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PubMed1978

Performance evaluation of multi-channel analyzers by use of linearly-related survey specimens.

Sets of specimens having quantitative linear inter-relationships for 25 analytes were prepared and used in a small survey of results with multi-channel analyzers. Instrument calibration was evaluated by linear regression analysis of the analytical results, with calculation of the x- and y-intercepts and slopes. The average intercepts and slopes agreed quite well with those expected on the basis of specimen preparation, but the results from individual laboratories and from particular kinds of instruments demonstrated a variety of analytical biases. We conclude that performance of multi-channel analyzers can be evaluated effectively by such use of linearly related specimens in an inter-laboratory survey.

Autoanalysis↗
PubMed1983

Effect of continuous positive airway pressure on the ventilatory response to CO2 in preterm infants.

The effect of continuous positive airway pressure (CPAP) on the ventilatory response to CO2 in newborn infants is unknown. The CO2 response to 4% CO2 in air was studied in nine preterm infants without lung disease before and during administration of CPAP (4 to 5 cm H2O) delivered by face mask. Minute ventilation, tidal volume, respiratory frequency, and end-tidal PCO2 were measured, and the slope and intercept of the CO2 response were calculated. Respiratory pattern and changes in oxygenation were also analyzed by measuring inspiratory and expiratory time, mean inspiratory flow, mean expiratory flow, effective respiratory timing, end-tidal PO2, and transcutaneous PO2. CPAP significantly decreased minute ventilation from 278.7 to 197.6 mL/min/kg (P less than .001). Tidal volume and respiratory frequency were also significantly decreased. The slope of the CO2 response during CPAP was not significantly different from the slope before CPAP (36 v 33 mL/min/kg/mm Hg, P greater than .1), but the intercept was shifted to the right (P less than .001). The decrease in respiratory frequency was primarily due to a prolongation of expiratory time (P less than .05). In addition, transcutaneous PO2 increased during administration of CPAP (P less than .001). These findings indicate that: (1) CPAP significantly decreases ventilation in preterm infants without lung disease, affecting both tidal volume and respiratory frequency; (2) CPAP does not appreciably alter the ventilatory response to CO2; (3) the changes in respiratory frequency are primarily accounted for by a prolongation of expiratory time; (4) CPAP improves oxygenation.

Carbon Dioxide↗
PubMed1984

Effects of bronchodilation on magnitude estimation of added resistive loads in asthmatic subjects.

The magnitude estimation of 6 added resistive loads (delta R), ranging from 2.7 to 22.5 cmH2O/L/s, was studied in 7 normal and 6 stable asthmatic subjects. Each subject squeezed a handgrip dynamometer to indicate load magnitude. The magnitude estimation of a range of 5 weights, from 0.1 to 1.0 kg, placed on the hand was also assessed by dynamometry and numerical estimation. Airways resistance and spirometry were measured in each group. Metaproterenol, 0.13 mg, was then given by inhalation; after 15 min, the complete study was repeated. There was a significant bronchodilation in the asthmatic subjects, with a subjective decrease in chest "tightness," but no significant change in the normal subjects. In the control state, the perceived magnitude (psi) of delta R could be expressed by the relationship: psi = K. delta R beta, in accordance with Stevens' law. There was no significant difference (p greater than 0.05) in the value of beta between the normal and asthmatic group (0.55 and 0.67, respectively). However, the y-intercept in the control state was significantly greater in the asthmatics; when the perceived magnitude was expressed in terms of the mouth pressure (Pm) during the loaded breath in the control state, i.e., psi = K.Pm beta, there was no significant difference, either in beta or in the y-intercept. These results suggest that psi is related to Pm and is greater for any delta R in asthmatics because Pm is increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1984

The Ektachem clinical chemistry slide for simultaneous determination of unconjugated and sugar-conjugated bilirubin.

Using dual-wavelength spectrometry, we have refined the mordant-based bilirubin slide method (Clin Chem 28:2366-2372, 1982) to co-detect unconjugated bilirubin (Bu) and its sugar conjugates (Bc) in 10 microL of serum. The assay is based on three principles: (a) mono- and diconjugated bilirubins behave spectrally like one fraction (Bc) when bound to the mordant, (b) Bu and Bc are spectrally distinct, and (c) B delta (the bilirubin-albumin complex) is not measured in the film. With known bilirubin mixtures, results by the assay agree with those by nuclear magnetic resonance, by a Jendrassik-Gróf method for total bilirubin, and by a liquid-chromatographic procedure. With patients' sera, the slide correlates with a liquid-chromatography-augmented Jendrassik-Gróf method, according to the following typical regression statistics (in mumol/L): for Bu, slope = 0.992, r = 0.996, intercept = -0.376, Sy X x = 5.08; for Bc, slope = 0.970, r = 0.985, intercept = -0.735, Sy X x = 8.16. The method is precise (for Bu, CV = 5.2% at an average concentration of 16.4 mumol/L, and 4.1% at 66.7 mumol/L; for Bc, CV = 6.5% at 23.4 mumol/L, and 3.8% at 151.7 mumol/L for pools of patients' sera), is relatively interference free, and has potential for extension to further applications.

