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Results for “Absolute quantification”

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PubMed1989

Non-fibrous inorganic particles in human bronchoalveolar lavage fluids.

Bronchoalveolar lavage (BAL) is a simple and non-invasive sampling technique of the deep lung. Analytical electron microscopy was used for the identification and quantification of non-fibrous inorganic particles recovered in BAL fluid samples from 51 subjects with various occupational exposures (silica, silicates, metals and alloys, metallic oxides, precious and hard metals, abrasives). Around 4750 particles were analysed. More than sixty different compounds were identified, among which silica, kaolinite, illite, mica, Fe oxides and hydroxides, appeared to be ubiquitous. Feldspar, talc, chlorite, Al oxide, Ti oxide, tungsten carbide, stainless steel, carbonaceous compounds and flyash were also frequently encountered. From 1 to 21 compounds were identified in each sample. Repeated BAL samples obtained for 2 subjects did not show significant differences. Particles characteristic of the occupational exposure were found in BAL up to 21 years after cessation. BAL content can also reflect mixed occupational exposures. Absolute particle concentrations measured in twelve samples ranged between 0.1 and 9.9 x 10(6) particles/ml BAL fluid and mean particle diameter ranged between 0.5 and 1.2 microns. Mineralogical analysis of non-fibrous particles in BAL can be a useful tool to investigate occupational exposures. It allows, in most cases, a better characterization of the exposure than medical questioning. It may be helpful in identifying pathogenic particles, however it must be kept in mind that a positive result is only a proof of exposure and never a proof of disease. The main limitations of this technique are difficulties in sampling severely diseased subjects and inaccuracy in detecting easily soluble compounds and particles with a high rate of alveolar clearance.

Adult↗

PubMed2002

Quantification of the myocardial velocity gradient and myocardial wall thickening velocity in healthy children: a new indicator of regional myocardial wall motion.

Doppler tissue imaging allows the measurement of tissue motion velocity in real time. However, tissue velocities are affected by translational motion and by the angle of Doppler interrogation. The myocardial velocity gradient and myocardial wall thickening velocity, determined by color Doppler tissue imaging, can be used to evaluate regional wall thickening and thinning motion independent of translational motion. To determine the control values for myocardial velocity gradient and myocardial wall thickening velocity for the interventricular septum and posterior wall, we studied 120 healthy children (mean age: 7.8 +/- 5.0 years). Peak values of myocardial velocity gradient and myocardial wall thickening velocity at each cardiac phase were measured: systole, early diastole, and atrial contraction. The peak values of myocardial velocity gradient and myocardial wall thickening velocity were higher in the posterior wall than those in the interventricular septum, suggesting that thickening and thinning are more dynamic in the posterior wall. Linear regression analysis demonstrated that absolute values of myocardial velocity gradient at systole, early diastole, and atrial contraction, and wall thickening velocity at atrial contraction decreased with body surface area (BSA). On the other hand, absolute values of myocardial wall thickening velocity at systole and early diastole increased with BSA, and myocardial wall thickening velocity at early diastole in interventricular septum did not change. Myocardial velocity gradient at systole and early diastole, and myocardial wall thickening velocity at systole were strongly related to BSA. In contrast, myocardial velocity gradient and myocardial wall thickening velocity at atrial contraction strongly correlated with time interval between 2 consecutive QRS complexes. Because myocardial wall thickening velocity at early diastole in the interventricular septum did not correlate with BSA or time interval between 2 consecutive QRS complexes, it might evaluate diastolic function of interventricular septum independent of body size or heart rate.

Blood Flow Velocity↗

PubMed1999

Quantification of insensible water loss associated with insufflation of nonhumidified CO2 in patients undergoing laparoscopic surgery.

