and also with the nomogram of the Japanese Society of Clinical Pathology. It approximated more closely to the former than to the latter.

Animals↗
PubMed1992

Kinetics of hydration and effect of liquid uptake on specific gravity of small hay and silage particles.

Kinetics of hydration of ground hay and silage particles (2-mm screen), determined by a pycnometric technique, was best described by a two- and one-pool exponential model, respectively. Fractional rates of hydration of the large pool, detected in hay particles only, and of the small pool present in both hay and silage particles averaged .135 and .021 min-1, respectively. When hydration was complete, liquid associated with particles averaged 1.16, 1.90, and .83 g/g of insoluble DM for bromegrass hay, alfalfa hay, and alfalfa silage, respectively. Functional specific gravity, which accounts for the effect of associated gas volume, averaged 1.54, 1.46, and 1.54, but unit specific gravity, calculated to include the effect of gases and liquid of hydration, averaged 1.22, 1.14, and 1.26 for bromegrass hay, alfalfa hay, and alfalfa silage, respectively. Preservation of forage as silage not only lowered gas volume, but also reduced water-holding capacity, both of which contribute to greater unit specific gravity and faster rate of escape from the rumen. In addition, estimates of unit specific gravity of approximately 1.2 indicate that even in the absence of associated gas, hydrated forage particles would tend to escape the rumen at a slower rate than that achieved by more dense particles.

Animal Feed↗
PubMed1991

Detection of gravity through nonequilibrium mechanisms.

Using the principles of physics, could we set a fundamental lower limit for the size of a cell that can respond to gravity? Pollard (1965) tried to obtain such a limit assuming a gravity sensing mechanism that could be described as a system in thermodynamic equilibrium. In this chapter, a dynamic gravity sensing mechanism that is not in thermodynamic equilibrium is considered. It is shown that under some conditions nonequilibrium systems can be more sensitive than equilibrium systems. The dynamic mechanism described here is able to respond to gravity by virtue of its ability to perform a process similar to "signal averaging" used in electronic detection of weak signals. Through this process, a system is able to respond to a small systematic force embedded in a larger but randomly fluctuating force.

Cell Movement↗
PubMed1991

Gravity sensing mechanisms in plant cells.

Sensing of gravity is essential for the survival of plant seedlings. Therefore it is understandable that gravistimulation of only 0.5 sec-duration causes a graviresponse. The earliest graviresponses could be measured within seconds as alterations in membrane potentials of the statocytes in the root cap. Root statocytes are polarly organized. From a 6-day microgravity (10(-3) - 10(-4) g) experiment in the Spacelab D1 Mission it has been concluded that the observed polar differentiation is a result of a genetically prepatterned developmental program. Statoliths, the sedimentable organelles of statocytes, are surrounded by actin filaments which partly keep them in position. Under 6 min of microgravity during parabolic flights of rockets it could be demonstrated that the statoliths moved in the opposite direction to the initial gravity vector. It is concluded that shearing forces are exerted by microfilaments. It is supposed that the change of the position of statoliths is transmitted to gravisensitive structures of the statocytes (ER, plasma membrane) via microfilaments. As graviperception is influenced by calcium ions, it is suggested that these interactions regulate the activity of ion channels and/or pumps in the membranes thus initiating the graviresponse chain. In the case of cytoplasmic streaming in Chara rhizoids, the endogenous difference between the opposing streaming directions is diminished under microgravity during the flights of rockets. Possibly, shear stresses are affected by gravity, thus inducing gravity-related differences in the streaming velocities via actin filaments.

Actin Cytoskeleton↗
PubMed1997

Body mass change during altered gravity: spaceflight, centrifugation, and return to 1 G.

To assess the effect of gravity on growth, immature rats (130-200 g) were studied during chronic altered gravity exposure and while transitioning between gravity fields. Body mass gain of rats (n = 12) exposed to 14 days of microgravity (spaceflight) was evaluated and compared to mass gain of 1 G controls. Spaceflight did not affect mass gain. Six rats exposed to 1 G following spaceflight, when compared to controls, experienced a significant (0 < 0.05) post-flight mass loss over 48 h of 13 g. Over subsequent days, however, this loss was compensated for, and no difference from 1 G controls was noted after 5 days. Exposure to hypergravity (2 G) for 16 days was evaluated [(n = 6/group): Centrifuge (C); On Center Control (OCC); Centrifuge Control (CC)]. Body mass of centrifuged and OCC rats was reduced within 24 h, with OCCs regaining control mass within 13 days. The mass difference (44 g) in centrifuged animals persisted, however, with no subsequent difference in rate of mass gain between centrifuged animals and controls over Days 3-16 (3.7 +/- 0.1 vs. 3.9 +/- 0.1 g/day, respectively). Transitioning from 2 G to 1 G resulted in a mass increase within 48 hours for centrifuged animals. Over Days 3-16 at 1 G, the rate of gain for centrifuged animals continued to increase (3.1 +/- 0.1 g/day compared to 2.1 +/- 0.1 g/day for controls); differences from control, however, were still noted on Day 16. Transitioning to an increase in a gravity field causes acute losses in body mass. In hypergravity, the acute reduction in body mass persists but the rate of mass gain is normal. Animals returning to 1 G, after acute changes, adjust to attain control mass.

Adaptation, Physiological↗
PubMed1973

Gravity sensing by plants.

