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At least 595 records · Page 33Linked to original sources
PubMed2003

The ARG1-LIKE2 gene of Arabidopsis functions in a gravity signal transduction pathway that is genetically distinct from the PGM pathway.

The arl2 mutants of Arabidopsis display altered root and hypocotyl gravitropism, whereas their inflorescence stems are fully gravitropic. Interestingly, mutant roots respond like the wild type to phytohormones and an inhibitor of polar auxin transport. Also, their cap columella cells accumulate starch similarly to wild-type cells, and mutant hypocotyls display strong phototropic responses to lateral light stimulation. The ARL2 gene encodes a DnaJ-like protein similar to ARG1, another protein previously implicated in gravity signal transduction in Arabidopsis seedlings. ARL2 is expressed at low levels in all organs of seedlings and plants. arl2-1 arg1-2 double mutant roots display kinetics of gravitropism similar to those of single mutants. However, double mutants carrying both arl2-1 and pgm-1 (a mutation in the starch-biosynthetic gene PHOSPHOGLUCOMUTASE) at the homozygous state display a more pronounced root gravitropic defect than the single mutants. On the other hand, seedlings with a null mutation in ARL1, a paralog of ARG1 and ARL2, behave similarly to the wild type in gravitropism and other related assays. Taken together, the results suggest that ARG1 and ARL2 function in the same gravity signal transduction pathway in the hypocotyl and root of Arabidopsis seedlings, distinct from the pathway involving PGM.

Amino Acid Sequence↗
PubMed1990

Relationships of total protein, specific gravity, viscosity, refractive index and latex agglutination to immunoglobulin G concentration in mare colostrum.

A colostrum sample was collected within 24 h after foaling from 27 mares and from 10 other mares a milk sample was collected several weeks post partum. Immunoglobulin G concentrations were determined quantitatively by radial immunodiffusion and semi-quantitatively using a commercial latex agglutination test. Total protein, specific gravity, viscosity and refractive index were determined and their relationships to the immunoglobulin G concentration analysed. All parameters correlated with the immunoglobulin G concentration. The latex agglutination test divided the colostrum samples into three groups with different means for immunoglobulin G and total protein concentrations. Specific gravity and the latex agglutination test were found to be the methods best suited for on-farm evaluation of colostrum quality.

Animals↗
PubMed1980

Serial measurements of CT attenuation and specific gravity in experimental cerebral edema.

Vasogenic cerebral edema was induced cryogenically in rhesus monkeys. Serial scans in both axial and coronal planes were used to study the onset, peak, and regression of edema. Progression of edema, predominantly involving the white matter, was analyzed from the postmortem distribution of a blood/brain barrier indicator (Evans blue) injected at surgery. Specific gravity was measured in fresh, unfixed specimens from both the edematous and normal hemispheres and correlated with corresponding CT attenuation values obtained before death. The drop in specific gravity closely corresponded to the decrease in CT attenuation.

Animals↗
PubMed2004

Effect of changing the gravity vector on respiratory output and control.

We studied the respiratory output in five subjects exposed to parabolic flights [gravity vector 1, 1.8 and 0 gravity vector in the craniocaudal direction (Gz)] and when switching from sitting to supine (legs bent at the knees). Despite differences in total respiratory compliance (highest at 0 Gz and in supine and minimum at 1.8 Gz), no significant changes in elastic inspiratory work were observed in the various conditions, except when comparing 1.8 Gz with 1 Gz (subjects were in the seated position in all circumstances), although the elastic work had an inverse relationship with total respiratory compliance that was highest at 0 Gz and in supine posture and minimum at 1.8 Gz. Relative to 1 Gz, lung resistance (airways plus lung tissue) increased significantly by 52% in the supine but slightly decreased at 0 Gz. We calculated, for each condition, the tidal volume changes based on the energy available in the preceding phase and concluded that an increase in inspiratory muscle output occurs when respiratory load increases (e.g., going from 0 to 1.8 Gz), whereas a decrease occurs in the opposite case (e.g., from 1.8 to 0 Gz). Despite these immediate changes, ventilation increased, going to 1.8 and 0 Gz (up to approximately 23%), reflecting an increase in mean inspiratory flow rate, tidal volume, and respiratory frequency, while ventilation decreased (approximately -14%), shifting to supine posture (transition time approximately 15 s). These data suggest a remarkable feature in the mechanical arrangement of the respiratory system such that it can maintain the ventilatory output with small changes in inspiratory muscle work in face of considerable changes in configuration and mechanical properties.