A growing number of surgical procedures of increased duration are being performed using laparoscopic techniques. No study to date has quantitated the potential insensible water loss associated with laparoscopic surgical procedures as a result of intra-abdominal humidification of insufflated nonhumidified CO2 gas. The purpose of this study was to quantitate this insensible water loss by measuring the CO2 gas volume consumed and the relative humidity of the vented gas. Ten patients presenting for elective procedures were enrolled in this descriptive prospective IRB-approved study. After secondary trocar placement and attainment of the desired intra-abdominal pressure, vented laparoscopic gas was passed directly through a dewpoint monitor sensor. Determinations of dewpoint and gas temperature were made immediately after the start of the surgical procedure and every 15 minutes thereafter until completion. Dew-point temperature was converted to relative humidity, which was used to determine the water vapor content of the gas. The actual water content (absolute humidity) of the vented laparoscopic gas was then calculated from the water vapor volume. The mean relative humidity of the vented laparoscopic gas was 92.2% +/- 0.8%. The mean laparoscopic gas flow rate was 42.0 +/- 5.0 L/h. The mean volume of water (absolute humidity) loss attributed to humidification of dry CO2 was found to be less than 1 mL/h. Insufflation of dry CO2 during laparoscopic procedures therefore results in insignificant insensible water loss.

Adult↗

PubMed1992

Detection of left anterior descending coronary artery disease in patients with left bundle branch block.

The detection of coronary artery disease is difficult if a patient has electrocardiographic evidence of left bundle branch block (BBB). Septal blood flow may be reduced in patients with left BBB, despite no angiographic evidence of left anterior descending (LAD) coronary artery disease. We have developed a new method of quantification of Thallium-201 single-photon emission computed tomographic (SPECT) images with the aim of better separating patients with left BBB and LAD disease from those with left BBB alone. The study cohort comprised 8 normal subjects (group I) and 20 patients with left BBB and chest pain who underwent thallium-201 SPECT imaging and coronary angiography. Eight patients (group II) had < or = 50% LAD stenosis, and 12 (group III) had > or = 70% LAD stenosis. Septal abnormality scores on the second short-axis slice from the base were computed, based on comparison of each subject's short-axis circumferential profile with a normal reference curve. This followed a procedure in which each profile was scaled to minimize differences in its absolute level in relation to the reference curve. Septal abnormality scores on stress images were 0.8 +/- 22 for group I, 27 +/- 43 for group II, and 165 +/- 67 for group III (p = 0.15 for group I vs II, and p < 0.0001 between groups I and III, and II and III).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed2000

Simultaneous quantification of acetanilide herbicides and their oxanilic and sulfonic acid metabolites in natural waters.

This paper describes a procedure for simultaneous enrichment, separation, and quantification of acetanilide herbicides and their major ionic oxanilic acid (OXA) and ethanesulfonic acid (ESA) metabolites in groundwater and surface water using Carbopack B as a solid-phase extraction (SPE) material. The analytes adsorbed on Carbopack B were eluted selectively from the solid phase in three fractions containing the parent compounds (PCs), their OXA metabolites, and their ESA metabolites, respectively. The complete separation of the three compound classes allowed the analysis of the neutral PCs (acetochlor, alachlor, and metolachlor) and their methylated OXA metabolites by gas chromatography/mass spectrometry. The ESA compounds were analyzed by high-performance liquid chromatography with UV detection. The use of Carbopack B resulted in good recoveries of the polar metabolites even from large sample volumes (1 L). Absolute recoveries from spiked surface and groundwater samples ranged between 76 and 100% for the PCs, between 41 and 91% for the OXAs, and between 47 and 96% for the ESAs. The maximum standard deviation of the absolute recoveries was 12%. The method detection limits are between 1 and 8 ng/L for the PCs, between 1 and 7 ng/L for the OXAs, and between 10 and 90 ng/L for the ESAs.

Acetanilides↗

PubMed1997

Characterization of specific immunoglobulin G (IgG) and its subclasses (IgG1 and IgG2) against the 23-valent pneumococcal vaccine in a healthy adult population: proposal for response criteria.

