SEARCH · PubMed Health

Results for “Absolute quantification”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37Linked to original sources

PubMed2003

Flow cytometric analysis of T cell proliferation in a mixed lymphocyte reaction with dendritic cells.

BACKGROUND: Dendritic cells (DCs) are the most potent antigen-presenting cells. They can be generated in vitro from CD14+ cells, and also from CD34+ progenitor cells. Although T cell proliferation using [3H] thymidine incorporation assay has been used widely to check DC function, this technique only provides limited information about the T cell proliferation. Here, we describe a novel method for quantitative analysis of T cell proliferation using flow cytometry. MATERIALS AND METHODS: DCs were generated from CD14+ cells from six healthy blood donors. Monocytes were isolated using positive selection with magnetic cell sorting (MACS) and then cultured with IL-4, GM-CSF, IL-1beta, IL-6, TNF-alpha and PGE(2) to yield fully mature DCs. Allogeneic naive T lymphocytes with known mismatches in HLA classes I and II were cocultured with DCs. Naive T cells without DC stimulation served as negative controls. T cells were harvested on days 0, 3, 5, 7, 9, 11 and analysed by flow cytometry. CD3-ECD and CD4-fluorescein isothiocyanate (FITC) or CD8-FITC antibodies were used to distinguish T cell subsets, whereas T cell activation was measured by assessment of HLA-DR, CD45RO, CD25 and CD71 expression. For T cell quantification, fluorescent microparticles were used. Dead cells were excluded with 7-AAD. The bromdeoxyridine (BrdU)-incorporation ELISA procedure was also performed in order to compare with the T cell proliferation assay with regard to absolute cell counts and CD71 expression. RESULTS: The initial T cell concentration on day 1 was 203.9+/-39.7 (173-265) CD3+/CD4+ cells/micro l and 184.5+/-41.6 (148-260) CD3+/CD8+ cells/micro l. The maximal T cell proliferation was recorded on day 7 with a five- to tenfold T cell expansion which resulted in 1994.9+/-383 (1446-2404) CD3+/CD4+ cells/micro l and 944+/-303.7 (560-1483) CD3+/CD8+ cells/micro l. Furthermore, activation markers of both cell lineages were upregulated and reached maxima on days 7 (CD71) and 9 (CD25, HLA-DR). T cell count/micro l as well as CD71 expression both correlated significantly with BrdU incorporation. CONCLUSION: Flow cytometric analysis permits simple, precise and rapid quantification of T cell proliferation in a mixed lymphocyte reaction with DCs. Activation, proliferation and cell viability can be simultaneously determined. CD71 is particularly well suited as an activation marker for the simultaneous measurement of T cell proliferation. Thus, specific T cell subsets involved in antigen-specific proliferation can be evaluated in detail.

Bromodeoxyuridine↗

PubMed1998

Plasma indomethacin assay using high-performance liquid chromatography-electrospray-tandem mass spectrometry: application to therapeutic drug monitoring and pharmacokinetic studies.

The authors report the use of high-performance liquid chromatography-electrospray-tandem mass spectrometry (HPLC-ESI-MS/MS) for the quantification of indomethacin (IND) in plasma with microscale sample preparation. Plasma samples (100 microL) and mefanamic acid (internal standard [IS]), buffered to pH 3.5, were prepared using solid phase extraction and chromatographed using a C8 column. The mobile phase composition was 80% methanol to 20% ammonium acetate buffer (40 mM, pH 5.1). A flow rate of 300 microL per minute was used with a 1-to-12 postcolumn split into the mass spectrometer. Selected reaction monitoring with mass transitions m/z 357.9-->139.0 and m/z 242-->209.0 were used for IND and IS, respectively. The chromatographic analysis time was 4 minutes. The assay was linear from 5 microg/L to 2000 microg/L with interday imprecision (n=5) over the analytic range (5%). At four concentrations (10 microg/L, 25 microg/L, 250 microg/L, 1500 microg/L), assay imprecision was 9% (total coefficient of variation [CV]) and accuracy ranged between 96.5% and 102.8% (n=16). The absolute recovery of IND and IS was 74% (n=8) and 95% (n=24), respectively. This method was developed and validated in less than 10 working days, had a lower limit of quantification than reported HPLC-ultraviolet (UV) methods, and uses small sample volumes. These factors illustrate the power of HPLC-ESI-MS/MS for drug analysis. Furthermore, the ability of this method to measure IND over a wide concentration range makes it suitable for therapeutic drug monitoring and pharmacokinetic studies.

