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PubMed1995

Plasma specific gravity for identifying hypovolaemia.

To define ranges of plasma specific gravity useful for identifying volume depletion in older adults, plasma specific gravity was measured in 170 young adults (mean age 28 years) and 100 retirees (mean age 81 years), and ranges of values likely to be associated with volume depletion were defined. Subsequently, measurements of plasma specific gravity were made in 68 older emergency room (ER) patients (mean age 74 years), a few of whom had obvious reasons for being hypovolaemic, e.g. dehydrating diarrhoea, and these results were compared to those for the control groups. Ranges for plasma specific gravity useful for identifying volume depletion were designated as possible hypovolaemia (1.0265-1.0279), probable hypovolaemia (1.0280-1.0294), and hypovolaemia (> or = 1.0295). Using these definitions, there were more older ER patients compared to both young and old control group subjects, respectively, with probable hypovolaemia (21% vs. 5% and 8%; p < 0.03) and hypovolaemia (16% vs. 0% and 0%; p < 0.03). This study establishes ranges for plasma specific gravity for young and old adults likely to be associated with hypovolaemia, and shows that based upon measurement of plasma specific gravity, older ER patients may often be hypovolemic even in the absence of obvious fluid-wasting illnesses. Future studies are needed to identify the risk factors for hypovolaemia in ER patients, and more vigorously substantiate the findings of this study.

Adult↗

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↗

PubMed1984

Assessment of a solid-phase reagent for urinary specific gravity determination.

We have compared the specific gravity (S.G.) determined by the N-Multistix method with that obtained from the Total Solids (TS) meter. Overall, 88.7% of the specific gravity results obtained with the reagent strip method were within 0.005 of those obtained with the TS meter. There was a good correlation between the methods and there was no bias for the group means obtained by either method. A good correlation was also found between the S.G. on the strip and osmolality (correlation coefficient of 0.955). The results obtained with the reagent strip for urinary specific gravity therefore appear acceptable for routine laboratory purposes.

Freezing↗

PubMed2001

Factors associated with colostral specific gravity in dairy cows.

The objectives of this study were to identify factors associated with colostral specific gravity in dairy cows, as measured by a commercially available hydrometer (Colostrometer). Colostral specific gravity was measured in 1085 first-milking colostrum samples from 608 dairy cows of four breeds on a single farm during a 5-yr period. Effects of breed, lactation number, and month and year of calving on colostral specific gravity were determined, as were correlations between colostral specific gravity, nonlactating period length, and 305-d yields of milk, protein, and fat. For 75 multiparous Holstein cows, relationships between colostral specific gravity, colostral IgG1, protein, and fat concentrations, and season of calving were determined. Colostral specific gravity values were lower for Brown Swiss and Ayrshire cows than for Jersey and Holstein cows, and lower for cows entering first or second lactation than third or later lactations. Month of calving markedly affected colostral specific gravity values, with highest values occurring in autumn and lowest values in summer. In multiparous Holstein cows, colostral specific gravity was more strongly correlated with colostral protein concentration (r = 0.76) than IgG1 concentration (r = 0.53), and colostral protein concentration varied seasonally (higher in autumn than summer). Our results demonstrate that colostral specific gravity more closely reflects colostral protein concentration than IgG1 concentration and is markedly influenced by month of calving. These results highlight potential limitations of using colostral specific gravity as an indicator of IgG1 concentration.

Animals↗

PubMed2002

The relationship between urine osmolality and specific gravity.

BACKGROUND: In general, there is a good correlation between the specific gravity and osmolality of a urine sample. In certain clinical conditions, such as uncontrolled diabetes mellitus, nephrotic syndrome, after the administration of intravenous radiocontrast material or saline diuresis, dependence upon specific gravity for determining the concentrating ability will result in over- or underestimation. METHODS: We studied the relationship between specific gravity and osmolality in vitro with simulated urines of varying composition. Urine samples from patients with different clinical conditions were also analyzed. RESULTS: The in vitro curves for sodium chloride, urea, creatinine, glucose, contrast dye, and albumin were plotted (specific gravity versus osmolality). We found a linear correlation between the specific gravity and osmolality of the 6 substances that were studied and for their combinations. The urine samples obtained from patients with different clinical conditions documented that reliance on specific gravity could over- or underestimate the urine osmolality. CONCLUSIONS: We concluded that in those clinical conditions, urine osmolality should always be determined and it should not be estimated based on specific gravity.