The aim of the study was to standardize an enzyme-linked immunosorbent assay (ELISA) method for the quantification of immunoglobulin G (IgG) and its subclasses (IgG1 and IgG2) against the 23-valent pneumococcal vaccine and to establish the criteria for a normal response to the vaccine. Forty healthy individuals (20 women and 20 men; mean age, 29 years) were studied. All were vaccinated with the 23-valent pneumococcal vaccine; blood samples were drawn just prior to and 3 weeks after immunization. Quantification of specific IgG and its subclasses was performed by an ELISA with the vaccine as the antigen. The linearity of the ELISA method was demonstrated by the similar slopes of the linear regression lines generated from the titration of sera with different antibody concentrations. The specificity of the antibodies against the vaccine was demonstrated by (i) an absorption test with pneumococcal vaccine, (ii) a cross-reactivity experiment with Haemophilus influenzae type b polysaccharide, and (iii) affinity chromatography with protein A-Sepharose. Response to the vaccine was defined by using the lower level of the 90% probability interval (one-tailed) for postimmunization-specific IgG, IgG1, and IgG2. By using this cutoff, responders were considered to be those with an absolute increase in antibody titers higher than 395 arbitrary units/ml for IgG, 0.350 A450 units for IgG1, and 0.314 A450 units for IgG2. Overall, 20 (50%) subjects had IgG, IgG1, and IgG2 responses, 9 (22.5%) had IgG and IgG2 responses, 4 (10%) had IgG1 responses, 3 (7.5%) had IgG and IgG1 responses, and 4 (10%) were nonresponders. Ninety percent of our population responded to the 23-valent pneumococcal vaccine. Up to 10% of healthy individuals may respond to an IgG subclass without significant increases in total IgG titers. The ELISA method that is described may be useful for evaluating the specific antibody response against polysaccharides.

Adult↗

PubMed1993

Ratio of dihydropyridine to ryanodine receptors in mammalian and frog twitch muscles in relation to the mechanical hypothesis of excitation-contraction coupling.

An indirect argument in favour of the mechanical hypothesis of excitation-contraction (EC) coupling [Schneider & Chandler (1973) Nature 242, 244-246] is the fixed stoichiometry between the voltage-driven dihydropyridine receptor (DHP-R) on the transverse tubule (TT) and the ryanodine-sensitive Ca2+ channel (RyR) of sarcoplasmic reticulum (SR) terminal cisternae (TC), based mainly on the structural arrangement described by Block et al. at junctional triads of toadfish swimbladder muscle [Block, B., et al. (1988) J. Cell Biol. 107, 2587-2600]. We calculated the overall DHP-R/RyR ratios for a wide variety of rabbit twitch muscles, as compared to fast- and slow-twitch muscles of the rat, and to frog sartorius, following quantification of high-affinity binding sites for tritiated PN200-110 and ryanodine. To this purpose, we carried out our binding measurements on both skeletal muscle membranes detached from myofibrils by extensive extraction with low-ionic strength medium, and on the myofibrillar residue containing a proportion of binding sites. Our results expressed per gram of muscle allow the following main conclusions: i) The overall DHP-R/RyR ratio is approximately 2 in both fast-twitch and slow-twitch muscle of the rabbit, implying that most, if not all, Ca(2+)-channels at junctional triads are stoichiometrically associated with the voltage sensor; in agreement with Block's model; ii) There is a major inconsistency in these values, rather than in the absolute values of RyR sites, on side by side comparison of fast-twitch and of slow-twitch muscles of the rabbit and rat, in that the DHP-R/RyR ratio is invariably lower for the rat, i.e., only about 1.2. Since the absolute values of DHP-R sites, according to our calculations, agree well with those obtained for the same muscles by Lamb & Walsh [(1987) J. Physiol. 393, 595-617], it seems improbable that they were underestimated. On the assumption that there is a fixed stoichiometry between DHP-R and RyR at the junctional contact area between TT and TC, the relatively large excess of RyR sites in the rat, expressed per g. muscle, should be attributed to the presence of a proportion of Ca(2+)-channels that are located outside this area, i.e., are extrajunctional [Dulhunty, A., et al. (1992) Proc. R. Soc. Lond. (B) 247, 69-75].(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2000

Analytical reliability of mobile-phase recycling in liquid chromatography

Although it is not officially condoned, mobile-phase (MP) recycling has become a widespread practice that is not well documented in terms of its effects on sample quantification. MP was spiked with three different concentrations of two analytes, tartaric acid and sodium citrate, to simulate MP recycling. These MPs were used to analyze eight different concentrations of these analytes in standard solutions. When analyte concentration in the MP exceeds that in the sample, a vacancy (negative) peak is observed, and when its concentration in the MP is equal to that in the sample, no peak is observed for that analyte. The slopes of the linear regression lines for standards in MPs with different concentrations of analyte did not change, although the gamma-intercept values decrease with increasing concentration of analyte in the MP. These results show that the concentration of analytes in recycled MP can be determined by comparing the absolute value of the gamma-intercept of the linear regression line with the corresponding peak area from the linear regression line for clean (solute-free) MP, provided other chromatographic parameters do not change. Suggestions are made for determining when recycled MP should be discarded.

