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Results for “Absolute quantification”

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PubMed1986

Potential problems in serum protein electrophoresis.

Potential problems are described that one could encounter in carrying out an electrophoretic procedure including its ancillary phases of visualization (staining) and quantification (densitometry). Endpoint-like measurements for separated isoenzymes may provide artifactual kinetic values as well, because stain measurement is fixed at a single time whereas reagent blanking in the electrophoretic medium is substituted for the conventional serum initial absorbance readings of test-tube determinations. Truncation of separated electrophoretic zones or opacity of an electrophoretic anti-convection medium such as uncleared cellulose acetate may also interfere with absolute quantification procedures.

Albumins↗

PubMed1992

SPECT quantification: a simplified method of attenuation and scatter correction for cardiac imaging.

The quantitative and visual interpretation of SPECT myocardial perfusion images is limited by physical factors such as photon attenuation, Compton scatter, and finite resolution effects. A method of attenuation correction is described for use in nonhomogeneous media and applied to cardiac SPECT imaging. This method, termed multiplicative variable attenuation compensation (MVAC), uses tissue contours determined from segmentation of a transmission scan to assign a priori determined attenuation coefficients to different tissue regions of the transaxial images. An attenuation correction map is then constructed using a technique inspired by Chang's method that includes regionally dependent attenuation within the chest cavity and is applied after reconstruction by filtered backprojection. Scatter correction using the subtraction of a simultaneously acquired scatter window image enables the use of narrow beam attenuation coefficients. Experimental measurements to evaluate these methods were conducted for 201Tl and 99mTc SPECT using a homomorphic cardiac phantom. Finite resolution effects were included in the evaluation of results by computer simulation of the three-dimensional activity distribution. The correction methodology was shown to substantially improve both relative and absolute quantification of uniform and nonuniform regions of activity in the phantom's myocardial wall.

Heart↗

PubMed1988

A critical assessment of methods of measuring metabolite concentrations by NMR spectroscopy.

Many NMR studies are made by scientists and clinicians in order to measure metabolite levels. There is a growing need to obtain absolute quantification of these metabolites. We have therefore reviewed the methods that are available and those which are being developed, for studies in vivo and on isolated tissues. We describe the following methods and assess their advantages and limitations: (1) Conventional spectroscopy and area ratios, (2) Tissue extracts, (3) External capillary, (4) Internal endogenous marker, (5) Internal exogenous marker, (6) External marker in bath, (7) Reference to internal 1H water concentration, (8) Gradient-localized spectroscopy and (9) Fourier series analysis localization. The relevant biological and technical aspects associated with quantification of metabolite concentrations are also discussed. This includes NMR visibility, origin of the NMR signals, definitions of concentration, influence of the RF coil, data collection and data analysis.

Humans↗

PubMed1992

Absolute quantitation of gallium-67 citrate accumulation in the lungs and its importance for the evaluation of disease activity in pulmonary sarcoidosis.

Our modification of a method for the absolute quantification of gallium-67 uptake in lungs with a scintillation camera and computer is described. The uptake of 67Ga in lungs, expressed in percentage of administered radioactivity, was determined by the transmission-emission method. We proved theoretically and experimentally that a 67Ga planar source could be replaced with a 57Co planar source. The performance of lung perfusion scans allows a more accurate delineation of the regions of interest on gallium scans. The method was applied to control subjects (n = 27) and to patients (n = 114) suffering from biopsy-proven pulmonary sarcoidosis (28 with inactive and 86 with active disease). The obtained results were compared with chest X-ray findings, the percentage of lymphocytes in the bronchoalveolar fluid (BAF-ly%), and serum angiotensin-converting enzyme (SACE) values. The method seems suitable for the assessment of disease activity in sarcoidosis. It is more accurate in detecting parenchymal involvement in lung sarcoidosis than the commonly used X-ray criteria. No correlation was found between 67Ga uptake and the BAF-ly% and SACE values.

