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At least 415 records · Page 23Linked to original sources

PubMed2026

Telomere length in patients with non-functional adrenal incidentalomas.

Telomeres maintain genomic integrity during cell replication by preventing chromosomal fusions. Beside genetic influences, telomere length is affected by environmental factors such as oxidative stress and inflammation. These mechanisms also contribute to metabolic syndrome components linked to cellular aging. We aim to evaluate whether telomere length is shortened in patients with non-functional adrenal incidentaloma (NFAI) compared to the control group. This study was designed as a prospective, single-center study. The total of 88 participants included were 44 patients aged between 40 and 60 years with NFAI in our endocrinology clinic and 44 control subjects. An Absolute Human Telomere Lengths Quantification qPCR Assay kit (Nucleotestbio, Budapest, Hungary) was used for analyses. There was no significant difference between the NFAI and control groups regarding age and sex distribution. Telomere length was significantly shorter in the NFAI group (NFAI group: 3.680 ± 1.970 kb; control group: 4.469 ± 1.672 kb; p = 0.046). While no significant difference was found in telomere lengths in subgroup analyses, patients with basal adrenocorticotropic hormone (ACTH) levels <15 pg/mL had significantly shorter telomeres than those with basal ACTH levels ≥15 pg/mL (p = 0.034). A strong positive correlation was observed only between telomere length and ACTH level (p = 0.001). This study demonstrated that telomere length is significantly shortened in NFAI patients. Here, we propose that the underlying cause of telomere length shortening in the NFAI group may be related to increased cardiovascular risk and an elevated inflammatory state, even in the presence of cortisol levels within the normal range.

Humans↗

PubMed2005

Developments in nuclear cardiology: transition from single photon emission computed tomography to positron emission tomography-computed tomography.

Recent advances in positron emission tomography (PET) instrumentation have paralleled those of multichannel computed tomography (CT) for cardiac applications. Whereas multichannel CT angiography provides information on the presence and extent of anatomical luminal narrowing of epicardial coronary arteries, stress myocardial perfusion PET provides information on the downstream functional consequences of such anatomic lesions. With the advent of hybrid PET/CT systems, such complementary information of anatomy and physiology can be realized immediately at the same imaging session. By acquiring dynamic, gated myocardial perfusion data, PET studies provide insight into impairment of regional coronary blood flow reserve and microvascular endothelial dysfunction. This paper presents recent developments in PET detector materials, acquisition modes, combined PET/CT scanners, rubidium-82 (Rb-82) gated myocardial perfusion studies and analysis methods for absolute myocardial blood flow quantification.

Coronary Disease↗

PubMed1993

Absolute concentrations of metabolites in the adult human brain in vivo: quantification of localized proton MR spectra.

In vivo concentrations of cerebral metabolites were obtained by means of 52 single-voxel, localized proton magnetic resonance (MR) spectroscopic examinations of different regions of the brain performed in 26 healthy adults aged 21-32 years. The study was performed at 2.0 T with use of a circularly polarized head coil to ensure homogeneous radio-frequency excitation and signal reception. Proton MR spectra were obtained in the stimulated-echo acquisition mode under fully relaxed conditions (repetition time > or = 6,000 msec) and at short echo times (20 msec) to minimize corrections due to T1 and T2 attenuation and depict the spectra of metabolites with strongly coupled resonances. Absolute concentrations were obtained by means of calibration of resonance signal areas with those of pertinent metabolite solutions from separate studies and correction for coil loading and partial volume effects (eg, with perfused capillary networks and cerebrospinal fluid). The results provide a quantitative basis for studies of both normal human neurochemistry in vivo and metabolic alterations in diseases of the brain.

Adult↗

PubMedDate not supplied

An improved NMR method for the quantification of alpha-acids in hops and hop products.

A new and independent method for the quantification of alpha-acids in hops and hop products has been developed. NMR was used as a qualitative method for the complete assignment of all 1H- and 13C-NMR signals of the three main alpha-acids, cohumulone (1), humulone (2) and adhumulone (3). In a 13C two-dimensional INADEQUATE experiment, the 13C-NMR spectrum of 1 was unambiguously assigned via the carbon-carbon connectivities. Use of NMR as a quantitative method allowed quantification of the pure and individual alpha-acids 1 and 2, and the determination of the absolute concentration of solutions of these compounds. Quantification of alpha-acids by NMR is less complicated and more reliable than the methods used until now.

Cyclohexanones↗

PubMed2005

Input parameter sensitivity analysis and comparison of quantification models for continuous arterial spin labeling.

The regional cerebral blood flow (rCBF) values determined using continuous arterial spin labeling (CASL) are subject to several sources of variability, including natural physiologic variations, sensitivity to the input parameters, and the use of different quantification models. To date, a thorough analysis of the impact of input parameters and the choice of quantification model has not been performed. These sources of variability were investigated through computer simulations using bootstrap techniques on actual CASL data. Coefficients of variation for representative single voxels were 6.7% for gray matter and 29% for white matter, and for eight-voxel regions of interest they were 4.5% for gray matter and 23% for white matter. Comparison of nine CASL quantification models showed differences in gray matter rCBF values of up to 42%. An analysis of the sensitivity of the rCBF to input parameters for each of the nine quantification models demonstrated that accurate quantification of the inversion efficiency, tissue and arterial blood longitudinal relaxation times, and transit times were critical in calculating precise rCBF values. The large potential variations in rCBF and the effect of the choice of quantification model suggest that interpreting absolute rCBF values in CASL studies can be challenging and requires great care.