Journal Article↗

PubMed2006

Evaluation of a method for assaying sulfonamide antimicrobial residues in cheese: hot-water extraction and liquid chromatography-tandem mass spectrometry.

Several sulfonamide antimicrobials (SAAs) are largely used in veterinary medicine. A rapid, specific, and sensitive procedure for determining 12 SAAs in cheese is presented. The method is based on the matrix solid-phase dispersion technique followed by liquid chromatography (LC)-tandem mass spectrometry (MS) equipped with an electrospray ion source. Target compounds were extracted from Mozzarella, Asiago, Parmigiano, Emmenthal, and Camembert cheese samples by 6 mL of water modified with 10% methanol and heated at 120 degrees C. The addition of methanol to hot water served to improve remarkably extraction yields of the most lipophilic SAAs, that is, sulfadimethoxine and sulfaquinoxaline. After acidification and filtration, 100 microL of the aqueous extract was injected in the LC column. MS data acquisition was performed in the multireaction monitoring mode, selecting two precursor-to-product ion transitions for each target compound. Methanol-modified hot water appeared to be an efficient extractant, because absolute recovery ranged between 67 and 88%. Using sulfamoxole as surrogate analyte, recovery of the 12 analytes spiked in the five types of cheese considered at the 50 ng/g level ranged between 75 and 105% with RSD not higher than 11%. Statistical analysis of the mean recovery data showed that the extraction efficiency was not affected by the type of cheese analyzed. This result indicates this method could be applied to other cheese types not considered here. The accuracy of the method was determined at three spike levels, that is, 20, 50, and 100 ng/g, and varied between 73 and 102% with relative standard deviations ranging between 4 and 12%. On the basis of a signal-to-noise ratio of 10, limits of quantification were estimated to be <1 ng/g.

Anti-Infective Agents↗

PubMed1992

Radiation-induced DNA single-strand breaks in freshly isolated human leukocytes.

Single-strand breaks are a major form of DNA damage caused by ionizing radiation, and measurement of strand breaks has long been used as an index of overall cellular DNA damage. Most assays for DNA single-strand breaks in cells rely on measuring fractionated DNA samples following alkali denaturation. Quantification is usually achieved by prelabeling cells with radioactive DNA precursors; however, this is not possible in the situation of nondividing cells or freshly isolated tissue. It has previously been demonstrated that the alkali unwinding assay of DNA strand breaks can be quantified by blotting the recovered DNA on nylon membranes and hybridizing with radiolabeled sequence-specific probes. We report here improvements to the technique, which include hot alkali denaturation of DNA samples prior to blotting and the use of carrier DNA that is non-complementary to the radiolabeled probe. Our method allows both single- and double-stranded DNA to be quantified with the same efficiency, thereby improving the sensitivity and reproducibility of the assay, and allows calibration for determination of absolute levels of DNA strand breaks in cells. We also used this method to assay radiation-induced DNA strand breaks in freshly isolated human leukocytes and found them to have a strand break induction rate of 1815 strand breaks/cell/Gy.

Carbon Radioisotopes↗

PubMed1995

Role of hepatic flavin-containing monooxygenase 3 in drug and chemical metabolism in adult humans.