Adult↗
PubMed1981

Enzyme immunoassay for thyroxine and triiodothyronine in human serum, with use of a covalent chromatographic separation method.

A practicable enzyme immunoassay for measurement of thyroxine and triiodothyronine in serum was developed, involving a separation method based on the thiol-disulfide interchange reaction. Serum samples at alkaline pH were incubated for 1 h with antibodies and antigens labeled with beta-D-galactosidase. Each reaction mixture was then passed through a 0.1-mL column containing (anti-IgG) antibody immobilized on Sepharose 4B, to which the anti-IgG antibodies were coupled by means of a disulfide bond (3 g of IgG fraction per liter). The column was washed and the bound form of the label then was eluted from the column with a buffer containing dithiothreitol (25 mmol/L) by splitting the disulfide bonds between the anti-IgG antibody molecules and Sepharose matrix. From the enzyme activity in the eluate, concentrations of thyroxine or triiodothyronine in serum could be determined. Values obtained by this method and those obtained by a radioimmunoassay correlated well (thyroxine, r = 0.97, slope = 1.1 y-intercept = -0.94 microgram/L, n = 70; triiodothyronine, r = 0.98, slope = 0.91, y-intercept = 0.067 microgram/L, n = 77.

Chemical Phenomena↗
PubMed1982

Nature of the inhibition of Cl- transport by furosemide: evidence for competitive inhibition of active transport in toad cornea.

Furosemide inhibits short-circuit current (active Cl- transport) in isolated toad cornea, a model of the thick ascending limb of the loop of Henle. The relationship between furosemide and Cl- was assessed in corneas exposed to different concentrations of Cl-. Furosemide (2.2 x 10(-5) M) or drug vehicle was added to both sides of the corneas. Double-reciprocal plots of short-circuit current vs. Cl- concentration with or without furosemide revealed an interaction between furosemide and Cl- that appeared to be competitive in nature. That is, the 1/short-circuit current x 10(3) intercepts (short-circuit currentmax) of the lines were not significantly different (54 with furosemide and 40 for the control, P = .765), whereas the slopes of the lines were significantly different (7.9 with furosemide and 2.1 for the control, P = .037). Km values calculated from the slopes and intercepts with and without furosemide were 145 and 53 mM, respectively. The relationship between external Cl- and furosemide was unique in that a similar competitive relationship was not apparent for either external Na+ and furosemide or external Cl- and ouabain (another inhibitor of Cl- transport in amphibian cornea). These findings support the hypothesis that furosemide inhibits active Cl- transport by competitively blocking the access of Cl- to some component of the active transport mechanism, possibly the Na+-Cl- cotransport mechanism.

Animals↗
PubMed1983

An enzymic creatinine assay and a direct ammonia assay in coated thin films.

We developed a thin-film enzymic assay for creatinine that makes use of creatinine iminohydrolase (EC 3.5.4.21) to convert creatinine to N-methylhydantoin and ammonia. The ammonia diffuses through a semipermeable layer and is quantitated by reaction with bromphenol blue. A paired analysis of the sample on a separate coating without the enzymic reaction measures endogenous ammonia and, for samples with normal concentrations of ammonia, allows accurate determination of serum creatinine to 150 mg/L without dilution. Results of this assay (y) compare well with those by a liquid-chromatographic comparison assay (x) by linear regression (slope = 0.935, intercept = 1.13 mg/L, r2 = 0.995). It is insensitive to many substances, such as ketones and keto acids, that interfere with conventional assays. Results of the ammonia assay (y) correlate well with those by a semi-automated enzymic assay (x) based on glutamate dehydrogenase (slope = 1.068, intercept = 17.3 mumol/L, r2 = 0.985).

Ammonia↗
PubMed1978

Comments on the use of the additive factor method with mentally retarded persons: a reply to Silverman.