Acceleration↗
PubMed2000

Properties of the internal representation of gravity inferred from spatial-direction and body-tilt estimates.

One of the key questions in spatial perception is whether the brain has a common representation of gravity that is generally accessible for various perceptual orientation tasks. To evaluate this idea, we compared the ability of six tilted subjects to indicate earth-centric directions in the dark with a visual and an oculomotor paradigm and to estimate their body tilt relative to gravity. Subjective earth-horizontal and -vertical data were collected, either by adjusting a visual line or by making saccades, at 37 roll-tilt angles across the entire range. These spatial perception responses and the associated body-tilt estimates were subjected to a principal-component analysis to describe their tilt dependence. This analysis allowed us to separate systematic and random errors in performance, to disentangle the effects of task (horizontal vs. vertical) and paradigm (visual vs. oculomotor) in the space-perception data, and to compare the veridicality of space perception and the sense of self-tilt. In all spatial-orientation tests, whether involving space-perception or body-tilt judgments, subjects made considerable systematic errors which mostly betrayed tilt underestimation [Aubert effect (A effect)] and peaked near 130 degrees tilt. However, the A effect was much smaller in body-tilt estimates than in spatial pointing, implying that the underlying signal processing must have been different. Pointing results obtained with the visual and the oculomotor paradigm were not identical either, but these differences, which were task-related (horizontal vs. vertical), were subtle in comparison. The tilt-dependent pattern of random errors (noisy scatter) was almost identical in visual and oculomotor pointing results, showing a steep monotonic increase with tilt angle, but was again clearly different in the body-tilt estimates. These findings are discussed in the context of a conceptual model in an attempt to explain how the different patterns of systematic and random errors in external-space and self-tilt perception may come about. The scheme proposes that basically similar computational mechanisms, working with different settings, may be responsible.

Adult↗
PubMedDate not supplied

Screening for microalbuminuria simplified by urine specific gravity.

BACKGROUND: The albumin-to-creatinine ratio and the 24-hour urine collection to measure microalbuminuria are inconvenient and expensive. The newer rapid and less expensive dipstick methods for screening of microalbuminuria estimate only albumin and are subject to errors caused by variation in volume. We determined the relation between urine-specific gravity (Usg) and urine creatinine (Ucr) so that Ucr can be derived from Usg to correct for albumin concentration in the urine which is influenced by urine volume. METHODS: We randomly included 42 consecutive patients from the primary care clinic, and 34 patients from the diabetic clinic. RESULTS: We found that a very good correlation existed between Usg and Ucr in the 42 patients from the primary care clinic (Ucr = 11.4 x Usg -11,509, r = 0.83, p < 0.001). Patients from the diabetic clinic who had well-controlled blood sugar (n = 21) showed a similar trend (Ucr = 10.82 x Usg -10,882, r = 0.87, p < 0.001). However, this was not the case with uncontrolled diabetics (Ucr = 2.53 x Usg -2,513, r = 0.26, NS). Using simple arithmetic, we derived a simplified formula where Ucr can be predicted from Usg. Using multiple regression to incorporate the urinary glucose level by dipstick, a more generic formula was obtained for estimating urinary creatinine. CONCLUSION: Usg can be used instead of Ucr to normalize for the varied urine concentration while screening for microalbuminuria. Poorly controlled diabetics should be screened after their blood sugars are well controlled or use the more generic formula that incorporates urinary glucose. Thus, by measuring spot urine albumin and specific gravity by dipsticks one gets an easy, immediate and accurate estimation of microalbuminuria in an office setting.

Albuminuria↗
PubMed1996

Centre of gravity of the body during the ontogeny of chimpanzee bipedal walking.

