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PubMed1982

Selection for high specific gravity of eggs in a flock of Australorp hens.

1. A realised heritability of 0.23 was obtained in an Australorp flock (S) selected for five generations for high egg specific gravity. 2. A comparison with an unselected control flock (C) over 50 weeks of lay in the final generation indicated a number of statistically significant correlated responses in commercially important traits in the S line in addition to the direct response of +0.004 in specific gravity. 3. With an increase in specific gravity, there was a decrease of 3.4 in the percentage of soft-shelled eggs laid. 4. The weight and albumen height of eggs measured within 1 hour of lay declined by 1.8 g and 2.1 Haugh units respectively. 5. There were reductions in the weight and albumen height losses of eggs stored over a 10-d period (C 0.74, S 0.62 g and C 17.9, S 15.0 Haugh units respectively), so that at the end of this period the albumen heights in both lines were the same. 6. Average body weight and daily food intake were less by 0.28 kg and 7.5 g respectively. 7. Although there was no change in egg production, the average age at first egg was reduced by 11.3 d.

Animals↗
PubMed1999

Measurement of specific gravity as a surrogate for urinary flow rate--a singular study.

About two hundred and fifty urine samples were collected some years ago in the course of experimental exposure of one individual to benzene vapor. Phenol concentrations and specific gravities were recorded, together with the volume of urine samples and the times of voiding. Review of this data shows that the reciprocal of specific gravity minus unity (SG-1) measured by refractometer correlated closely with urinary flow rate, while those using the traditional urinometer correlated much less closely. If this is valid for all workers, then refractometer measurement of specific gravity may be used as a surrogate for flow rate. More consistent interpretation of spot urine sampling results as a measure of intake of hazardous substances through occupational exposure is then possible. This is particularly the case if used in conjunction with the formula developed and tested by Araki et al. for flow rate adjustment.

Benzene↗
PubMed1982

Specific gravity adjustment of urine analysis results.

Analysis of urine samples for compounds such as lead, phenol, or 4,4'-methylene bis (2-chloroaniline) (MBOCA) are often adjusted for specific gravity following a recommendation in a NIOSH Benzene Criteria Document. The adjustment normalizes all results to a specific gravity of 1.024 by multiplying the analytical result in microgram/liter by 24/G where G is the last 2 digits of the specific gravity of the urine sample. The adjustment calculation is based on a suggestion by Levine and Fahy, who found that the urine solids content is roughly proportional to 24/G. We believe this adjustment to be inappropriate based on the following considerations.

Humans↗
PubMed2004

Isolation of cucumber CsARF cDNAs and expression of the corresponding mRNAs during gravity-regulated morphogenesis of cucumber seedlings.

Cucumber seedlings show positive gravitropism and bend in the transition zone between the hypocotyl and the root. The peg, a specialized protuberance, develops on the concave side of the bending transition zone. Auxin and the mRNA of an auxin-inducible gene (CsIAA1) isolated from cucumber are differentially accumulated across the transition zone during the gravity-regulated peg formation. In this study, five cDNAs of Auxin Response Factors (ARFs) from cucumber were isolated and their mRNA accumulation was compared with that of CsIAA1. The tissue specificity of CsARF2 mRNA accumulation was similar to that of CsIAA1. Because the structural character of CsARF2 predicts that it is a transcriptional activator, CsARF2 may be involved in the activation of CsIAA1 transcription, which plays a role in gravity-regulated peg formation. Neither gravity nor auxin affected mRNA accumulation of five CsARFs including CsARF2, suggesting that CsARF2 may be regulated at a post-transcriptional level to induce the asymmetric expression of the CsIAA1 gene in response to gravistimulation and auxin in cucumber seedlings.

Amino Acid Sequence↗
PubMed1977

Gravity-induced cell elongation.

When the flowering stalks of grasses are displaced from the vertical position they are caused to bend at special gravity perceptive regions, the nodes. Growth of the lower side of the node returns the shoot to its original orientation with respect to gravity, but when this is achieved, growth ceases. Possible mechanisms by which elongation growth is turned on in the lower sides and turned off again once the stalk is vertical are described. The facilities of Spacelab offer a unique opportunity for testing models of gravity perception and response.

Dose-Response Relationship, Drug↗
PubMed1987

The role of calcium ions in gravity signal perception and transduction.

Ca2+ is implicated as a messenger in coupling various environmental stimuli, such as gravity and light, to response. In recent years, it has become evident that Ca2+ plays a central role in all three phases of gravitropism--perception, transduction and response. The root cap, which is known to contain high amounts of Ca2+ and calmodulin, is the primary site of gravity perception. The possible role of phosphoinositide turnover and Ca(2+) - and Ca(2+) -calmodulin-dependent enzymes such as Ca(2+) -ATPase and protein kinases in gravitropism is discussed. A model is proposed to describe the role of Ca2+ in both normal and light-dependent gravity response in roots.

Calcium↗
PubMed1982

Specific gravity of brain tissue during maturation.