Humans↗

PubMed2003

Does canopy position affect wood specific gravity in temperate forest trees?

The radial increases in wood specific gravity known in many tree species have been interpreted as providing mechanical support in response to the stresses associated with wind loading. This interpretation leads to the hypothesis that individuals reaching the canopy should (1) be more likely to have radial increases in specific gravity and (2) exhibit greater increases than individuals in the subcanopy. Wood specific gravity was determined for three species of forest trees (Acer rubrum, Fagus grandifolia and Tsuga canadensis) growing in central Massachusetts, USA. Acer rubrum shows radial increases in specific gravity, but these increases are not more pronounced in canopy trees; the other two species show a pattern of radial decreases. The degree of radial increase or decrease is influenced by tree height and diameter. Of the dominant tree species for which we have data, A. rubrum, Betula papyrifera and Pinus strobus show radial increases in specific gravity, whereas F. grandifolia, T. canadensis and Quercus rubra show decreases. The occurrence of radial increases in B. papyrifera and P. strobus, which are often canopy emergents, suggests that it is overall adaptive strategy that is important rather than position (canopy vs. subcanopy) of any individual tree. It is suggested that radial increases in specific gravity are associated with early-successional status or characteristics and decreases with late-successional status or persistence in mature forest.

Acer↗

PubMed1993

Assessment of urine specific gravity by reagent strip test in newborn infants.

Specific gravity was measured with a strip test (N-Labstix SG, Ames Division, Miles, Puteaux, France) in 98 urine specimens obtained from 57 newborn infants; osmolality was measured with an osmometer. The strip test did not accurately predict urine osmolalities; a very weak correlation was found between the specific gravity and the osmolality (r2 = 0.598, P < 0.01). Specific gravity values up to 1.015 always indicated hypotonic urine with osmolality less than 211 mosmol/kg H2O, whereas higher values could be associated with either hypotonic or hypertonic urine. Therefore, the strip test cannot be recommended in the neonatal period because its clinical usefulness is strictly restricted to urine samples with low specific gravities (< or = 1.015) and without confounding variables (urine pH > or = 6.5, glucosuria, proteinuria, haematuria).

Hematuria↗

PubMed2003

Gravity-specific adaptation of the angular vestibuloocular reflex: dependence on head orientation with regard to gravity.

The gain of the vertical angular vestibuloocular reflex (aVOR) was adaptively altered by visual-vestibular mismatch during rotation about an interaural axis, using steps of velocity in three head orientations: upright, left-side down, and right-side down. Gains were decreased by rotating the animal and visual surround in the same direction and increased by visual and surround rotation in opposite directions. Gains were adapted in one head position (single-state adaptation) or decreased with one side down and increased with the other side down (dual-state adaptation). Animals were tested in darkness using sinusoidal rotation at 0.5 Hz about an interaural axis that was tilted from horizontal to vertical. They were also sinusoidally oscillated from 0.5 to 4 Hz about a spatial vertical axis in static tilt positions from yaw to pitch. After both single- and dual-state adaptation, gain changes were maximal when the monkeys were in the position in which the gain had been adapted, and the gain changes progressively declined as the head was tilted away from that position. We call this gravity-specific aVOR gain adaptation. The spatial distribution of the specific aVOR gain changes could be represented by a cosine function that was superimposed on a bias level, which we called gravity-independent gain adaptation. Maximal gravity-specific gain changes were produced by 2-4 h of adaptation for both single- and dual-state adaptations, and changes in gain were similar at all test frequencies. When adapted while upright, the magnitude and distribution of the gravity-specific adaptation was comparable to that when animals were adapted in side-down positions. Single-state adaptation also produced gain changes that were independent of head position re gravity particularly in association with gain reduction. There was no bias after dual-state adaptation. With this difference, fits to data obtained by altering the gain in separate sessions predicted the modulations in gain obtained from dual-state adaptations. These data show that the vertical aVOR gain changes dependent on head position with regard to gravity are continuous functions of head tilt, whose spatial phase depends on the position in which the gain was adapted. From their different characteristics, it is likely that gravity-specific and gravity-independent adaptive changes in gain are produced by separate neural processes. These data demonstrate that head orientation to gravity plays an important role in both orienting and tuning the gain of the vertical aVOR.