Maisto and Jerome (1977) reported a choice reaction time (RT) study relating the rate of memory scan to level of intellectual functioning. In this study, slope and intercept values of the RT function were found to be inversely related. Silverman (1978) has raised some concern over the conclusions reached by Maisto and Jerome due to the slope-intercept relationship revealed in their study, which seemingly violates one of the underlying assumptions of the additive factor method. Data were presented from previously reported research that places a number of studies with retarded persons as subjects suspect to this violation. Possible explanations for this finding were also provided.

Adolescent↗
PubMed1982

Four methods for determining uric acid compared with a candidate reference method.

Uric acid as measured in serum by three different uricase (EC 1.7.3.3) methods (aca, Ektachem, and SMAC) and by the SMAC method with phosphotungstic acid was compared with a candidate Reference Method for uric acid. Serum specimens from 83 patients (uric acid concentrations, 19 to 141 mg/L) were analyzed by all five methods. Results were compared by using linear regression analysis, and the mean difference between results by the candidate Reference Method and the four other methods was calculated. Compared with the candidate Reference Method, the aca method gave the smallest deviation from zero for the intercept and the smallest mean difference, and the SMAC phosphotungstic acid method showed a slope closest to unity. The SMAC uricase method had the largest intercept and greatest deviation of the slope from unity.

Autoanalysis↗
PubMed1980

Studies of limb-dislodging forces acting on an ejection seat occupant.

A mathematical theory is being developed in order to calculate the aerodynamic loading to which a pilot is exposed during high-speed ejections. Neglecting the initial effects of flow separation, results thus far indicate that a pilot's musculoskeletal system is not likely to withstand the tendency for limb-flailing if he is ejecting at Mach numbers in excess of about 0.7. This tendency depends very strongly upon the angle at which the pilot's limbs intercept a high-speed flow; the forces that cause limb dislodgement increase dramatically with speed of ejection. Examining the time-course of limb-dislodging forces after the initial onset of windblast, the theory further predicts the generation of a double vortex street pattern on the downstream side of the limbs of an ejection seat occupant. This results in the corresponding appearance of oscillating forces tending to cause lateral motion (vibration) of the limbs. The amplitude and frequency of these oscillating forces are also very dependent on the Mach number of ejection and the angle at which the pilot's limbs intercept the flow. However, even at moderate Mach numbers, the frequency can be as high as 100 cycles per second, and the amplitude rapidly exceeds a pilot's musculo-skeletal resistive powers for Mach numbers above 0.7.

Aerospace Medicine↗
PubMed1981

Improved method for determination of high-density-lipoprotein cholesterol I. Isolation of high-density lipoproteins by use of polyethylene glycol 6000.

We describe a modified method of precipitating low- and very-low-density lipoproteins with polyethylene glycol, for quantitation of high-density lipoprotein cholesterol. A 100 g/L concentration of polyethylene glycol 6000 in a buffered (pH 10) solution is used. Under these conditions precipitation of beta-lipoproteins is complete. Values for HDL cholesterol as measured with this method fully correspond to those obtained on separating the lipoproteins by ultracentrifugation or with heparin-Mn2+, 46 mmol/L; are slightly higher than those obtained with heparin-Mn2+, 92 mmol/L; and are significantly higher than those determined after precipitation with polyethylene glycol, 100 g/L at pH 8.0. Comparison with results by the ultracentrifugation method showed excellent correlation (r = 0.957) with a good correspondence of results (slope 1.065 and y-intercept -22.231); comparison with the heparin-Mn2+, 46 mmol/L, method gave r = 0.998 with slope of 0.985 and y-intercept 2.963. The method is unaffected by precipitation and centrifugation time and temperature (up to 24 h with 4-22 degrees C temperature for precipitation and between 10 and 30 min with 4-22 degrees C temperature for centrifugation). This extremely simple method is particularly suitable for routine analyses of many samples, even in small laboratories.

Chemical Precipitation↗
PubMed1995

[Hypodontia: considerations on orthodontic therapy in agenesis of the permanent upper lateral incisor].

The authors have investigated different clinical cases having in common the agenesis of the permanent upper lateral incisors, to evaluate from a clinical and esthetic point of view the possibilities, results and the limits of the orthodontic treatment. These are nowadays increasingly associated with esthetic dentistry, prosthodontics, implantology and finally with dental transplantation. The patients presented the absence of one or both permanent upper lateral incisors or the agenesis of other teeth, sometimes associated with dental crowding or a not favourable intermaxillary relation. Most of the cases were treated with compensatory extraction of the other normal or hypoplastic permanent upper lateral incisor. The results were satisfactory but the mean treatment time was relatively long (56 months, including the retention phase), according to the difficulty of obtaining a good esthetic result in the smile line. The importance of a correct point of time of the interception for the choice of the most adequate therapy is emphasized. The possibility of correcting occlusal relation by means of the orthopedic treatment of the maxillary structures is limited to the end of the deciduous dentition. The diagnostic criteria for a correct and opportune interception of this anomaly are being stressed on. Finally the esthetic problems arising of the orthodontic space closure and the possible solutions were discussed.