Bipedal walking was studied in chimpanzees between 1 and 19 years of age by measuring the external energy generated by the movement of the centre of gravity of the body. The 'recovery' of external energy in infant chimpanzees less than five years of age is smaller than in juveniles from 5 to 19 years of age. During the single stance phase, the short, flexed hindlimb of chimpanzees younger than 5 years is not able to lift the body centre of gravity high enough, so that these infants have a considerable energy output during bipedal walking. Extension of the hindlimb is one of the bases for energy economy in human bipedalism. The development of this low-energy-cost mechanism is an important component of the evolution of human bipedalism.

Aging↗
PubMed1994

Specific gravities of desflurane, enflurane, halothane, isoflurane, and sevoflurane.

We determined the specific gravities of presently available volatile anesthetics in order to supply a consistent quantitative basis for calibration standards. Using four 50-mL volumetric flasks, we obtained the following values at 20 degrees C: desflurane 1.4651 +/- 0.0004 g/mL (mean +/- SD); enflurane 1.5230 +/- 0.0003 g/mL; halothane 1.8680 +/- 0.0007 g/mL; isoflurane 1.5019 +/- 0.0006 g/mL; and sevoflurane 1.5203 +/- 0.0008 g/mL. Measurements made at 0 degree C, 10 degrees C, 20 degrees C, and 25 degrees C (not for desflurane at 25 degrees C) revealed a decrease in specific gravity of 0.00250 +/- 0.00014 g/mL for each degree of increase in temperature. These data bear on the issue of cost for anesthetics that are stored as liquids, but used as gases.

Anesthesia, Inhalation↗
PubMed1998

Determining specific gravity, specific heat, and surface area of rabbits for a possible thermodynamic approach to body temperature change.

In order to investigate the mechanisms of body temperature change from a thermodynamic aspect, we investigated the specific gravity, specific heat and surface area of rabbit in situ. We obtained the following results. 1. The specific gravity of normal, shorn and ecdysed rabbits is 0.94, 0.95 and 0.97, respectively. 2. The specific heat of normal, shorn and ecdysed rabbits is 0.95, 0.89 and 0.69 cal/g.K, [corrected] respectively. 3. The surface area of the rabbit was also measured by using the weight of aluminum foil which covered the surface.

Animals↗
PubMed1992

Color Doppler sonography of ureteral jets in normal volunteers: importance of the relative specific gravity of urine in the ureter and bladder.

OBJECTIVE: Sonographic visualization of ureteral jets is a well-recognized phenomenon. In vitro studies have indicated that detection of fluid flow similar to ureteral jets depends on differences in density between the moving and the stationary fluid. This study was undertaken to determine if differences in density between ureteral urine and urine in the bladder could make a significant impact on the sonographic detectability of ureteral jets in vivo. SUBJECTS AND METHODS: Ten healthy volunteers were vigorously hydrated after an overnight fast. An initial color Doppler sonographic examination of ureteral jets was performed before voiding (while concentrated urine that had accumulated overnight was still in the bladder). A second examination was performed after two cycles of voiding and refilling the bladder (to ensure that dilute urine produced by the hydration was in the bladder). RESULTS: In all subjects, normal ureteral jets were readily identified on the initial examination. The difference in the estimated specific gravity between bladder urine and ureteral urine during the initial examination ranged from 0.002 to 0.016 (mean, 0.008). This was a statistically significant difference (p less than .05). On the second examination, ureteral jets were not detected from either ureter in any subject. The difference in the estimated specific gravity of bladder urine and ureteral urine during the second examination ranged from 0.000 to 0.002 (mean, 0.001). This was not a statistically significant difference (p greater than .05). There was no statistically significant difference in the diuresis rates throughout the course of the examinations. These ranged from 300 to 1218 ml/hr. CONCLUSION: These in vivo results support the hypothesis that detection of ureteral jets depends on density differences between ureteral and bladder urine. This is important clinically, because normal ureteral jets may be undetectable, despite adequate hydration and high rates of diuresis, if the patient is allowed to completely void and refill the bladder before the examination.

Adult↗
PubMed1989

The use of bioelectric currents to study gravity perception in roots.

