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J Toffaletti

Publications and source records attributed to J Toffaletti.

At least 37 records · Page 2Linked to original sources
PubMed1985

Influence of continuous infusion of citrate on responses of immunoreactive parathyroid hormone, calcium and magnesium components, and other electrolytes in normal adults during plateletapheresis.

To study the relationships between changes in concentrations of different forms of calcium and the responses of immunoreactive PTH in humans during citrate-induced hypocalcemia, we studied 12 healthy donors undergoing continuous flow plateletapheresis. Concentrations of intact, amino-terminal, and midregion PTH; ionized, ultrafiltrable, and total calcium; total and ultrafiltrable magnesium; protein; albumin; pH; phosphate; and citrate were measured in sera collected during the first 95 min of apheresis. Although ionized calcium decreased steadily in every donor, both intact and amino-terminal PTH rose quickly in most donors to a peak level 5-15 min after starting the infusion of citrate and then declined during the remainder of apheresis. Midregion PTH also rose quickly by 5-remainder of apheresis. Midregion PTH also rose quickly by 5-15 min, but levelled off at 30-90 min. Total calcium inversely correlated with both intact PTH (r = -0.76) and amino-terminal PTH (r = -0.81) better than did ionized calcium (r = -0.47 and -0.46, respectively). The rapid rise and then gradual fall of PTH may be due to glandular depletion of stored PTH, increased peripheral metabolism of PTH, or PTH initiation of other hormonal actions that compensate for hypocalcemia. Protein-bound calcium measured, and this change probably reflected dissociation of calcium from its albumin-binding sites to minimize the changes in ionized calcium concentrations.

Adult↗
PubMed1985

Preparation and use of serum-based material as control and calibrator in evaluating ion-selective electrodes for calcium.

We analyzed 93 sera and 81 whole-blood samples, plus several aqueous materials and one serum-based material as controls, with two analyzers for ionized calcium (Radiometer ICA 1 and AVL 980). On 16 days, comparisons of results for patients' samples were good, with nearly all between-instrument differences (delta Ca2+) of samples being within 0.04 mmol/L. On 12 days, comparisons were mediocre, with the delta Ca2+ of samples usually 0.04 to 0.10 mmol/L. The control material that most consistently indicated the direction and magnitude of the delta Ca2+ of patients' samples was the serum-based control. Adjustment of results for samples from patients, based on the delta Ca2+ of the serum control on the same day, substantially improved comparisons between instruments. Our findings suggest that the use of a serum-based calibrator provides the most valid comparison between different calcium-ion analyzers and reliably indicates when electrode replacement is needed.

Autoanalysis↗
PubMed1984

Effects of storage temperature and time before centrifugation on ionized calcium in blood collected in plain vacutainer tubes and silicone-separator (SST) tubes.

We studied the stability of ionized calcium and pH in samples stored at either room temperature or 4 degrees C, in centrifuged and uncentrifuged blood-collection tubes and in centrifuged tubes containing a silicone-separator gel (SST tubes). At room temperature, in uncentrifuged blood from healthy individuals, mean ionized calcium usually increased no more than 10 mumol/L per hour; at 4 degrees C it did not change detectably for 70 h. This stability was fortuitous, however: the concentrations of both hydrogen and lactate ions in these samples increased, apparently with offsetting effects on the concentration of ionized calcium. Blood stored for 70 h at 4 degrees C in centrifuged SST tubes, although showing a slightly greater change in ionized calcium, had less change of pH and no change in the ionized calcium corrected to pH 7.4. In 11 heparinized whole-blood samples from eight patients in intensive care, the mean change per hour in ionized calcium and pH after storage at room temperature was +10 mumol/L and -0.04 units, respectively.

Acute Disease↗
PubMed1983

Total, ultrafiltrable, dialysable and ionised calcium measurements in randomly selected samples compared with clinical diagnoses.

Total, ultrafiltrable (Worthington 'Ultrafree'), dialysable and ionised (Orion SS-20) calcium levels were measured in 110 serum samples selected randomly from patients for whom total calcium was ordered as a routine test. The available medical records were used to categorize most of the 86 patients as a guide to determining if the calcium results were appropriate to the diagnosis. Total calcium measurement was precise and reliable but was affected by the albumin level. Dialysable calcium measurement was good for diagnostic purposes and was not affected by albumin. Of 25 patients with apparently normal calcium metabolism, six had elevated ultrafiltrable calcium results. Ionised calcium measurement required the most time and sample and offered few, if any, clear advantages in diagnosis over the other free calcium tests. Further improvements in ionised calcium measurements appear to be needed.

Calcium↗
PubMed1983

An automated dry-slide enzymatic method evaluated for measurement of creatinine in serum.