Adolescent↗
PubMed1995

Laboratory evaluation of the Miles H.3 automated reticulocyte counter. A comparative study with manual reference method and Sysmex R-1000.

OBJECTIVE: To evaluate the performance of the new commercial Miles H.3 RTX analyzer in counting reticulocytes. METHODS AND PATIENTS: The results from the counter were compared to those obtained from microscopic methods, following the National Committee for Clinical Laboratory Standards H44-P guidelines, and to the results from the Sysmex R-1000 counter. In total, 279 samples were analyzed in duplicate with each of the three methods. One hundred thirty-three samples were from healthy subjects, while 146 were from patients with various pathologies, 10 of whom presented with posttherapeutic aplasia of the bone marrow and 9 with iron-deficiency anemia. RESULTS: The reference intervals for the normal controls are different for each of the three methods (manual: 0.35-2.35%, 16 to 116 x 10(9)/L; Miles H.3: 0.65-2.30%, 35.1 to 112.0 x 10(9)/L; Sysmex R-1000: 0.6-1.85%, 28.0 to 85.0 x 10(9)/L). The overall imprecision was lower for the instruments than for the microscopic method (Miles H.3: coefficient of variation, 11.6%; R-1000: coefficient of variation, 4.2%; microscopic method: coefficient of variation, 24.2%). The Miles H.3 shows a good correlation with the other methods, yet it overestimated the low values with respect to both the microscopic method (intercept, 0.55; slope, 0.70) and the R-1000 (intercept, 0.44; slope, 0.78). This became particularly pronounced in patients with marrow aplasia. CONCLUSIONS: Miles H.3 can produce results with an acceptable degree of accuracy. The agreement with the dedicated fluorescence-based flow cytometer R-1000 at normal and high concentrations is also good. The possibility of providing reticulocyte indices as well as erythrocyte indices (mean volume, mean hemoglobin content, mean hemoglobin concentration) and the relative dispersion indices could be useful in understanding red cell pathophysiology in normal and iron deficient patients.

Anemia, Aplastic↗
PubMed1995

Fluorescent vs. radioactive microsphere measurement of regional myocardial blood flow.

OBJECTIVES: This study compared simultaneous regional myocardial blood flow (RMBF) measurements using fluorescent microspheres (FM) and radiolabeled microspheres (RM). The utility of an internal standard during processing was also examined. METHODS: Paired FM and RM were injected into the left atrium of 9 anaesthetised rabbits. RMBF was altered by use of either regional ischaemia or (-)-N6-(2-phenylisopropyl)-adenosine. Radioactivity of blood reference and tissue samples was quantitated using standard methods. Samples were then digested with potassium hydroxide and microspheres recovered by vacuum filtration, with an additional label of FM as the internal standard. FM labels were extracted using Carbitol acetate and quantitated using fluorescence spectroscopy. Agreement between the fluorescent and radioactive methods was assessed using both orthogonal regression and difference-against-mean analyses. RESULTS: Using recovery-uncorrected data, the slope of the orthogonal regression of RM and FM-determined RMBF was not statistically different from 1, but the intercept was statistically different from 0 [-0.03(0.01), P = 0.005] and the mean RMBF by each method differed from one another [1.24(0.08) vs. 1.17(0.08) ml.min-1.g-1, P = 0.0002]. The mean +/- 2 s.d. of the differences of RMBF (RM minus FM) was +0.07 +/- 0.30 ml.min-1.g-1. Although recovery of FM from tissue averaged 97.6(1.2)%, use of the internal standard to correct for losses substantially improved the agreement between RM and FM-determined RMBF: the orthogonal regression slope was not statistically different from 1, the intercept was not statistically different from 0, and the means of the flows were not different. The mean +/- 2 s.d. of the differences of RMBF was -0.01 +/- 0.22 ml.min-1.g-1. The internal standard also improved RMBF estimates from samples with simulated large spillage during processing. CONCLUSION: Fluorescent microspheres are an equivalent alternative to radiolabeled microspheres for the estimation of RMBF. Although the overall recovery of microspheres using this technique was high, use of an internal standard is recommended for correction of random losses.