The water content of the brain is closely related to the maturation and degree of myelination. In control rats studied from the day of birth to the age of 26 days, brain specific gravity increased in parallel to the decrease in water content (r = 1.00). Rats treated with 6-hydroxydopamine (6-OHDA) 100 microns/g daily during the first 2 or 4 days of life had significantly lower specific gravity than controls in all parts of the brain at the age of 2 weeks. With the smaller dose 6-OHDA, the specific gravity at the age of 1 month was lower than in controls in the occipital cortex; with the larger dose it was significantly reduced in all cortical regions as well as in the pons and the diencephalon. 2-months old 6-OHDA treated rats did not differ from controls. Rats pretreated with desipramine 30 min before administration of 6-OHDA to prevent uptake of 6-OHDA into catecholaminergic neurons did not differ from controls. Neonatal 6-OHDA treatment affects predominantly noradrenergic terminals in the cerebral cortex with cell bodies in the locus coeruleus. The present results are consistent with the hypothesis that these neurons have a trophic influence on the brain development during the postnatal maturation.

Aging↗
PubMed1986

Changes in specific gravity as a sign of disturbed brain maturation in protein-deprived rats.

The specific gravity of the cerebral cortex of normal and protein-deprived rats aged 15, 21 and 25 days was determined. The increase in specific gravity seen in control rats in the course of their development was reduced in protein-deprived rats in the course of the period between 15 and 21 days of age. The results are in agreement with previous reports on delayed maturation of the brain in protein-deprived rats and indicate that determination of brain specific gravity may serve as a suitable screening method in situations when a disturbed brain maturation is suspected.

Animals↗
PubMed1979

A comparison of urinary specific gravity and osmolality in sheep.

Urinary specific gravity and osmolality were determined on urine samples collected from three categories of sheep -- animals that were normal, in diuresis or had nephron numbers reduced surgically. Values for specific gravity and osmolality were compared and regression coefficients calculated for each category of sheep. In this study, specific gravity was found to be a relatively reliable indicator of osmolality, the correlation being highest in the urine from the sheep with reduced nephron numbers.

Animals↗
PubMed1987

Correlation of specific gravity and osmolality of urine in neonates and adults.

There is good correlation between the specific gravity and osmolality of urine obtained from neonates and adults, if specimens contain neither protein nor glucose. The regression equations between specific gravity and osmolality, however, differ considerably between the two age groups, maturation to the adult regression occurring within the first 5 years of life. Specifically derived regression equations should therefore be used when predicting urine osmolality from measurement of specific gravity in neonates.

Adolescent↗
PubMed1973

Variation in plasma calcium with induced changes in plasma specific gravity, total protein, and albumin.

The relationship of plasma calcium levels to changes in plasma specific gravity, total protein, and albumin induced by venous stasis was investigated. Factors were derived for adjusting calcium results to offset the effects of variation in protein concentration and thus to make them of increased discriminatory value to the clinician. The validity of an existing specific gravity correction has been substantiated, but a more exact adjustment of 0.23 mg/100 ml of calcium for every 0.001 change in specific gravity is proposed. We recommend for automated laboratories that the factor based on albumin be used: 0.09 mg/100 ml of calcium should be subtracted from the total calcium value for every increase of 0.1 g in albumin above 4.6 g/100 ml, and a corresponding addition should be made for values of albumin below 4.6 g/100 ml.Using a calcium specific electrode, it has been shown that the ionized calcium concentration does not alter with prolonged venous stasis.

Adult↗
PubMedDate not supplied

Acute effect of angiographic contrast medium on cortical specific gravity after middle cerebral artery occlusion in rats.

Early angiography after cerebral arterial occlusion has been cited as potentially detrimental. This investigation evaluates the effect of acute angiographic contrast medium administration on the cortical edema induced by middle cerebral artery (MCA) occlusion. Sixteen rats underwent MCA occlusion, and after 1 hour half the rats underwent ipsilateral internal carotid injection of meglumine diatrizoate, whereas the remainder underwent cervical internal carotid exposure only. Six rats had only sham operations on the MCA and internal carotid, and 4 other rats served as normal controls. Cortical specific gravity was measured to reflect cerebral edema 4 hours after occlusion or sham operation. Specific gravity of the lateral frontal cortex in the hemisphere ipsilateral to occlusion was 1.0396 +/- 0.0011 (mean +/- SEM) when no angiographic contrast medium was administered, significantly less (p less than 0.01) than in rats exposed to contrast medium (specific gravity 1.0442 +/- 0.0005). The latter value was not significantly different from normal. Other cortical areas on the side of the contrast medium injection were also relatively dehydrated compared with normal controls. Early meglumine diatrizoate administration after MCA occlusion results in a decrease in cerebral cortical edema, possible by inducing an osmotic gradient that draws water from the extravascular space.

Animals↗
PubMed1983

Urine specific gravity measurements: comparison of a new reagent strip method with existing methodologies, as applied to the water concentration/dilution tests.

A study was carried out to compare a new, unique chemical strip test for the measurement of urine specific gravity with the traditional methods of hydrometry and refractometry, during water concentration/dilution tests in 12 normal subjects. The pattern of specific gravity results during these serial measurements was virtually identical for the strip and for the comparative methods. Comparison of the strip results with those obtained by both hydrometry and refractometry produced acceptable linear regression data. In addition, a close relationship was demonstrated between the strip specific gravity and urine osmolality. The findings show that the strip method is an acceptable alternative to traditional methods as an indicator of urine concentration.