Bronchoalveolar Lavage Fluid↗

PubMed2026

Comprehensive quality profiling and comparative metabolic characterization of seven dominant fresh-eating Chinese olive (Canarium album Lour.) cultivars in Southern China.

Fresh-eating Chinese olive (Canarium album Lour.) is a subtropical fruit endemic to southern China with considerable commercial value, yet systematic quality characterization of dominant cultivars remains scarce. This study established a multi-dimensional quality dataset for seven dominant cultivars from Fujian and Guangdong provinces, integrating nutritional components, soluble sugars, organic acids, mineral elements, volatile profiles, and non-targeted metabolomics. Significant cultivar-specific differences were observed across all evaluated dimensions: "Lingfeng" exhibited a sugar-dominant low-acid profile, whereas "Sanleng" showed elevated phenolic constituents accumulation. Volatile profiling identified terpenoid-based candidate discriminatory biomarkers, and metabolomic analysis revealed phenylpropanoid biosynthesis, tryptophan metabolism, and starch and sucrose metabolism as the most variable pathways. Correlations between untargeted profiling and targeted absolute quantification validated untargeted result reliability and revealed their complementarity in nutritional evaluation. These findings provide baseline data for FECO germplasm evaluation and targeted industrial utilization.

China↗

PubMed2026

Quantitative proteomics of molybdenum cofactor biosynthesis and utilization in Caenorhabditis elegans.

The molybdenum cofactor (Moco) is a chemically labile prosthetic group required by a small but essential set of metazoan enzymes, including sulfite oxidase, xanthine dehydrogenase, aldehyde oxidases, and the mitochondrial amidoxime reducing components (MARC). Disruption of Moco biosynthesis in humans causes Molybdenum Cofactor Deficiency (MoCD), a severe neonatal encephalopathy. Caenorhabditis elegans is unique among animals studied so far in that it can meet its Moco requirement through both endogenous biosynthesis and direct uptake of mature Moco from its bacterial diet. However, the organism-wide abundance of the Moco biosynthetic machinery and Moco-dependent enzymes, and their response to altered Moco supply, have remained unknown. Here, using data independent acquisition proteomics with histone anchored absolute quantification, we generated an organism wide quantitative atlas of Moco biosynthesis and utilization in C. elegans under standard and Moco limiting conditions. Components of the biosynthetic pathway showed a strikingly asymmetric abundance. The mitochondrial enzyme MOC-5, which catalyzes the first committed step in Moco biosynthesis, was present at only about 120 copies per genome equivalent, roughly fifty-fold below the downstream cytoplasmic biosynthetic machinery, which ranged from about 5,000 to 8,500 copies per genome equivalent, identifying MOC-5 as a stoichiometric bottleneck. On the utilization side, the MARC paralogs were the dominant Moco consumers, with MARC-1 exceeding 20,000 copies per genome equivalent. Loss of dietary or endogenous Moco selectively depleted the nonsulfurated clients SUOX-1 and MARC-1, whereas biosynthetic proteins remained unchanged, indicating that protein stability, rather than compensatory expression, is the main response to Moco limitation.

Caenorhabditis elegans↗

PubMed1991

[Modern nuclear medical diagnosis as applied pathophysiology. Basis and outlook].

In their capacity as "image-assisted functional diagnostics", methods of nuclear medicine link morphological patterns of radiology with clinical presentation. Based on pathophysiology they supply an insight into both global and regional parameters, present as basal values or as reserves. Both, single photon emission computed tomography (SPECT) or highly defined positron ECT (PET), enabled computer-assisted topographical overlay and thus an exact comparative evaluation of regional function versus morphology. In addition, PET gives access to a true physiological, absolute quantification employing process specific, carrier-free substrates. Novel tracers (markers of metabolism or perfusion, receptors or transmitter substances, monoclonal antibodies), an intraluminal transport model and the concept of buffer or working reserves aim at conducting early diagnosis, determination of disease severity and parameters that are relevant for therapy, on a level that is pathophysiologically oriented.