Chromatography, High Pressure Liquid↗

PubMed2026

Longitudinal Prediction of Retinal Sensitivity Based on Disease Progression Quantified From Optical Coherence Tomography in Geographic Atrophy.

PURPOSE: The purpose of this study was to analyze the association between disease progression of geographic atrophy (GA) from optical coherence tomography (OCT) with retinal sensitivity (RS) in microperimetry (MP) over a 2-year follow-up period. METHODS: This is a longitudinal analysis of the OAKS Phase-III clinical trial. Both study and fellow eyes with GA that underwent imaging with the Spectralis OCT and consecutive MP examination were eligible. Pointwise quantification of ellipsoid zone (EZ) thickness, EZ and retinal pigment epithelium (RPE) loss from OCT volumes was correlated with localized RS. A longitudinal predictive model using a Markov Chain framework was implemented to predict RS change over time based on OCT biomarkers. The modeling of morphological and functional progression was based on the fellow-eye cohort. RESULTS: A total of 39,681 MP points from 406 patients were analyzed. In the fellow eye cohort, baseline (BSL) EZ thickness was positively associated with RS (0.3 decibel [dB]/µm, P < 0.001). Decrease in EZ thickness between visits during follow-up was significantly associated with decrease in RS (0.1 dB / 1 µm change). RS was significantly lower in MP points within EZ loss during follow-up compared with MP points within the retina with measurable EZ (P < 0.001). The largest functional decline was observed within RPE loss, also associated with the highest probability of absolute scotoma (P < 0.001). Morphological progression to EZ and RPE loss was influenced by EZ thickness and the morphology of adjacent MP points (P < 0.001). CONCLUSIONS: Two exploratory endpoints were developed, namely quantification of EZ thickness and loss, and localized RS within high-risk OCT areas. RS decline during follow-up is associated with automatically quantified disease progression in OCT.

Humans↗

PubMed1999

HIV-1 in semen: determination of proviral and viral titres compared to blood, and quantification of semen leukocyte populations.

This study was carried out to determine the relationship between proviral DNA and viral RNA titres in semen compared with blood. In addition, the association between semen leukocyte counts with detection frequency and absolute levels of human immunodeficiency virus type 1 (HIV-1) nucleic acids was also assessed. Paired samples of blood and semen were collected from a cohort of individuals with different blood CD4 cell counts, and whose anti-HIV therapy had not changed in the preceding 3 months. The cell-associated proviral DNA titres and cell-free plasma viral RNA titres were determined using nested primer polymerase chain reaction and NASBAtrade mark, respectively. In addition, leukocyte counts were determined by immunocytochemical and cytochemical staining of a subset of semen samples. HIV-1 proviral DNA was detected in 100% and 47%, and viral RNA was detected in 76% and 63%, of blood and semen samples tested, respectively. HIV-1 proviral DNA and viral RNA titres in blood were higher than in corresponding semen samples, although the difference observed in viral RNA titres was not statistically significant. Proviral DNA and viral RNA titres were correlated between the two body fluids, and within the semen, although some individuals had disparate semen and blood titres or detection rates, indicating genital tract compartmentalisation. In addition, detection of HIV-1 proviral DNA, but not of HIV RNA, in semen was associated with elevated semen leukocyte counts, although this latter finding requires verification in future studies of larger numbers of patients.

CD4 Lymphocyte Count↗

PubMed2005

Preparative enantiomeric separation of new aromatase inhibitors by HPLC on polysaccharide-based chiral stationary phases: Determination of enantiomeric purity and assignment of absolute stereochemistry by X-ray structure analysis.