In conjunction with asymmetric chemical syntheses and spectral, chiroptical, chromatographic and stereochemical correlation methods, we have developed procedures for the quantification of sulfoxide enantiomers and tertiary amine N-oxide diastereomer metabolites arising from the action of the adult human liver and other flavin-containing monooxygenases (FMOs). The parallel nature of the metabolic in vitro-in vivo studies and the use of chemical model oxidation systems allowed us to identify the FMO isoform involved. We investigated the enantioselective S-monooxygenation of cimetidine and the diastereoselective tertiary amine N-1'-oxygenation of (S)-nicotine as stereoselective functional probes of adult human liver FMO action. In both cases, the majority of evidence points to adult human liver FMO3 as the principal enzyme responsible for cimetidine S-oxygenation and (S)-nicotine N-1'-oxygenation in vitro and in vivo. The excellent agreement between the absolute configuration of the major cimetidine S-oxide and (S)-nicotine N-1'-oxide metabolites isolated from human urine and the major metabolite formed in the presence of adult human liver microsomes suggests that in vitro hepatic preparations may serve as a useful model for the in vivo condition. Further, that adult human liver cDNA-expressed FMO3 in Escherichia coli also gave the same absolute stereoselectivity (i.e. for (S)-nicotine N-1'-oxygenation) confirms the identity of the monoxygenase in vivo. Although we cannot rule out the involvement of minor contributions of cytochrome P-450 monooxygenases in cimetidine and (S)-nicotine oxidation, the majority of the data support the fact that cimetidine S-oxygenation and (S)-nicotine N-1'-oxygenation are stereoselective functional probes of adult human liver FMO3 activity. Finally, because the stereochemistry of the principal metabolite of cimetidine and (S)-nicotine in small experimental animals is distinct from that observed in humans, it is likely that species variation in predominant FMO isoforms exist and this may have important consequences for the choice of experimental animals in human preclinical drug design and development programs.

Adult↗

PubMed1991

Right and left lung perfusion: in vitro and in vivo validation with oblique-angle, velocity-encoded cine MR imaging.

Quantification of pulmonary flow is clinically important in the evaluation of both congenital and acquired heart disease. Velocity-encoded cine magnetic resonance (MR) is a promising technique for measuring velocity and volume of blood flow. The authors report validation of the accuracy of velocity-encoded cine MR for measurement of oblique-angle flow in vitro, with use of a constant-flow phantom, and in vivo, with nine healthy volunteers in whom velocities were measured separately in the main, right, and left pulmonary arteries. Findings at MR were compared with findings at Doppler echocardiography. Velocity measurements in a flow phantom with cine MR correlated well with direct measurements at Doppler echocardiography. Velocity-encoded cine MR enabled accurate and reproducible measurement of absolute blood flow in healthy subjects. Oblique-gradient flow encoding (ie, flow-encoding direction coinciding with the true direction of flow) was the method of choice for velocity measurements in the right and left pulmonary arteries.

Adult↗

PubMed1992

Investigation of nuclear c-MYC oncoprotein expression in human hematopoiesis: suitability of a rapid and reliable semiquantitative evaluation system.

The biologic functions mediated by the nuclear protooncogene, c-MYC are correlated to gene dosage. Since automated quantification programs are expensive, time-consuming and not easily available, and since analysis by flow cytometry is difficult in the case of nuclear antigens, we examined the suitability and reproducibility of a semiquantitative in situ evaluation system. This system was based on the percentage of nuclear area staining positively, and comprised the following categories: 0: negative, 1+: single scattered grains of the immunocytochemical staining product, 2+: confluence of grains to patches but less than 50% nuclear area positive, and 3+: greater than 50% positive nuclear area. In addition, sensitivity and specificity of two anti-c-MYC antibodies were investigated. Although both antibodies differed slightly in staining pattern and sensitivity, the four quantification categories were applicable for immunostainings of both antisera and highly reproducible when re-evaluated by the same observer (r = 0.98; p = 0.0001) or a second investigator (rAb155 = 0.98, rAb DCPm = 0.96; p = 0.0001), both reading blindly and independently. Comparing our semiquantitative evaluation categories and results of computer-assisted image analysis, the percentage of positive nuclear area (p less than 0.0001), the median staining intensity (p less than 0.0001), and the product of both (p less than 0.0001) differed significantly in the four evaluation categories. This result still held true after correction for nuclear size, which differed appreciably in various cell types (p less than 0.0001). The product of positive nuclear area, staining intensity and nuclear size (microns 2), which best approximates the absolute amount of c-MYC within a certain cell, was clearly different within the four staining categories (p less than 0.0001) and did not depend on cellular morphology within the staining categories 0 to 2. Also, the immunocytochemical technique proved highly reproducible (median day/day variance 0.65% (0-13); r = 0.995). The practicability of this system for semiquantification was demonstrated by (a) correlation of H score values of immunocytochemical stainings with densitometric scans of Western blots and (b) by the fact that peripheral blood lymphocytes, Phytohemagglutinin stimulated blasts, 13 cases of multiple myeloma and HL-60 cells differed concerning their estimated c-MYC amounts (p = 0.0125). This confirms on the effector molecule level results previously reported from mRNA in situ and Northern blotting analyses. We conclude that a simple and highly reproducible evaluation system can be used for in situ comparison of nuclear oncogene dosage.