Adaptation, Physiological↗

PubMed2001

Adjustment to concentration-dilution of spot urine samples: correlation between specific gravity and creatinine.

OBJECTIVE: Spot urine samples were investigated to determine correlations between urinary creatinine and specific gravity, and intra- and inter-day variations other than gender- and age-dependence of urinary concentrations. METHODS: Urinary creatinine concentrations and specific gravity were determined in 534 spot samples (385 from men and 149 from women). Subjects' ages ranged between 18 and 68 years. Spot urine samples were also collected from 14 male subjects before and after a 1-week work-shift for the evaluation of intra- and inter-day variations of creatinine and specific gravity. RESULTS: In spot samples, creatinine concentrations ranged between 0.16 and 4.36 g/l and specific gravity between 1.002 and 1.037. A high correlation (r = 0.82, P < 0.001) was observed between creatinine and specific gravity; male subjects showed significantly higher values of creatinine (P < 0.001) than did female subjects (1.90 +/- 0.74 and 1.41 +/- 0.72 g/l, respectively) and specific gravity (1.023 +/- 0.006 and 1.020 +/- 0.007, respectively). In addition, creatinine but not specific gravity significantly decreased (P < 0.02) in subjects older than 50 years, compared with those under 40. CONCLUSIONS: Results confirm the gender-dependence of creatinine concentrations in spot specimens and also show age-dependence, indicating the need for these aspects to be considered when the range of acceptable samples is to be set. No significant intra- or inter-day variations were observed for the two parameters. Lastly, the possibility of a comparison of differently adjusted values was indicated by a conversion formula derived from adjustments to creatinine and the corresponding specific gravity of a hypothetical urinary value, as follows: specific gravity adjusted values = 1.48 x creatinine adjusted values.

Adolescent↗

PubMedDate not supplied

A comparison of reagent strips and the refractometer for measurement of urine specific gravity in hospitalized children.

Pediatric nurses in acute care settings routinely test urine for specific gravity, pH, glucose, protein, and other substances. In one tertiary care facility, nurses used the refractometer to test urine specific gravity and the reagent strip to test for other substances. This study was designed to provide data to determine if the reagent strip and the refractometer were interchangeable for measuring urine specific gravity in pediatric clients. Nurses obtained urine for specific gravity testing in 157 pediatric patients ranging in age from 1 day to 16 years. Each urine specimen was tested twice, once using the refractometer and once with the reagent strip. A Bland-Altman plot was used to determine the extent of agreement between the two measurement methods. The plot showed strong agreement between the two methods across a wide range of values for urine specific gravity. As a result of this study, staff nurses decided to use the reagent strip for urine specific gravity when other urine tests are needed and to use the refractometer when only a specific gravity is needed. This decision has resulted in a time savings for nurses who now do not have to repeat a reagent strip measurement. The decision also resulted in a savings of approximately $1200 in purchase of new refractometers for a newly constructed unit.

Adolescent↗

PubMed2005

Impacts of viability and purification on the specific gravity of Cryptosporidium oocysts.