We evaluated an automated dry-slide enzymatic method involving creatinine iminohydrolase for measurement of creatinine in serum with the Kodak Ektachem analyzer. The means (and SD) for three commercially available quality-control sera, analyzed during eight weeks, were 9.7 (1.0), 16.6 (0.9), and 61 (2.1) mg/L. The regression equation for 105 samples measured with the Technicon SMAC (x) and Ektachem Analyzers (y) was: y = (0.89 +/- 0.007)x + (1.7 +/- 0.3) mg/L and for 170 samples measured with the Beckman Astra (x) and Ektachem analyzers (y): y = (1.00 +/- 0.005)x - (1.9 +/- 0.16) mg/L. Sixty-one samples from renal-transplant patients showed nearly the same agreement. The enzymatic method had no interference from substances that interfere with many Jaffé methods for creatinine, including acetoacetate. The drugs cephalothin and cephoxitin did not interfere, but 5-fluorocytosine interfered significantly with creatinine in the Ektachem method. Values for several ketone-positive sera were 5 to 10 mg/L higher by the Astra relative to the Ektachem. Grossly hemolyzed or lipemic samples were analyzed without difficulty. We conclude that this enzymatic method for creatinine in serum has the speed and precision necessary for routine clinical laboratory use and, except for one drug, the method appears to be specific for creatinine.

Aminohydrolases↗
PubMed1982

Enzymic determination of citrate in serum and urine, with use of the Worthington "ultrafree" device.

We describe an enzymic method for conveniently measuring citrate in serum or urine. Interfering enzyme proteins are removed by a disposable ultrafilter ("Ultrafree"; Worthington Diagnostics), obviating the need for hazardous protein precipitants. A 50 mmol/L Tris buffer adequately controls pH, no lactate dehydrogenase is necessary in the reagents, and the reaction of citrate catalyzed by citrate lyase (EC 4.1.3.6) is complete in 2-3 min. Within-run and day-to-day coefficients of variation were 7.5% and 5.4%, respectively. Serum citrate concentrations for 20 apparently healthy persons ranged from 0.08 to 0.17 mmol/L (mean 0.12, SD 0.03). Urinary citrate excretion by six normal volunteers ranged from 2.2 to 4.4 mmol/24 h. We observed no detectable changes in citrate in whole blood stored at room temperature for 90 min or longer. Overall, the method is faster and less hazardous than other methods for citrate that require protein precipitation.

Citrates↗
PubMed1981

The Worthington "ultrafree" device evaluated for determination of ultrafiltrable calcium in serum.

We evaluated a commercially-available disposable device ("Ultrafree," Worthington Diagnostics) for the anaerobic preparation of protein-free ultrafiltrates from serum for measurement of ultrafiltrable calcium. Sufficient filtrate for the analysis is obtained with 10 min from 0.2 to 0.4 mL of serum at room temperature. We assessed these ultrafilters with regard to permeability of calcium citrate, exclusion of proteins, frequency of leakage, and effect of temperature on results. Within-run and day-to-day coefficients of variation for human serum pools were 1.2 and 1.5%, respectively. Reference intervals (in mmol/L) for total (2.16-2.58), ultrafiltrable (1.44-1.67), dialyzable (1.25-1.41), and ionized (1.04-1.25) calcium have been determined for a healthy population of 69 women and 81 men, ages to 18 to 65 years. The device appears to be the most practicable yet available for use in making this measurement.

Adolescent↗
PubMed1980

Spectrophotometric micro method for measurement of dialyzable calcium by use of cresolphthalein complexone and continuous-flow analysis.

We adapted a method for dialyzable calcium from fluorometric detection by use of calcein to a more specific spectrophotometric determination with cresolphthalein complexone. The reagents are available commercially and perform satisfactorily with respect to noise level, drift, stability, and sensitivity. Construction of the continuous-flow manifold with commercially available components (injection blocks, coils, and dialyzer) and the use of a 9-mm pathlength flow cell in an AutoAnalyzer I colorimeter have permitted a sampling rate of 70/h, and decreased the volume of serum required to 130 microL. A comparison of 71 sera analyzed by the present and the calcein method gave means of 1.39 (SD 0.14) and 1.39 (SD 0.13) mmol/L, respectively. The regression equation was: present method = 1.016 calcein--0.022 mmol/L (r = 0.97). The CV for the new method, as determined from 46 randomized duplicate analyses, was < 1%. The reference interval, as evaluated from results for 93 different individuals, was 1.26-1.43 mmol/L. We conclude that our methods is an improvement with respect to noise level, drift, specificity, detectability, and more general availability of instrumentation. Moreover, the smaller sample volume required makes possible the routine measurement of dialyzable calcium in pediatric samples.