Gene Expression↗

PubMed1997

Simplified quantification and reproducibility studies of dopamine D2-receptor binding with iodine-123-IBF SPECT in healthy subjects.

UNLABELLED: The purpose of this study was to assess the feasibility of a simplified SPECT scan protocol to quantify D2-receptor binding using [123I]iodobenzofuran (IBF) and to evaluate reproducibility of quantitative IBF-SPECT imaging without blood data. METHODS: Twenty healthy volunteers participated in the study, six had test/retest studies separated by 1 wk. Scans were acquired every 5 min for 180 min using a triple-headed SPECT camera after a bolus injection of IBF (292 MBq). The receptor parameter was determined by using our previously proposed variation of graphical analysis that derives the distribution volume ratio (Rv = V3/V2) from multiple scan data without blood data. Rv' was determined from three 20-min scan data obtained at 0-20, 50-70 and 160-180 min postinjection and compared with Rv as determined from scans obtained at 0-180 min. RESULTS: The mean Rv' (2.93 +/- 0.59) underestimated the mean Rv (3.10 +/- 0.50) by 5%. The mean variability (mean percent absolute difference) between Rv' and Rv was low (10%) with excellent reliability (intraclass correlation coefficient, p = 0.90). The relationship between Rv' and Rv was linear (r = 0.95, p < 10(-5)). The mean test/retest Rv and mean test/retest Rv' were (3.19 +/- 0.70/3.18 +/- 0.80) and (3.16 +/- 0.81/3.01 +/- 0.94), respectively, and these measures were not significantly different between test/retest studies. The mean test/retest variability of Rv was low (5%) with excellent reliability (p = 0.98). In addition, the mean test/retest variability of Rv' was low (10%) with excellent reliability (p = 0.94). CONCLUSION: Three short (20 min) IBF-SPECT scans allowing for rest periods between scans permit reliable measurements of the dopamine D2-receptor parameter V3/V2. Quantitative IBF-SPECT imaging without blood data is reliable and reproducible.

Adult↗

PubMed2005

Fusion of respiration-correlated PET and CT scans: correlated lung tumour motion in anatomical and functional scans.

Lower lobe lung tumours in particular can move up to 2 cm in the cranio-caudal direction during the respiration cycle. This breathing motion causes image artefacts in conventional free-breathing computed tomography (CT) and positron emission tomography (PET) scanning, rendering delineation of structures for radiotherapy inaccurate. The purpose of this study was to develop a method for four-dimensional (4D) respiration-correlated (RC) acquisition of both CT and PET scans and to develop a framework to fuse these modalities. The breathing signal was acquired using a thermometer in the breathing airflow of the patient. Using this breathing signal, the acquired CT and PET data were grouped to the corresponding respiratory phases, thereby obtaining 4D CT and PET scans. Tumour motion curves were assessed in both image modalities. From these tumour motion curves, the deviation with respect to the mean tumour position was calculated for each phase. The absolute position of the centre of the tumour, relative to the bony anatomy, in the RCCT and gated PET scans was determined. This 4D acquisition and 4D fusion methodology was performed for five patients with lower lobe tumours. The peak-to-peak amplitude range in this sample group was 1-2 cm. The 3D tumour motion curve differed less than 1 mm between PET and CT for all phases. The mean difference in amplitude was less than 1 mm. The position of the centre of the tumour (relative to the bony anatomy) in the RCCT and gated PET scan was similar (difference <1 mm) when no atelectasis was present. Based on these results, we conclude that the method described in this study allows for accurate quantification of tumour motion in CT and PET scans and yields accurate respiration-correlated 4D anatomical and functional information on the tumour region.

Algorithms↗

PubMed1992

SPECT versus planar scintigraphy for quantification of splenic sequestration of 111In-labelled platelets.