The specific gravity of unpurified and purified Cryptosporidium oocysts was measured using an isopycnic gradient centrifugation technique. Specific gravity varied depending on the viability of the oocysts, as defined by permeabilty to 4',6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI), the presence or absence of internal structures, and whether or not oocysts were purified. The modal range of densities for a population of 1.4-week-old unpurified oocysts, was 1070-1073 kg/m3. This range was higher than that determined for 14-week-old purified oocysts, 1067-1070 kg/m3. Eleven- and 12-week-old unpurified populations exhibited a bimodal distribution of densities, with densities most frequently in the 1005-1041 and in the 1077-1108 kg/m3 range. In these populations, a high percentage of the oocysts having densities greater than 1077 kg/m3 were viable, while oocysts in the 1005-1024 kg/m3 range were predominately nonintact, and oocysts in the 1024-1041 kg/m3 range were intact, but permeable to DAPI and PI (nonviable). This work demonstrates the importance of controlling factors that may impact the viability of oocysts when conducting studies that examine the transport of these microorganisms in the environment and through water treatment processes.

Animals↗

PubMed1985

Brain specific gravity and CT scan density measurements after human head injury.

White matter specific gravity was measured using the microgravimetric method in 20 comatose patients with diffuse head injury who were undergoing intracranial pressure (ICP) monitoring, and in 19 patients with focal injuries who were undergoing evacuation of contusions or intracerebral hematomas. Computerized tomography (CT) density readings were obtained for each site of white matter sampling by locating the sampling site on the preoperative CT scan. A significant correlation was found between the specific gravity values and the CT density numbers (r = 0.775; p less than 0.001). Patients with focal injuries demonstrated reduced perifocal specific gravity, suggesting brain edema. The mean specific gravity in patients with diffuse injury was within the normal range. In 10 of 12 patients in whom the specific gravity was above the normal range, the CT density was also above the normal range. These data suggest that cerebral vascular engorgement is the cause of the high specific gravity. Six (60%) of this small subgroup of 10 patients also demonstrated a high ICP.

Adult↗

PubMed1998

First-morning urine specific gravity and enuresis in preschool children.

The object of the study was to determine whether a first-morning urine specific gravity of less than or equal to 1.015 was associated with enuresis in children 3 to 6 years old. Parents of preschool children seen at the Cleveland Clinic Foundation during a 5-month period completed a questionnaire concerning bed-wetting and voiding habits of their child and collected first-morning urine specimens for specific gravity analysis. Of 101 children, 12 had a urine specific gravity of less than or equal to 1.015 (11.9%), including seven of 73 (9.6%) nonbed-wetters, two of 19 (10.5%) bed-wetters by history (who did not wet their beds on the night of the study), and three of nine (33.3%) bed-wetters (who wet their beds on the night of the study). The 73 nonbed-wetters (72.3%) had a mean (+/- standard deviation) urine specific gravity of 1.022 (+/- 0.006); 19 bed-wetters by history (18.9%) had a mean urine specific gravity of 1.024 (+/- 0.006); and nine bed-wetters (8.9%) had a mean urine specific gravity of 1.019 (+/- 0.005). The groups' mean urine specific gravities were not significantly different (p = 0.10) and the enuretic children were not more likely to have first-morning-void urine specific gravity of less than or equal to 1.015 than nonenuretic children (p = 0.14). Enuretic children who wet their beds on the night of the study had lower mean urine specific gravity than nonbed-wetters although the difference was not significant. Therefore, we do not recommend routine use of first warning void urine specific gravity analysis for predicting presence or absence of enuresis.

Age Factors↗

PubMed1987

Quantitative measurements of retinal edema by specific gravity determinations.

We have quantified retinal edema in rat by specific gravity measurements in vitro. Specific gravity corresponds to tissue water content, which is increased in retinal edema. The gravimetric analysis of retinal edema corresponds well with light and transmission electron microscopy and radiolabelled albumen studies. Specific gravity measurements are the standard method to measure brain edema and are also applicable to the measurement of retinal edema.

Animals↗

PubMed1982

Determination of the specific gravity of certain helminth eggs using sucrose density gradient centrifugation.