Brain Diseases↗

PubMed2025

StrainR2 accurately deconvolutes strain-level abundances in synthetic microbial communities.

MOTIVATION: Synthetic microbial communities offer an opportunity to conduct reductionist research in tractable model systems. However, deriving abundances of highly related strains within these communities is currently unreliable. 16S rRNA gene sequencing does not resolve abundance at the strain level and other methods such as quantitative polymerase chain reaction (qPCR) scale poorly and are resource prohibitive for complex communities. We present StrainR2, which utilizes shotgun metagenomic sequencing to provide high accuracy strain-level abundances for all members of a synthetic community, provided their genomes. RESULTS: Both in silico, and using sequencing data derived from gnotobiotic mice colonized with a synthetic fecal microbiota, StrainR2 resolves strain abundances with greater accuracy and efficiency than other tools utilizing shotgun metagenomic sequencing reads. We demonstrate that StrainR2's accuracy is comparable to that of qPCR on a subset of strains resolved using absolute quantification. AVAILABILITY AND IMPLEMENTATION: Software is available at GitHub and implemented in C, R, and Bash. Software is supported on Linux and MacOS, with packages available on Bioconda or as a Docker container. The source code at the time of publication is also available on figshare at the doi: 10.6084/m9.figshare.29420780.

Mice↗

PubMed1988

Quick sampling and perpendicular cryosectioning of cell monolayers for the X-ray microanalysis of diffusible elements.

A quick sampling and preparation method for freezing of cell monolayers is described. The cells are grown on a large Formvar film supported by a frame of polystyrene. A polyvinylpyrrolidone (PVP) solution is applied to one side of the film forming a flat disc when frozen with a pair of pliers precooled in liquid nitrogen. The PVP solution provides the specimen with sufficient strength and may be used as an elemental standard for absolute quantification if salts of known concentrations are added. Manipulation of the cells prior to freezing is thus restricted to a minimum, which eliminates possible harmful treatments like scraping and centrifugation. The procedure is quickly performed, the freezing being completed within 30 s of the cells having been removed from the culture well. The analytical results reveal low and stable Na:K ratios. Our results confirm that cells in vitro are comparable to cells in vivo with respect to elemental composition.

Adenocarcinoma↗

PubMed1976

The Mark IV system for radionuclide computed tomography of the brain.

The Mark IV scanning system is a simple four-sided arrangement of 32 independent detectors which rotate continously as a unit, detecting, processing, and displaying the reconstructed data while the study progresses. Detection is by single photon counting and is compatible with commercially available radionuclides. An empirical correction is applied for attenuation, difference in detector response, and scatter. It is a high-sensitivity device with approximately uniform resolution throughout the section plane. There is good reproducibility and accuracy for absolute quantification of radionuclide concentration in the brain. Clinical applications include scans of 99mTcO4, 99mTc-RBC, 123I-iodoantipyrine, 99mTc-diphosphonate, and 111In-DTPA.

Adolescent↗

PubMed2023

Comprehensive quantitative modeling of translation efficiency in a genome-reduced bacterium.

Translation efficiency has been mainly studied by ribosome profiling, which only provides an incomplete picture of translation kinetics. Here, we integrated the absolute quantifications of tRNAs, mRNAs, RNA half-lives, proteins, and protein half-lives with ribosome densities and derived the initiation and elongation rates for 475 genes (67% of all genes), 73 with high precision, in the bacterium Mycoplasma pneumoniae (Mpn). We found that, although the initiation rate varied over 160-fold among genes, most of the known factors had little impact on translation efficiency. Local codon elongation rates could not be fully explained by the adaptation to tRNA abundances, which varied over 100-fold among tRNA isoacceptors. We provide a comprehensive quantitative view of translation efficiency, which suggests the existence of unidentified mechanisms of translational regulation in Mpn.

RNA, Transfer↗

PubMed2026

Protein Profiling Identifies Biomarkers for Predicting Disease Severity in Anti-NMDAR Encephalitis.