The splenic uptake of thrombocytes and spleen size were studied in 25 patients with idiopathic thrombocytopenic purpura (ITP) using two methods: anterior/posterior scintigraphy and single photon emission computed tomography (SPECT). Various factors (acquisition and reconstruction protocols) influencing the quality of 111In SPECT were studied. The splenic uptake, measured by SPECT, was found to be significantly higher in patients with a high level of autoantibodies in the blood than in patients without such antibodies (37 +/- 6%, n = 8 vs 22 +/- 3%, n = 11, P = 0.04, t-test). The correlation between the spleen SPECT volume and the geometric mean size in anterior and posterior images was 0.80 (P < 0.001). However, the spleen size calculated as geometric mean of anterior and posterior images differed by more than 50% from the SPECT volume in some patients. Based on these observations and on the results of phantom studies it is concluded that a reasonable estimate of the spleen:liver uptake ratio may be obtained using planar imaging, but to estimate the spleen volume and the absolute splenic uptake of platelets SPECT imaging is needed, in spite of the present technical limitations of SPECT.

Blood Platelets↗

PubMed1984

Energy consumption in a cyclic phosphorylation/dephosphorylation cascade.

Cyclic phosphorylation/dephosphorylation cascade systems are responsible for regulating numerous metabolic pathways. The capacity of a cyclic cascade system to maintain a steady-state level of phosphorylation and, hence, a specific biological activity of a phosphorylatable protein is dependent upon a constant supply of metabolic energy (ATP). Quantification of the extent of ATP consumption in a cyclic cascade was examined experimentally with the model in vitro phosphorylation/dephosphorylation system described in detail in the previous paper (Shacter, E., Chock, P. B., and Stadtman, E. R. (1984) J. Biol. Chem. 259, 12252-12259). The results indicate that (a) when the concentrations of converter enzymes and interconvertible substrate are held constant and the fractional phosphorylation of the substrate is varied by changing the allosteric effector concentrations, the rate of ATP consumption in the monocyclic cascade is directly proportional to the steady-state level of phosphorylation being maintained. (b) Attainment of a particular steady-state level of phosphorylation is determined by the net ratio of the protein kinase and phosphatase activities and is independent of the absolute concentrations of these enzymes. (c) Whereas the time required to reach a given steady state is inversely proportional to the converter enzyme concentrations, the amount of ATP consumed in maintaining that steady state is directly proportional to the kinase and phosphatase concentrations. In addition, a theoretical analysis based upon experimentally determined parameters for two in vivo cyclic cascade systems (pyruvate kinase and glycogen phosphorylase) revealed that under normal conditions, cyclic phosphorylation/dephosphorylation cascades consume only a small proportion (less than 0.02%) of the total cellular energy flux.

Adenosine Triphosphate↗

PubMed2006

Lung cancer: computerized quantification of tumor response--initial results.

PURPOSE: To prospectively quantify tumor response or progression in patients with lung cancer by using thin-section computed tomography (CT) and a semiautomated algorithm to calculate tumor volume and other parameter values. MATERIALS AND METHODS: This HIPAA-compliant study was institutional review board approved; informed patient consent was waived. CT scans of 15 measurable non-small cell lung cancers (in five men and 10 women; mean age, 64 years; range, 38-78 years) before and after gefitinib treatment were analyzed. A semiautomated three-dimensional lung cancer segmentation algorithm was developed and applied to each tumor at baseline and follow-up. The computer calculated the greatest diameter (unidimensional measurement), the product of the greatest diameter and the greatest perpendicular diameter (bidimensional measurement), and the volume of each tumor. Exact McNemar tests were used to analyze differences in the percentage change calculated with different measurement techniques. RESULTS: The computer accurately segmented 14 of the 15 tumors. One paramediastinal tumor required manual separation from the mediastinum. Eleven (73%) of the 15 patients had an absolute change in tumor volume of at least 20%, compared with one (7%) and four (27%) patients who had similar changes in unscaled unidimensional (P < .01) and bidimensional (P = .04) tumor measurements, respectively. Seven (47%) patients had an absolute change in tumor volume of at least 30%. In contrast, at unscaled analysis, no patients at unidimensional measurement (P = .02) and two (13%) patients at bidimensional measurement (P = .06) had a change of at least 30%. CONCLUSION: Compared with the unidimensional and bidimensional techniques, semiautomated tumor segmentation enabled the identification of a larger number of patients with absolute changes in tumor volume of at least 20% and 30%.

Adult↗