Inhibitor-based studies of gravity perception in plants have yielded ambiguous results because gravitropism consists of many steps in series. Inhibiting any step eliminates gravicurvature; it cannot be shown whether gravity perception and transduction are affected by the inhibitory treatment. The use of the vibrating probe has allowed detection of a response that is measurable independent of stimulus transmission and growth, two post-transduction steps of gravitropism. This application of the vibrating probe requires particular attention to artifacts. Calmodulin action and auxin transport are both believed to be components of gravitropism and specific roles have been proposed for them in graviperception. The perception-dependent current measured with the vibrating probe is eliminated by inhibitors of calmodulin, but not by auxin inhibitors. Thus, the vibrating probe has made it possible to offer more direct evidence for a role of calmodulin in transduction, and to reject one for auxin transport in perception and transduction.

Biological Transport↗
PubMed2003

Effects of storage time and temperature on pH, specific gravity, and crystal formation in urine samples from dogs and cats.

OBJECTIVE: To determine effects of storage temperature and time on pH and specific gravity of and number and size of crystals in urine samples from dogs and cats. DESIGN: Randomized complete block design. ANIMALS: 31 dogs and 8 cats. PROCEDURE: Aliquots of each urine sample were analyzed within 60 minutes of collection or after storage at room or refrigeration temperatures (20 vs 6 degrees C [68 vs 43 degrees F]) for 6 or 24 hours. RESULTS: Crystals formed in samples from 11 of 39 (28%) animals. Calcium oxalate (CaOx) crystals formed in vitro in samples from 1 cat and 8 dogs. Magnesium ammonium phosphate (MAP) crystals formed in vitro in samples from 2 dogs. Compared with aliquots stored at room temperature, refrigeration increased the number and size of crystals that formed in vitro; however, the increase in number and size of MAP crystals in stored urine samples was not significant. Increased storage time and decreased storage temperature were associated with a significant increase in number of CaOx crystals formed. Greater numbers of crystals formed in urine aliquots stored for 24 hours than in aliquots stored for 6 hours. Storage time and temperature did not have a significant effect on pH or specific gravity. CONCLUSIONS AND CLINICAL RELEVANCE: Urine samples should be analyzed within 60 minutes of collection to minimize temperature- and time-dependent effects on in vitro crystal formation. Presence of crystals observed in stored samples should be validated by reevaluation of fresh urine.

Animals↗
PubMed1992

Effect of microbial fermentation on functional specific gravity of small forage particles.

Two experiments were designed to determine the effect of gas production during in vitro digestion on functional specific gravity (FSG) of forage particles. In Exp. 1, FSG of ground alfalfa hay decreased from 1.123 to 1.049 between 3 and 9 h of incubation and increased thereafter to reach a plateau at 1.309 after 30 h of incubation. Gas production peaked at 6 h, but gas associated with particles increased until 9 h of incubation. Gas associated with solid residue was correlated to gas production (r = -.67) but also was influenced by gas holding capacity and rate of escape from the particles. In Exp. 2, measurements were performed on ground alfalfa hay, alfalfa silage, and bromegrass hay containing 42.6, 35, and 66.4% NDF, respectively. Gas production seemed to be related to the amount of readily available substrate. Although at 9 h of incubation more gas was produced by alfalfa silage (.235 mL.min-1.g of DM-1) than by bromegrass hay and alfalfa hay (.087 and .187 mL.min-1.g of DM-1, respectively), gas associated with particles was greater for alfalfa hay (.416 mL/g of DM) than for bromegrass hay and alfalfa silage (.256 and .281 mL/g of DM, respectively). The increase in FSG was more rapid for alfalfa silage than for the hays. After 27 h of digestion, gas associated with particles (milliliters per gram of DM) and FSG were .164, 1.226; .147, 1.235; and .001, 1.467 for bromegrass hay, alfalfa hay, and alfalfa silage, respectively. Gas produced during fermentation delayed the increase in specific gravity of forage particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1978

Shell gland oxygen consumption in hens producing eggs of low or high specific gravity.

Oxygen consumption of shell gland lumenal tissue was found to be higher in hens producing eggs of high specific gravity (greater than or equal to 1.080) when compared to tissue from hens producing eggs of low specific gravity (less than or equal to 1.075). Shell gland lumenal tissue oxygen consumption was also greater when an egg was in the shell gland as compared to hens with an egg in the magnum (9.8 and 8.0 microliter O2/hr/mg tissue respectively).

Animals↗
PubMed1988

Rapid determination of egg weight and specific gravity using a computerized data collection system.