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a severe autoimmune neurological disorder characterized by pathogenic antibodies against the NMDAR. A systematic protein profiling approach is warranted to identify biomarkers capable of predicting disease status. An Olink proximity extension assay (PEA) profiled 91 inflammation-related proteins from anti-NMDAR encephalitis patients. Disease severity or prognosis were assessed by CASE score or mRS score at 6-month follow-up. Patients were stratified into distinct molecular clusters using unsupervised clustering. Logistic regression models incorporating selected biomarkers were developed to predict disease severity and prognosis, followed by absolute quantification using ELISA. Patients were classified into four consensus clusters. Clusters 1 and 2 corresponded to the mild group, while Cluster 3 represented the severe group, consistent with CASE score above 6. Cluster 4 showed heterogeneous clinical features. Elevated serum levels of IL-10, IL-6, and SIRT2, as well as increased CSF levels of CXCL10, CXCL11, and MMP10, were positively associated with severe disease. Conversely, several proteins including LTA and CCL11, CCL8, TGFB1, CXCL6 were associated with severe disease or unfavorable 6-month outcomes. A logistic regression model combining serum CXCL6 and CCL11 with CSF MMP10 achieved an area under the curve (AUC) of 0.95 for predicting disease severity. Serum CCL11 alone showed predictive value for 6-month prognosis, with an AUC of 0.79. These findings delineate distinct protein signatures associated with clinical heterogeneity of anti-NMDAR encephalitis. Prediction models incorporating multiple biomarkers may provide an approach for disease severity stratification and prognosis forecast.

Humans↗

PubMed2026

[Laryngeal squamous cell carcinoma-derived exosomes promote neuronal axonal growth by remodeling the neural microenvironment].

Objective: Perineural invasion (PNI) is a critical determinant of poor prognosis in laryngeal squamous cell carcinoma (LSCC), but its underlying mechanisms remain unclear. This study aimed to investigate whether LSCC-derived exosomes induce axonal growth by delivering neuroactive molecules, thereby contributing to tumor perineural invasion. Methods: Clinical data from the laryngeal cancer cohort of The Cancer Genome Atlas Head and Neck Squamous Cell Carcinoma (TCGA-HNSC) dataset were analyzed. Propensity score matching (PSM) and Cox regression were used to evaluate the prognostic value of nerve density, and these findings were validated using 35 pairs of laryngeal cancer and adjacent normal tissue specimens collected at Yantai Yuhuangding Hospital between 2022 and 2026 to assess neural morphological changes. Exosomes were isolated from the human LSCC cell line AMC-HN-8, characterized by quality-control assays, and co-cultured with PC12 cells. A rescue experiment using GW4869, a specific inhibitor of neutral sphingomyelinase, was performed to confirm the exosome-dependent effect. Neurite outgrowth was evaluated by immunofluorescence, and the expression of axonal growth-related genes was measured by RT-qPCR. Targeted metabolomics was employed for the absolute quantification of neuroactive metabolites within the vesicles and for pathway enrichment analysis. Results: After PSM adjustment, high nerve density was identified as an independent poor prognostic factor in LSCC patients (HR=2.10, P=0.035), with particularly pronounced prognostic value in the early-stage node-negative (N0) subgroup (HR=4.07, P=0.001). Pathological sections showed high expression of the neural markers βIII-tubulin and PGP9.5 in LSCC tissues (βIII-tubulin: t=2.234, P<0.05; PGP9.5: t=2.575, P<0.05). Exosomes were successfully isolated from AMC-HN-8 cells and passed quality control. In vitro assays showed that LSCC-derived exosomes significantly promoted neurite extension and branching in PC12 cells (t=4.147, P<0.000 1) and upregulated core axonal growth genes, including GAP-43, NEFL, and NEFM (GAP-43: t=3.698, P<0.05; NEFL: t=5.113, P<0.01; NEFM: t=5.263, P<0.01); this effect was completely reversed by the exosome-release inhibitor GW4869 (t=3.535, P<0.001). Targeted metabolomics revealed a specific enrichment of 12 neurotransmitters and metabolites within LSCC exosomes, centered on glutamine (83.411 μmol/L, FC=1.88) and glutamate (18.461 μmol/L, FC=1.21), which were significantly enriched in signaling pathways such as "central carbon metabolism in cancer" and "glutamatergic synapse". Conclusion: Nerve density is a potential adverse prognostic factor in patients with LSCC. LSCC-derived exosomes can directly induce axonal growth in neuron-like cells, suggesting that tumor cells actively remodel the neural microenvironment and drive axonal growth through exosome-mediated long-range signaling.