The development of high-performance liquid chromatography methods on polysaccharide-based stationary phases (cellulose or amylose derivatives) has permitted preparative enantioseparations of various 6-[1(imidazol-1-yl)-1-phenylmethyl]-3-methyl-1,3-benzoxazol-2(3H)-one and 6-[1(imidazol-1-yl)-1-phenylmethyl]-3-methyl-1,3-benzothiazol-2(3H)-one, aromatase inhibitors, with satisfactory yields. Analytical enantioseparation methods using both UV and evaporative light-scattering detection (ELSD) were validated to determine the enantiomeric purity of these compounds. Using UV detection, linear calibration curves in the range from 4 x 10(-6) to 4.8 x 10(-4) M range were obtained; repeatability, limits of detection (LD), and quantification (LQ) were determined: LD varied, for the various solutes, from 1 to 80 microg/l and from 2.05 to 10.05 mg/l with UV detection and ELSD, respectively. Single-crystal X-ray analysis was successful in determining the absolute configuration of the individual enantiomers. The relationship between retention order and absolute configuration of the enantiomers was established.

Aromatase Inhibitors↗

PubMed2000

Standardized flow cytometric method for the accurate determination of platelet counts in patients with severe thrombocytopenia.

BACKGROUND: The therapeutic option of prophylactic platelet (PLT) transfusion in cases of severe thrombocytopenia critically depends on the availability of accurate and precise counts because clinical decisions are widely based on decision or trigger points. Although often applied in current practice at a level of 20 Gpt/L, there is increasing evidence that the trigger points could safely be reduced to 10 or even 5 Gpt/L. In order to facilitate this downward revision, it is necessary to have PLT counting methods that are able to provide reliable results in the appropriate decision range. METHODS: Postchemotherapy-induced pancytopenia PLT counting was performed in patients with hematological malignant disorders. This study describes a novel flow cytometric method that utilizes a PLT-specific monoclonal antibody (CD41a) in conjunction with fluorescent reference beads in order to derive absolute platelet numbers. RESULTS: Applying a mathematical model, this flow cytometric method was shown to have a detection limit of 0.24 Gpt/L and a lower limit of quantification (coefficient of variation [CV] = 10%) of 1.1 Gpt/L. These values are a substantial improvement on previously reported results for the Technicon H1 automated instrument or manual hemocytometry. Moreover, although the flow cytometry and Technicon H3 methods were found by supplementary analyses to show a reasonably good correlation, the hematology instrument showed a distinct tendency to overestimate PLT counts at low levels. CONCLUSION: It is proposed that this standardized immunoplatelet method offers the best approach in evaluating, at the clinical level, the possibility of lower PLT transfusion triggers. It can be used to evaluate the performance limitations of automated hematology analyzers that are widely used at the present time.

Adolescent↗

PubMed2006

Validation of a simple HPLC method for DRF-4848, a novel COX-2 inhibitor suitable for pharmacokinetic application in rats.

For pharmacokinetic and toxicokinetic purpose a simple HPLC-UV method has been developed and validated for the estimation of DRF-4848, a novel COX-2 inhibitor in rat plasma. A liquid-liquid extraction was used to extract DRF-4848 and internal standard (IS, DRF-4367) from rat plasma. The analysis was performed on a C(18) column with UV detection at 285 nm. The isocratic mobile phase, 0.01 M potassium dihydrogen ortho phosphate (pH 3.2) and acetonitrile (50:50, v/v) was run at a flow rate of 1 mL/min. The retention times of DRF-4848 and IS were 6.8 and 11.2 min, respectively. Absolute recovery for analyte and IS was >80% from rat plasma. A linear response was observed over a concentration range 0.1-20 microg/mL. The lower limit of quantification (LLOQ) of DRF-4848 was 0.1 microg/mL. The inter- and intra-day precisions in the measurement of quality control (QC) samples, 0.1, 0.3, 8.0 and 15.0 microg/mL, were in the range 1.74-8.70% relative standard deviation (RSD) and 0.75-8.43% RSD, respectively. Accuracy in the measurement of QC samples was in the range 93.29-116.51% of the nominal values. Analyte and IS were stable in the battery of stability studies viz., benchtop, autosampler, long-term and freeze/thaw cycles.

4-Butyrolactone↗

PubMed1977

Liquid chromatography in pharmaceutical analysis VIII: determination of isoniazid and acetyl derivative in plasma and urine samples.

Parameters are described for the qualitative and quantitative analysis of a mixture of isoniazid and its acetyl derivative. The compounds are chromatographed on an octadecylsilane column, using absolute methanol-distilled water (60:40) at pH 2.5 containing 0.01 M dioctyl sodium sulfosuccinate. The flow rate was 2.0 ml/min (2500 psig). The separation and quantification are applicable to plasma and urine samples. The determination in each biological fluid can be achieved in approximately 90 min with percentage accuracies for isoniazid of 5.25 and 7.45 and for the acetyl derivative of 4.47 and 1.56 in plasma and urine, respectively.