Animals↗
PubMed1979

Relative potencies and durations of action with respect to respiratory depression of intravenous meperidine, fentanyl and alphaprodine in man.

Fentanyl, 0.7 and 1.4 microgram/kg, alphaprodine, 0.135 and 0.270 mg/kg meperidine, 0.564 and 1.127 mg/kg, and placebo were administered intravenously over 2.6 min by infusion to five healthy adult males. The crossover study was of incomplete Latin square design with at least 1 week between administrations of each study drug. The subjects breathed from a mixing chamber the gas composition of which was servo-controlled so as to produce CO2 ramps in the end-tidal gases. Each experiment was composed of: 1) control CO2 ramps, 2) a 25-min isocarbic run during which the drug was infused and 3) CO2 ramps at half-hour intervals for 3 hr postinfusion. The 20-liter intercept (the PETCO2 at which ventilation was 20 liters/min) was used as the measure of respiratory drive; the change in 20-liter intercept measured drug effect. The potency ratios at peak effect were: fentanyl/meperidine, 679; alphaprodine/meperidine, 3.68; fentanyl/alphaprodine, 179. With the area under the time-effect curves, the potency ratios of mean effect were: fentanyl/meperidine, 45c; alphaprodine/meperidine, 3.00; fentanyl/alphaprodine, 141. Thus, both fentanyl and alphaprodine are shorter-acting than meperidine, and fentanyl is shorter-acting than alphaprodine. The time-effect curves were fitted to linear and mono- and bi-exponential models. The time constants were compatible with the above relative durations of action.

Adult↗
PubMed1995

epsilon-Aminocaproic acid does not inhibit outflow resistance washout in monkeys.

PURPOSE: To determine whether the anti-fibrinolytic agent epsilon-aminocaproic acid (EACA) inhibits the washout of resistance to aqueous humor outflow during anterior chamber perfusion in cynomolgus monkeys, as it does in rabbits. METHODS: Nine adult ocular normotensive cynomolgus monkeys underwent bilateral anterior chamber perfusion with Bárány solution, containing 3.8 mM EACA unilaterally. Total outflow facility was determined in both eyes simultaneously for approximately 4 hours by the two-level constant pressure method. The data were analyzed using a linear regression model that tested treated versus control eye differences over time against a slope and intercept of 0.0. RESULTS: Outflow facility increased and resistance decreased significantly over time similarly in both EACA-treated and control eyes; i.e., neither the slopes nor the intercepts for facility or resistance, respectively, differed between the eyes over the entire 4-hour measurement period or for the initial 90 minutes considered separately. The facility increase and resistance decrease as functions of perfusion volume also were similar in EACA-treated and control eyes. CONCLUSIONS: EACA at this dose does not prevent resistance washout in the cynomolgus monkey, in contrast to the rabbit. This species difference may relate to the vastly different anatomy and physiology of their outflow pathways.

Aminocaproic Acid↗
PubMed1995

Inference for the association between coefficients in a multivariate growth curve model.

This paper generalizes the work of Blomqvist (1977, Journal of the American Statistical Association 72, 746-749) on inference for the relationship between the individual-specific slope and the individual-specific intercept in a linear growth curve model. The paper deals with longitudinal data involving one or more response variables and irregular follow-up times, with each response variable postulated to follow a linear growth curve model. The problem considered is inference concerning the association between one growth curve coefficient and another--for example, the slope and intercept for a selected response variable, or the two slopes for two different response variables--after adjusting for all remaining coefficients among all of the response variables. An inferential approach based on the method of moments and an inferential approach based on maximum likelihood are described, and the asymptotic properties of these procedures are presented. Extensions of the methodology to allow polynomial growth curves and baseline covariates are outlined. The methodology is illustrated with a practical example arising from a clinical trial in lung disease.

Body Height↗
PubMed1995

%VO2max versus %HRmax regressions for six modes of exercise.

The purpose of the study was to compare the %VO2max versus %HRmax regression equations developed from data collected during incremental work on six exercise modes: treadmill (T), cycle (C), skier (S), shuffle skier (SS), stepper (ST), and rower (R). Ten active males were habituated to all modes and then performed an incremental test to maximum on each mode. Mode order was assigned by Latin square sequences and the tests were separated by at least 72 h. VO2 and HR were recorded at each increment. Regression analyses were performed using SAS-GLM. Regressions for T, S, SS, and ST were not significantly different. C had a lower intercept and higher slope, while R had a higher intercept and lower slope than the other exercise modes. These results suggest that weight bearing exercise modes have similar %VO2max-%HRmax regressions. However, weight supported and arm exercise modes appear to have different regressions.

Adult↗