A brief description of the effects of gravity on plants, particularly their orientation with reference to its direction, is followed by a presentation of evidence for the operation of specific "gravity sensors", statoliths, subcellular bodies which move or reorient themselves upon reorientation of a plant organ with respect to the direction of the force of gravity. In the singly reacting apical cells of rhizoids of Chara, the statoliths locally regulate the growth of the cell wall simply by blocking or permitting the access of carriers of cell wall material. In multicellular structures (root and stem tips etc.) the statoliths, most likely amyloplasts (starch-containing plastids), must act by creating in the organ a transversal polarity which can be transmitted to the growing region, often several millimetres away. In addition, gravity produces what may be called tonic effects, which quantitatively modify the reaction of the organ to the gravitational stimulation.

Chlorophyta↗
PubMed2004

Gravity-regulated proteins of Arabidopsis and cucumber seedlings detected by 2-D electrophoresis.

Gravity exerts a profound influence on plant growth. Proteomics may be the most promising technique to identify the proteins that are induced, repressed, or post-transcriptionally modified during gravity response in plants. In this research, the model plant, Arabidopsis grown in stationary and clino-rotated condition for 7 to 10 days and cucumber plant with the unique gravimorphogenesis were used. Namely, cucurbit seedlings develop a peg on the transition zone between the hypocotyls and root. Cucumber seedlings grown in a horizontal position on the ground suppress the development of the peg (negatively-controlled) on the upper side of the transition zone in response to gravity. Then, we analyzed gravity-regulated proteins expression by two-dimensional (2-D) gel electrophoresis.

Arabidopsis↗
PubMed1987

Specific gravity measurements of lamb carcass joints.

10 Ossimi lamb carcasses were used to determine the specific gravity values of different joint cuts. The correlation coefficients were established between the specific gravities of these joints and the percentages of fat and muscle in the rib saddle joint. It was found that the gravity of different carcass sections was significantly related to the muscle and fat percentages in the rib saddle joint. The results indicate that the specific gravity values of carcass sections can be utilized for a practical estimate and assessment of carcass components.

Adipose Tissue↗
PubMed1986

Relationships among serum immunoglobulin concentration in foals, colostral specific gravity, and colostral immunoglobulin concentration.

Postpartum, presuckle, colostrum samples were collected from 100 mares. Colostral specific gravities significantly correlated (r = 0.9) with colostral immunoglobulin (Ig)G concentrations. Foal serum IgG concentrations highly correlated (r = 0.82) with specific gravities of the colostrum each foal ingested. Eight of 48 foals (17%) had serum IgG concentrations less than 400 mg/dl. The dams of these 8 foals had colostral sp gr less than 1.06 and colostral IgG concentrations less than 3,000 mg/dl. Foals had serum IgG concentrations greater than 520 mg/dl 24 hours after parturition, when the colostral specific gravity of the dam was greater than or equal to 1.06. Effects of breed on colostral specific gravity, colostral IgG concentrations, foal serum IgG concentrations, and mare serum IgG concentrations were not significant.

Animals↗
PubMed1984

[Adjustment of urinary delta-aminolevulinic acid concentrations in workers exposed to lead and heat. Adjustments of specific gravity to 1.020 and urinary volume coefficients].

Adjustments of urinary ALA concentrations as to urinary specific gravity and creatinine were examined for workers exposed to lead and heat. Judging from our findings, we suggested that it was preferable to adopt the specific gravity (UG) at 1.020 as the adjustment value to obtain the correct urinary ALA concentration. Though corrected values thus obtained were found adequate for urine in the normal range of specific gravity, they failed to be adequate for concentrated urine samples higher than UG 1.025. Urinary volume adjustment was found to be necessary for these concentrated urine in stead of urinary specific gravity adjustment. For the practical purposes, we postulated urinary volume coefficients, which were estimated to be 0.5 for samples ranging from UG 1.026 to 1.030, 0.4 for samples from UG 1.031 to 1.035 and 0.3 for samples from UG 1.036 to 1.040, respectively.

Aminolevulinic Acid↗
PubMed1982

Effect of intravenous fluid and drug solution coadministration on final-infusate osmolality, specific gravity, and pH.

The effects of i.v. fluid rates and i.v. drug delivery rates on osmolality, specific gravity, and pH of the resulting infusate were examined. Selected drug solutions of various osmolalities and 5% dextrose and 0.2% sodium chloride injection or Ringer's injection, lactated, were administered simultaneously using a drug delivery system capable of controlling the flow rates independently. The i.v. fluid and drug infusion rates were varied from 4 to 46 and from 2 to 31 ml/hr, respectively. Osmolality, pH, and specific gravity of the drug solutions and final infusate were measured. Using alligation, the osmolality, pH, and specific gravity of the final infusate were calculated; correlations between observed and calculated values were computed. Guidelines for achieving an osmolality of the final infusate less than 500 mOsm/kg water were calculated. The observed and calculated osmolality and specific gravity of the final infusate were significantly correlated (r = 0.91, p less than 0.001, and r = 0.99, p less than 0.01, respectively). The pH of the final infusate was dependent on the pH of the original drug solution and was not affected by i.v. fluid and drug delivery flow rates. Osmolality may be an important factor to consider when establishing ideal drug solution infusion rates or concentrations. The infusate osmolality can be controlled by adjusting the concentration of the drug solution, drug infusion rate, or the i.v. fluid flow rate.

Hydrogen-Ion Concentration↗