A rapid data-collection system for determining egg weight and specific gravity is described. The method links a microcomputer and an electronic balance to facilitate specific gravity determination by the displaced water (CADW) or Archimedes' method. Measurements obtained by this technique were compared with those determined by the saline flotation method. Repeatability measures showed both methods to be relatively precise. The CADW method was faster and reduced opportunities for clerical error.

Animals↗
PubMed1991

Specific gravity of eggs and eggshell weight from commercial layers and broiler breeders in relation to time of oviposition.

Eggs were collected from 1 day of production of Hy-Line W36 commercial egg production hens 55 wk old. Also, eggs were collected from 1 day of production of Arbor Acres broiler breeder hens when they were 40 and 55 wk of age. The eggs were immediately weighed (EW) after collection and specific gravity (ESG) determined. The eggs were then broken and the contents removed. Shells were washed, air dried, and weighed. The weights of shells (ESW) were calculated using the following formulas: Broiler breeder ESW = 1.9128 x EW - 1.9741 EW/ESG and layer ESW = 1.9140 EW - 1.9754 EW/ESG. Shell density (ESD) was calculated using a modification of this formula. Egg weights of both commercial layers and broiler breeders were heaviest in the early morning. There was a steady decline in EW until 1545 h; EW increased thereafter. Specific gravity of eggs was highest in the morning, declined until 1245 h, and then increased thereafter. Shell weight was also highest in the morning, declined until 1245 h, and then increased thereafter. The calculated and measured ESW were highly correlated. The ESD was 2.147 and 2.160 for the commercial layers and broiler breeders, respectively.

Animals↗
PubMed2001

Stereopsis outweighs gravity in the control of the eyes.

The eyes are controlled by multiple brain circuits, some phylogenetically old and some new, whose aims may conflict. Old otolith reflexes counterroll the eyes when the head tilts relative to gravity. Newer vergence mechanisms coordinate the eyes to aid stereoptic vision. We show that counterroll hinders stereopsis, weakly when you look into the distance but strongly when you look near. The resolution of this conflict is that counterroll virtually vanishes when monkeys look close, i.e., stereopsis overrides gravity-driven reflexes but only on near gaze. This balance between gyroscopic and stereoptic mechanisms explains many other puzzling features of primate gaze control, such as the weakness of our otolith-ocular reflexes even during far viewing and the strange geometry of the primate counterpitch reflex, which rolls the eyes clockwise when monkeys look leftward while their heads are tipped nose up, but rolls them counterclockwise when the monkeys look rightward, and reverses this pattern when the head is tipped nose down.

Animals↗
PubMed1990

Gravity-induced changes in intracellular potentials in elongating cortical cells of mung bean roots.

Gravity-induced changes in intracellular potentials in primary roots of 2-day-old mung bean (Vigna mungo L. cv. black matpe) seedlings were investigated using glass microelectrodes held by 3-dimensional hydraulic micro-drives. The electrodes were inserted into outer cortical cells within the elongation zone. Intracellular potentials, angle of root orientation with respect to gravity, and position within the root of the impaled cortical cell were measured simultaneously. Gravistimulation caused intracellular potential changes in cortical cells of the elongation zone. When the roots were oriented vertically, the intracellular potentials of the outer cortical cells (2 mm behind the root apex) were approximately - 115 mV. When the roots were placed horizontally cortical cells on the upper side hyperpolarized to - 154 mV within 30 s while cortical cells on the lower side depolarized to about - 62 mV. This electrical asymmetry did not occur in cells of the maturation zone. Because attempts to insert the electrode into cells of the root cap were unsuccessful, these cells were not measured. The hyperpolarization of cortical cells on the upper side was greatly reduced upon application of N,N'-dicyclohexylcarbodiimide (DCCD), an inhibitor of respiratory energy coupling. When stimulated roots were returned to the vertical, the degree of hyperpolarization of cortical cells on the previous upper side decreased within 30 s and approached that of cortical cells in non-stimulated roots. This cycle of hyperpolarization/loss of hyperpolarization was repeatable at least ten times by alternately turning the root from the vertical to the horizontal and back again. The very short (<30 s) lag period of these electrical changes indicates that they may result from stimulus-perception and transduction within the elongation zone rather than from transmission of a signal from the root cap.

Cell Differentiation↗