Adult↗
PubMed1979

Improvements in and clinical utility of a continuous-flow method for routine measurement of dialyzable (ultrafiltrable) calcium.

We describe modifications to the original continuous-flow procedure for dialyzable calcium (Clin. Chem. 23: 1258, 1977) needed to make the method more suitable for routine clinical laboratory use. The modifications simplify the continuous-flow (AutoAnalyzer) manifold, decrease baseline noise, increase the sensitivity, and permit use of a less-expensive fluorometer. Bias due to variation in serum processing is minimized by use of serum samples minimally exposed to air and a pH 7.40 buffer in place of the routinely processed sera and pH 7.30 buffer used formerly. Day-to-day precision (CV) during the past year for samples that included three different lots of quality-control sera was 2 to 3%. The analysis requires 200 micro L of serum, collected with minor additional precautions. We find that dialyzable calcium can be dependably measured in the routine service laboratory and show how this information is clinically more useful than is information on total calcium in serum.

Autoanalysis↗
PubMed1979

Increase in dialyzable calcium associated with therapy with lithium.

We measured total and dialyzable calcium concentrations in consecutive sera submitted for routine lithium analysis. Of 98 samples from 61 different individuals, six (6.1%) total calcium results and 32 (33%) dialyzable calcium results were above the respective reference intervals. By comparison, when both total and dialyzable calcium were measured on 50 different apparently healthy volunteers, no results were outside either reference interval (2.20--2.58 mmol/L for total and 1.30--1.47 mmol/L for dialyzable calcium). These increases were not due to age or sex differences between the patients and controls. From the dialyzable calcium data, there appears to be an even higher incidence of mild hypercalcemia in patients receiving oral lithium salts than is indicated by the total calcium concentration alone.

Adult↗
PubMed1977

Continuous-flow determination of dialyzable calcium in serum.

We describe a procedure for measuring dialyzable calcium in 60 sera per hour with use of AutoAnalyzer (Technicon) modules. The serum is buffered, then dialyzed in a regular 6-inch (15-cm) dialysis block. A constant proportion of the dialyzable calcium is fluorometrically measured. Analysis of samples containing protein, prepared by an equilibrium dialysis technique, shows that protein-bound calcium is not detected. The method requires less than 0.4 ml of serum, and is accurate, precise, and durable. No unusual care or special techniques are required during sample collection or analysis.

Adult↗
PubMed1977

Use of gel filtration to examine the distribution of calcium among serum proteins.

Gel filtration of serum by use of dextran bisacrylamide beads ("Sephacryl S-200," fractionation range: 5000-250 000 daltons), separates the serum proteins into three distinct peaks. We used an eluent containing (per liter) 140 mmol of sodium, 1.10 mmol of calcium, 0.50 mmol of magnesium, and 10 mmol of 2-([2-hydroxy-1, 1-bis(hydroxymethyl)ethyl]amino)ethanesulfonate buffer (pH 7.43 at 37 degrees C) to provide the physiological conditions necessary to maintain the equilibrium of bound calcium in serum. We examined the calcium binding by each of the three protein groups. Calculating the calcium bound per gram of protein in each peak, we found that proteins in the first peak (alpha2-macroglobulin, IgM, haptoglobins) bind about the same amount of calcium per gram as does albumin. The proteins of the second peak (largely IgG and IgA) bind less calcium than does albumin, which is the protein accounting for 90% or more of the third peak. We also were able to calculate intrinsic association constants for calcium/albumin under physiological conditions.

Blood Proteins↗
PubMed1976

Separation and quantitation of serum constituents associated with calcium by gel filtration.

Gel filtration of serum by use of polyacrylamide beads (Biogel P-2) separates total colcium into four distinct peaks: an initial peak, corresponding to protein-bound calcium; a second peak containing the calcium complexes of citrate, phosphate, lactate, and sulfate; a third peak containing calcium bicarbonate; and a fourth peak or trough corresponding to the serum ionic calcium. An eluent containing (per liter) 140 mmol of sodium, 1.1o mmol of calcium, 0.50 mmol of magnesium, and 10 mmol of 2-([tris(hydroxymethyl)methyl]amino)ethanesulfonic acid(pH 7.40 at 37 degrees C) provides physiological conditions that determine the equilibria between these calcium components. Association constants determined under these conditions permit calculation of the expected concentration of the calcium complexes in each tube of eluent, and these concentrations closely correspond to the amount of bound calcium measured experimentally. The mean distribution of calcium in healthy individuals, as determined by this method, is (per liter): calcium protein, 1.00 mmol; calcium complexes, 0.31 mmol; and ionic calcium, 1.07 mmol.

Bicarbonates↗