Acetylation↗

PubMed1992

Morphometry versus densitometry--a comparison by use of casts of human coronary arteries.

Geometric and densitometric methods for quantitative coronary arteriography have generally been compared by use of phantoms simulating arteries with circular lumina ('Hole phantoms'). We have used more adequate phantoms obtained by casting disease-free and atheromatous human coronary arteries. The phantoms, filled with contrast medium, were imaged digitally (1024 x 1024 x 10 matrix) under experimental conditions simulating routine coronary angiography. The angiographic 'diameters' and the densitometric cross-sectional areas of 59 marked lumina were determined in single plane and orthogonal biplane raw images. Geometric calibration was performed by help of a 7F coronary catheter. For the densitometric calibration, we used a 'hole phantom' attached to the image intensifier. The obtained luminal areas were compared to their true values determined previously by planimetry. The mean absolute error of single plane cross-sections obtained geometrically was 1.53 mm2. Biplane imaging reduced it by a factor 2.4 to 0.64 mm2. The corresponding mean absolute errors for densitometry were 0.56 mm2 and 0.51 mm2. Single plane 'diameter' measurements appear thus of very limited value for hemodynamic conclusions. In contrast, biplane geometric quantification was not markedly inferior to single plane and biplane densitometry.

Absorptiometry, Photon↗

PubMed1994

Tissular expression and regulation of type 1 angiotensin II receptor subtypes by quantitative reverse transcriptase-polymerase chain reaction analysis.

Recent studies have revealed that angiotensin II (Ang II) interacts with two pharmacologically different types of seven-transmembrane domain receptors, hence named Ang II type 1 and type 2 (AT1 and AT2) receptors. cDNAs for the AT1 receptor have been cloned, and the existence of two receptor subtypes, AT1A and AT1B, has been revealed in rat and mouse. This study presents a new approach for the specific quantification of AT1A and AT1B receptor mRNAs by reverse transcription and polymerase chain reaction amplification in the presence of an AT1 receptor mutant cRNA as internal standard. Absolute quantities of mRNA are then determined by extrapolation using the standard curve generated with the internal standard. Moreover, addition of this internal standard to each tube controls for both reverse transcription and polymerase chain reaction amplification in each sample. In male Wistar rats, the highest absolute AT1A receptor mRNA levels were found in liver and kidney and those for AT1B receptor mRNA in the pituitary. Expressed as a percentage of total AT1A+AT1B receptor mRNA content, AT1A receptor mRNA content was 100% in liver, 85% in lung, 73% in kidney, 65% in aorta, 48% in adrenals, and 15% in the hypophysis. Since this approach can determine absolute AT1A and AT1B receptor mRNA quantities in different organs, it allows the study of the regulation of their expression under different pathophysiological conditions. After sodium depletion, known to induce hyperactivity of the renin-angiotensin system, adrenal AT1A and AT1B receptor mRNA levels were increased by 60% and 110%, respectively. In contrast, in renovascular hypertension (two-kidney, one clip), also associated with elevated circulating plasma renin activity, adrenal AT1B receptor mRNA levels decreased by 50%, whereas there was no change in those of AT1A. Therefore, the differential distribution and regulation of these two receptor subtypes suggest that each of them might be involved in the mediation of different biological effects of Ang II.

Adrenal Glands↗

PubMedDate not supplied

The representation of uncertainty in medical expert systems.

The development of the rule-based expert system has provided important new techniques for the representation of knowledge. However, continued use of this representational scheme has highlighted some of its deficiencies. In particular, many within scientific and non-scientific fields attempting to use the rule-base design to describe natural phenomena often find it difficult to represent the complexities of the world as 'absolute' rules. For this reason, many investigators acknowledge the need to add an uncertainty mechanism to the rule-base construct. Such a facility would allow the quantification of accuracy or strength of association within individual rules Although agreement exists on the need for an uncertainty representation facility, the debate concerning the most appropriate methodology is far from resolved. The purpose of this paper is to provide a review and commentary on the current state of debate over the five most popular candidate uncertainty models: symbolic representation, MYCIN certainty factors, Bayesian, Dempster-Shafer and fuzzy set logic. The advantages and disadvantages of each uncertainty calculi will be presented and assessed with respect to their applicability to the medical expert systems domain.