Exosomes↗

PubMed1992

[Positron emission tomography in cardiological diagnosis: principles and clinical application].

Positron emission tomography (PET) is an emerging new cardiac imaging modality which allows sophisticated tissue characterization using radiopharmaceuticals. This technique provides absolute quantification of regional tracer concentration using short-lived isotopes such as carbon-11, oxygen-15 and nitrogen-13, which can be easily incorporated in many compounds without changing their biological behaviour. These technical advantages are somewhat offset by the high cost of this technology which includes camera as well as on site cyclotron required for the preparation of radiopharmaceuticals. Recent clinical dates suggest that unique information can be obtained with PET. Using blood flow tracers in combination with PET, coronary artery disease can be detected and localized with high diagnostic accuracy. First studies comparing Tl-201 SPECT and PET in the same patient population indicate diagnostic superiority of PET. In combination with tracer kinetic models, regional myocardial blood flow can be quantitated and the functional significance of coronary artery stenosis defined by regional coronary reserve measurements. The assessment of regional glucose metabolism by PET with the tracer F-18 deoxyglucose has received wide clinical acceptance. Metabolic imaging in patients with advanced coronary artery disease allows the delineation of ischemically compromised but viable myocardium. Selection of patients for revascularization based on this scintigraphy tissue characterization has been shown to have a high predictive value for subsequent tissue recovery. Comparison of PET/FDG imaging with thallium-201 scintigraphy for assessment of tissue viability indicate that, in patients with fixed thallium-201 defects, additional diagnostic information can be obtained by this more expensive technology.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiomyopathies↗

PubMed1991

[Localized nuclear magnetic resonance spectroscopy in vivo. Physical principles and quantitative problems].

Recent technological developments extended the use of nuclear magnetic resonance to clinical imaging (MRI), as well as to in vivo metabolic studies on tissues and organs by means of localized spectroscopy (MRS). The quantitative determination of absolute metabolic concentrations by in vivo MRS still represents a challenge for technological efforts and biochemical investigations. In fact, the different methodologies today available for spectral acquisition from localized regions within a body organ or pathological lesion should ideally lead to a complete suppression of signals from surrounding tissues, without any appreciable signal loss from the volume of interest. Accurate assessment of deviations of the real from the ideal case represents an essential requirement for either relative or absolute quantification of in vivo localized MR spectra. A review will be presented of the most utilized MRS methodologies, together with a discussion on their potentialities and limitations. Techniques have been classified according to the use of either r.f. (B1) and/or static magnetic field (B0) gradients. The last session will be devoted to the presentation of some results obtained in our laboratory on the use of a particular test-object (constructed at the Deft Institute of Technology) for assessing signal localization efficiency provided by a surface coil in a small scale MRS/MRI equipment (for in vivo biochemical studies on small animals). The surface coil was used in conjunction with a number of sequence (t1-90 degrees-acq; 1-D "chemical shift imaging"; "depth") of either square or adiabatic r.f. pulses. The results allow the selection, on a quantitative basis, of the most appropriate pulse sequence(s) to be used for metabolic studies on superficial experimental tumours (implanted s.c. in small animals), according to the mean area and thickness of the neoplastic lesion. The latter parameters can be non-invasively assessed by previous MRI analysis of the tumour. This study was carried out in the frame of the EC COMAC-BME Concerted Research Project on Tissue Characterization by MRS and MRI.