Adult↗
PubMed2004

The measurement of solute diffusion coefficients in dilute liquid alloys: the influence of unit gravity and g-jitter on buoyancy convection.

Liquid diffusion experiments conducted on the MIR space station using the Canadian Space Agency QUELD II processing facility and the microgravity isolation mount (MIM) showed that g-jitter significantly increased the measured solute diffusion coefficients. In some experiments, milli-g forced vibration was superimposed on the sample when isolated from the ambient g-jitter; this resulted in markedly increased solute transport. To further explore the effects arising in these long capillary diffusion couples from the absence of unit-gravity and the presence of the forced g-jitter, the effects of a 1 milli-g forcing vibration on the mass transport in a 1.5 mm diameter long capillary diffusion couple have been simulated. In addition, to increase understanding of the role of unit gravity in determining the extent to which gravity can influence measured diffusion coefficient values, comparative experiments involving gold, silver, and antimony diffusing in liquid lead have been carried out using a similar QUELD II facility to that employed in the QUELD II/MIM/MIR campaign but under terrestrial conditions. It was found that buoyancy-driven convection may still persist in the liquid even when conditions are arranged for a continuously decreasing density gradient up the axis of a vertical long capillary diffusion couple due to the presence of small radial temperature gradients.

Acceleration↗
PubMed1979

Correlation of absorption coefficients with intracranial fluid protein concentrations and specific gravities.

Samples of ventricular cerebrospinal fluid, tumor cyst fluid, and subdural fluid were obtained from 30 patients at operation. The protein concentration and the specific gravity of each sample were measured and the corresponding mean absorption numbers were calculated from the numerical printout of the preoperative computerized tomogram. For fluids with a specific gravity greater than 1.005, a linear relationship was demonstrated between protein concentration and specific gravity. For protein concentrations greater than 300 mg/dl, there was a linear relationship between protein concentration and the mean absorption number. As the precision of present instrumentation improves, it is expected that a noninvasive technique for estimating intracranial protein concentration will have a number of clinical application.

Absorption↗
PubMed1995

Physiological tremor under pseudo-fraction gravity.

The effect of pseudo-fraction gravity on physiological tremor of the human finger (finger tremor) has been examined experimentally by immersing an index finger into water at different immersion levels. The pseudo-fraction gravity, gamma G, was established by water buoyancy at immersion level omega, G being gravitation acceleration and gamma between zero and unit. The nature of variations of finger tremor under the influence of gamma G is estimated based on FFT spectral analysis. It is illustrated that with a decrease in gamma, or equivalently an increase in omega, two dominant peaks remaining approximately constant in frequencies around 10Hz and 20Hz are found, while peak amplitude is decreased rapidly for higher peak and slowly for lower one. Theoretically the effect of pseudo-fraction gravity is analyzed in terms of a specific model for finger tremor. The experimental results presented in this paper are predicted rather well by two resonant modes which occurred in our model system. It is possible to conclude that the model, which is characterized by a pair of antagonistic muscles and two reflex pathways, provides an adequate quantitative description of finger tremor.

Adult↗
PubMed2000

[Woody plant and gravity].

In this review, we attempted to summarize the effect of gravity on growth of woody plants, broad leaved trees, on earth. It is well known that in tilted broad leaved trees, tension wood formed in the secondary xylem causes negative gravitropism. Gibberellin has been shown to induce tension wood in weeping branch, causing its upright growth. Recent study has shown that seedling of Japanese cherry tree grown on three dimensional clinostat, a device that simulates microgravity, grew at random angles, and that the formation of secondary xylem, as supporting tissue for upright growth, decreased. In the decreased xylem formation, the inhibition of the differentiation and development of fiber cell was clearly observed. These results suggest that in attitude control and morphogenesis of stem in woody plant, secondary xylem formation seriously relates to gravity on earth. In woody plant, the mechanism of gravity perception and the following signal transduction have not yet been elucidated, although the recent study reported the possibility that endodermal starch sheath cells and plant hormones may play some role in the mechanism. Space experiment for woody plant is expected to study these problem.

Biomechanical Phenomena↗
PubMed1994

Vector-averaged gravity does not alter acetylcholine receptor single channel properties.

To examine the physiological sensitivity of membrane receptors to altered gravity, we examined the single channel properties of the acetylcholine receptor (AChR), in co-cultures of Xenopus myocytes and neurons, to vector-averaged gravity in the clinostat. This experimental paradigm produces an environment in which, from the cell's perspective, the gravitational vector is "nulled" by continuous averaging. In that respect, the clinostat simulates one aspect of space microgravity where the gravity force is greatly reduced. After clinorotation, the AChR channel mean open-time and conductance were statistically not different from control values but showed a rotation-dependent trend that suggests a process of cellular adaptation to clinorotation. These findings therefore suggest that the ACHR channel function may not be affected in the microgravity of space despite changes in the receptor's cellular organization.

Acetylcholine↗