Bayes Theorem↗

PubMedDate not supplied

A reversed-phase high-performance liquid chromatographic method for the determination of zafirlukast in pharmaceutical formulations and human plasma.

Zafirlukast (ZAF) is a leukotriene receptor antagonist used in the treatment of chronic asthma. In this study, a simple and sensitive reversed-phase, high-performance liquid chromatographic method was developed for the determination of ZAF in pharmaceutical formulations and human plasma. Piribedil was used as an internal standard. Analysis was carried out on a Nucleosil C18 100 A (150 mm x 4.6 mm id, 5 Vm) column with acetonitrile-pH 3.0 acetate buffer (70 + 30, v/v) as the mobile phase at a flow rate of 0.8 mL/min. The peak was detected by an ultraviolet detector set at a wavelength of 240 nm. The retention times were about 3.9 min for piribedil and 5.8 min for ZAF. The developed method was applied to the determination of ZAF in its pharmaceutical formulation and spiked human plasma. For quantification of ZAF in spiked plasma, proteins were precipitated with ethanol before chromatographic analysis. The calibration range was linear from 49.69-437.50 ng/mL in spiked plasma. The absolute recovery from spiked plasma was 98.73 +/- 0.42% at a concentration of 254.78 ng/mL of ZAF. No endogenous substances from plasma were found to interfere.

Anti-Asthmatic Agents↗

PubMed2006

Continuous ASL perfusion fMRI investigation of higher cognition: quantification of tonic CBF changes during sustained attention and working memory tasks.

Arterial spin labeling (ASL) perfusion fMRI is an emerging method in clinical neuroimaging. Its non-invasiveness, absence of low frequency noise, and ability to quantify the absolute level of cerebral blood flow (CBF) make the method ideal for longitudinal designs or low frequency paradigms. Despite the usefulness in the study of cognitive dysfunctions in clinical populations, perfusion activation studies to date have been conducted for simple sensorimotor paradigms or with single-slice acquisition, mainly due to technical challenges. Using our recently developed amplitude-modulated continuous ASL (CASL) perfusion fMRI protocol, we assessed the feasibility of a higher level cognitive activation study in twelve healthy subjects. Taking advantage of the ASL noise properties, we were able to study tonic CBF changes during uninterrupted 6-min continuous performance of working memory and sustained attention tasks. For the visual sustained attention task, regional CBF increases (6-12 ml/100 g/min) were detected in the right middle frontal gyrus, the bilateral occipital gyri, and the anterior cingulate/medial frontal gyri. During the 2-back working memory task, significantly increased activations (7-11 ml/100 g/min) were found in the left inferior frontal/precentral gyri, the left inferior parietal lobule, the anterior cingulate/medial frontal gyri, and the left occipital gyrus. Locations of activated and deactivated areas largely concur with previous PET and BOLD fMRI studies utilizing similar paradigms. These results demonstrate that CASL perfusion fMRI can be successfully utilized for the investigation of the tonic CBF changes associated with high level cognitive operations. Increased applications of the method to the investigation of cognitively impaired populations are expected to follow.

Adult↗

PubMed2002

Reproducibility of standardized retroillumination photography for quantification of posterior capsule opacification.

PURPOSE: To determine the short-term reproducibility of standardized digital retroillumination images of regeneratory posterior capsule opacification (PCO) using the photographic setup at 1 institution. SETTING: Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: In this prospective study, 60 retroillumination images of 30 eyes with varying degrees of PCO and different types of intraocular lenses were acquired with a standardized digital coaxial retroillumination system. Two images were taken per eye with a 1-minute interval between images. Ten other eyes were photographed in the same way but with a 5-day interval between the 2 images. All images were evaluated with a fully automated, objective PCO analysis software in which the PCO score was from 0 to 100. The 2 results (A, B) in each eye were compared, and the differences were calculated. RESULTS: There was a high correlation between the A and B results (r = 0.99). The mean absolute difference was 3.7%. The repeatability coefficient was 8.8%. CONCLUSION: Digital coaxial retroillumination photography provided quick acquisition of regeneratory PCO images. It provided excellent image quality and high reproducibility. The technique forms a good basis for automated quantification of PCO with new software systems.