Animals↗

PubMed1986

Alterations of energy metabolism in the spontaneously hypertensive rat: a 31P nuclear magnetic resonance study.

We quantified high-energy phosphate metabolites in hypertensive hypertrophied and normal myocardium and monitored temporal changes using the non-invasive 31P nuclear magnetic resonance (NMR) spectroscopy. Hearts from 18 month spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto rats (WKY) were perfused with a phosphate-free buffer at 10 cc/min per g and paced at 240 beats/min on a modified Langendorff apparatus. Perfusion pressure, left ventricular pressure (LVP) and dP/dt were recorded and successive 31P NMR spectra were collected during a 24-min baseline period (oxygenated buffer), anoxia (N2-bubbled and glucose-free buffer) until a 70% fall in LVP occurred, and recovery. An aminomethylphosphonate standard, located within the LVP balloon, permitted absolute quantification of myocardial phosphate moieties (including inorganic phosphate (Pi), creatine phosphate (CP) and ATP). During perfusion, SHR hearts demonstrated higher coronary resistance but no significant differences in LVP or dP/dt. Spontaneously hypertensive rat hearts had lower CP, ATP and CP/Pi ratio and showed a faster fall in cardiac function during anoxia, associated with parallel rates of changes in the phosphate moieties.

Animals↗

PubMed1975

Measurement of absolute amounts of antigen-specific human IgE by a radioallergosorbent test (RAST) elution technique.

A technique for the absolute quantification of antigen-specific human IgE is described. It employs elution of a calculable amount of antigen-specific IgE from an allergosorbent-antibody complex by means of alkaline pH treatment, followed by measurement of the IgE content of the eluate with a modified radioimmunosorbent test (RIST). With this method IgE antibody directed against the benzylpenicilloyl determinant of penicillin (BPO) was measured quantitatively in sera from seven penicillin allergic patients. IgE specific for ragweed antigen E was measured in sera from 33 ragweed allergic patients. Values obtained for IgE anti-BPO ranged from 19 to 1806 ng/ml and comprised from 1.3 to 27.5% of total serum IgE. Values of IgE anti-antigen E ranged from 9 to 1807 ng/ml, comprising from 3 to 84% of total serum IgE. Excellent correlation (r = 0.99; p less than 0.001) was obtained for both antigen systems between values determined by the RAST elution technique and by simple RAST assay with interpolation from a reference serum of known specific IgE content as determined by the elution technique may be needed only for primary standardization of reference sera.

Allergens↗

PubMed1989

In vivo assessment of a digital angiographic method to measure absolute coronary artery diameters.

Several techniques exist for the quantification of absolute coronary artery diameters using radiologic methods. An in vivo assessment of a quantitative technique based on direct digitally acquired images was performed by imaging inflated angioplasty balloons (n = 25), balloon catheter shafts (n = 16) and coronary guidewires (n = 20) at the time of coronary angioplasty. After this, the actual size of the objects was determined with a micrometer. Diameters measured by the quantitative digital method had an excellent correlation with the actual diameters (digital diameter = 0.80 [actual diameter] + 0.32; n = 61; r = 0.97; standard error of the estimate = 0.26 mm; p less than 0.001). Moreover, the correlation between interobserver and intraobserver measurements was excellent (r = 0.99 for both, standard error of the estimate = 0.16 mm and 0.09 mm, respectively). However, there was a consistent error present that was related to the size of the object measured. Objects less than 0.5 mm were consistently overestimated and objects greater than 1 mm were usually underestimated by the digital technique, although the actual magnitude of the error was small. Objects less than 0.5 mm in diameter were overestimated by 0.41 +/- 0.11 mm and objects greater than 1 mm were underestimated by 0.23 +/- 0.19 mm. Based on an analysis of the error present, correction algorithms were formulated and tested prospectively using an additional 29 object measurements. This resulted in an improvement in the quantification of the diameters with a smaller magnitude of error. This in vivo assessment suggests that the rapid online assessment of absolute coronary artery diameters is possible, but also demonstrates important errors inherent in this method.

Algorithms↗