The specific gravities of ten species of helminth eggs were determined using sucrose density gradient centrifugation. Fecal or egg concentrate was layered over a 3 to 54% sucrose density gradient. The gradient was then centrifuged at 800 g for 20 min, allowing 5 min for acceleration and 5 for deceleration. Bands formed were identified and measured. Refractive index was measured at the middle of narrow bands, or at the level at which the concentration of eggs was highest, in the case of wide bands or when no band was formed. The specific gravity corresponding to this refractive index was taken as the specific gravity of the eggs. The ten species of helminth eggs studied and specific gravities measured on three or four gradients were: Toxascaris leonina, 1.0559; Ancylostoma caninum, 1.0559; Toxocara canis, 1.0900; Parascaris equorum, 1.0969; Toxocara cati (embryonated), 1.1005; Ascaris suum, 1.1299; Trichuris suis, 1.1299; Trichuris vulpis, 1.1453; Taenia sp., 1.2251; and Physaloptera sp., 1.2376. These determinations agree with or approximate those of previous workers. The specific gravities of P. equorum, T. suis, Taenia sp., and Physaloptera sp., are reported for the first time.

Animals↗

PubMed1994

Replacing creatinine measurements with specific gravity values to adjust urine cotinine concentrations.

Creatinine and specific gravity (relative density) measurements both allow differences in urine concentration to be taken into account in determining urine cotinine concentrations. In this study we demonstrate that the variance of urine cotinine measurements is reduced comparably when either creatinine or specific gravity measurements are used for correction. This reduction in variability improves the correlation between urine cotinine measurements and clinical endpoints. In this study, the clinical endpoints were pulmonary function in a population of nonsmoking children with asthma, 42% of whom were reported to have been exposed to environmental tobacco smoke. When corrected by either creatinine measurements or specific gravity values, the urine cotinine measurements performed as well or better than reported exposure (and comparably with each other) in assessments of lung function. A dose-response relationship was also more consistently apparent. Specific gravity values can be used reliably in place of creatinine values to adjust urine cotinine measurements for both research and clinical purposes.

Asthma↗

PubMed1991

Effect of source and amount of fiber on kinetics of digestion and specific gravity of forage particles in the rumen.

This experiment investigated the relationship between kinetics of digestion and change in specific gravity during in situ incubation. Nine cows were fed three sources of fiber (corn silage, alfalfa silage, or alfalfa hay) in diets formulated to contain 25, 30, or 35% NDF in three simultaneous 3 x 3 Latin squares. Method of alfalfa preservation did not influence rate of digestion or rate of increase in specific gravity of forage particles measured by a flotation technique. Prior to incubation, specific gravity of forage particles was in increasing order: alfalfa hay, alfalfa silage, and then corn silage. Essentially, all particles with a specific gravity less than 1.0 shifted to a higher specific gravity fraction by hydration within the first 4 h of incubation. From 4 to 56 h of incubation, percentage of residual DM that settled in solution having specific gravity of 1.3 increased linearly from 21 to 27% for corn silage but exponentially from 3 to 20% for alfalfa forages. Fractional rates of DM and NDF digestion and increase in percentage of residual DM having a specific gravity greater than 1.3 increased with the amount of fiber in the alfalfa diets and were correlated positively, suggesting that rate of increase in specific gravity, which affects rate of passage from the rumen, is influenced by rate of digestion of forage particles.

Animal Feed↗

PubMed1998

Specific gravity of Opisthorchis viverrini eggs.

The specific gravity of the eggs of the liver fluke Opisthorchisviverrini was determined using a sucrose gradient centrifugation and found to range from 1.2713 to 1.3043. The peak egg count was located at the sucrose fraction with a specific gravity of 1.2814. An attempt to float eggs in saturated sodium nitrate solution, sp.gr. 1.4, failed. Examination of human stool specimens for Oviverrini eggs by simple flotation in saturated sodium nitrate solution and the formol-ether sedimentation technique revealed that the flotation technique was not as efficient as the sedimentation technique. It was suggested that the flotation techniques were inappropriate for the detection of Oviverrini eggs in faeces or contaminated soil.

Animals↗