Cataract↗

PubMed2006

Sensitive and rapid liquid chromatography/tandem mass spectrometry assay for the quantification of amlodipine in human plasma.

A simple, sensitive and rapid high-performance liquid chromatography/electrospray ionization tandem mass spectrometry method was developed and validated for the assay of amlodipine in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase C(18) column and analyzed by MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 409/238 for amlodipine and m/z 409/228 for the IS. The assay exhibited a linear dynamic range of 50-10,000 pg/mL for amlodipine in human plasma. The lower limit of quantification was 50 pg/mL with a relative standard deviation of less than 8%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The average absolute recoveries of amlodipine and the IS from spiked plasma samples were 74.7 +/- 4.6 and 72.1 +/- 2.0%, respectively. A run time of 1.5 min for each sample made it possible to analyze more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies. The observed maximum plasma concentration (Cmax) of amlodipine (2.5 mg oral dose) was 1425 pg/mL, time to observed maximum plasma concentration (Tmax) was 8.1 h and elimination half-life (T(1/2)) was 50.1 h.

Adolescent↗

PubMed2006

Simultaneous quantification of atorvastatin and active metabolites in human plasma by liquid chromatography-tandem mass spectrometry using rosuvastatin as internal standard.

A simple, sensitive, selective and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of atorvastatin and its active metabolites ortho-hydroxyatorvastatin and para-hydroxyatorvastatin in human plasma using rosuvastatin as internal standard (IS). Following simple liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase C18 column and analyzed by MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 559/440 for atorvastatin, m/z 575/466 for ortho-hydroxyatorvastatin, m/z 575/440 for para-hydroxyatorvastatin and m/z 482/258 for the IS. The assay exhibited a linear dynamic range of 0.1-20 ng/mL for atorvastatin and its two metabolites in human plasma. The lower limit of quantification was 100 pg/mL with a relative standard deviation of less than 8%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The average absolute recoveries of atorvastatin, ortho-hydroxyatorvastatin, para-hydroxyatorvastatin and the IS from spiked plasma samples were 54.2 +/- 3.2, 50.1 +/- 3.8, 65.2 +/- 3.6 and 71.7 +/- 2.7%, respectively. A run time of 2.5 min for each sample made it possible to analyze more than 300 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Atorvastatin↗

PubMed2005

Liquid chromatography/electrospray ionization mass spectrometry method for the quantification of valproic acid in human plasma.

A simple, sensitive and rapid liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) method was developed and validated for the quantification of valproic acid, an antiepileptic drug, in human plasma using benzoic acid as internal standard (IS). Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase C18 column and analyzed by MS in the single ion monitoring mode using the respective [M-H]- ions, m/z 143 for valproic acid and m/z 121 for the IS. The assay exhibited a linear dynamic range of 0.5-60 microg/mL for valproic acid in human plasma. The lower limit of quantification was 500 ng/mL with a relative standard deviation of less than 10%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The average absolute recoveries of valproic acid and the IS from spiked plasma samples were 96.1+/-4.2 and 95.6+/-2.7%, respectively. A run time of 4.5 min for each sample made it possible to analyze more than 250 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability and bioequivalence studies.

Anticonvulsants↗

PubMed1981

Practical applications of the microphotometric quantification of histoenzyme reactions.

There are many histochemical reactions which can be used for the accurate topographic detection of enzymes in tissues. There are also many reports of applications of these techniques in which the results have been evaluated subjectively. However, only a few of these methods have been the subject of quantification, using different methodologies, most of them based on microphotometry. A critical analysis of these procedures has generally shown that they are valid either relatively or at an absolute level. Nevertheless, the routine application of these methods is not as widespread as one might expect. In this paper, the methodological developments that have taken place in the histochemical assay of some enzymes by microspectrophotometry are reviewed briefly. The enzymes include acid phosphatase, non-specific esterase, succinate dehydrogenase and cytochrome oxidase. These methods have given consistent and useful results when applied to our experimental models of irradiated skin, and thus seem useful for various other applications. The reasons why there have been so few applications for quantitative histochemistry are also discussed together with possible ways of making its use more general.

Acid Phosphatase↗