Adult↗

PubMed2004

Styrene oxide DNA adducts: quantitative determination using 31P monitoring.

The reaction of styrene oxide, a potential carcinogen in humans, with DNA constituents has been used to develop an improved method for quantification of DNA adducts. To enable monitoring of DNA adducts caused by xenobiotics at physiological relevant levels, a robust, reliable and powerful method based on monitoring of phosphorus in nucleotides is described. An efficient enzymatic digestion step and a sample-preconcentration procedure are essential, and enable separation of alkylated nucleotides from the large excess of native nucleotides. The adducts are detected by means of the phosphorus signal measured at mass m/z = 31 with an inductively-coupled-plasma mass spectrometer. Bis(4-nitrophenyl)phosphate (BNPP) serves as internal standard for quantification of the adducts. The absolute limit of detection, 45 fmol, corresponds to detection of three modified nucleotides among 10(7) native nucleotides (the calculation is based on use of 50 microg calf thymus DNA). An adduct formation ratio at the DNA of 3.6 adducts per 1000 nucleotides was measured, which is 75% lower than for reaction with monomeric 2'-deoxy-nucleotides. In addition, a substantial amount of phosphate adducts were detected, but in DNA the rate of phosphate formation was lower than with monomeric nucleotides. Most probably these adducts escaped unnoticed when 31P-post-labelling was employed.

DNA Adducts↗

PubMed2004

Expression of the proliferating cell nuclear antigen and protein products of tumour suppressor genes in the human foetal testis.

Tumour suppressor genes retinoblastoma (Rb1) and adenomatous polyposis coli (Apc) as well as the proliferating cell nuclear antigen (PCNA) are involved in embryonic development. The purpose of the present study was to investigate the expression of Rb1 protein, APC protein and PCNA during development of the human foetal testis. Qualitative analysis of their expression at the single-cell level was performed using immunohistochemistry on archive samples of the foetal testis (18-37 gestation week). Stereological parameters (volume density, absolute volume, numerical density, absolute number) were calculated for quantification of the overall expression of those proteins that were expressed frequently enough for such an analysis. PCNA was frequently expressed in nuclei of immature Sertoli cells and prospermatogonia and less frequently in surrounding peritubular (myoid) and interstitial cells. The pRb1 protein was present in nuclei of prospermatogonia and Sertoli cells but was absent from the interstitial tissue. APC protein was expressed in the cytoplasm of a very small number of prospermatogonia and interstitial (Leydig) cells. The overall expression of PCNA in all stages of development was higher than pRb1 expression.

Adenomatous Polyposis Coli Protein↗

PubMed2004

N-acetylaspartate: a literature review of animal research on brain ischaemia.

The present review examines and discusses the changes in N-acetylaspartate (NAA) concentration in the ischaemic brain from the existing literature of animal research. By summarizing the current knowledge on NAA metabolic pathways and reviewing the data obtained in animal models of global and focal ischaemia, the following conclusions emerge from this compilation: (i) both magnetic resonance spectroscopy (MRS) and the absolute HPLC method of NAA quantification give converging information; (ii) decreases in brain NAA concentration in acute stroke can be considered as an index of neuronal loss or dysfunction, although NAA redistribution by glial cells and NAA trapping in cell debris restrict its use as a quantitative neuronal marker; (iii) further studies on NAA metabolism in pathologic brain are required before using NAA measurement in the chronic stage of ischaemia for evaluating neuroprotective strategies.

Animals↗

PubMed1994

A new method of quantification of the pulmonary regional distribution of aerosols using combined CT and SPECT and its application to nedocromil sodium administered by metered dose inhaler.

Aerosols of nedocromil sodium labelled with 99Tcm were delivered on 20 separate occasions to healthy male volunteers. Planar and single photon emission computerized tomography (SPECT) gamma scintigraphy were immediately performed to assess the pulmonary regional distribution of delivered aerosol. On a separate occasion volunteers were imaged using X-ray computed tomography (CT). Alignment of SPECT and CT images was performed using marked anatomical features and the anterior and lateral skin outlines. CT images provided data for attenuation correction and were used to define the anatomical lung volume. Central to peripheral (CP) ratios of deposited activity were calculated from volumes of interest in coronal and transverse sections of the right lung. These were compared with CP ratios obtained from planar images obtained immediately following aerosol inhalation. Volumetric CP ratio correlated significantly with immediate planar CP ratio (p < 0.001). Analysis of deposition in the whole right lung was performed by separating the SPECT lung data into a series of thin concentric shells centred on the entry of the right main bronchus. Measures were defined for describing the variation of deposition density and cumulative total deposition with distance from the lung centre. These showed significant correlation with planar CP ratio (p < 0.001). SPECT analysis using CT is consistent with planar measures of aerosol deposition but offers a more complete quantification of aerosol penetration and absolute deposited activity within the whole lung. It is a valuable new tool for aerosol analysis.

Administration, Inhalation↗

PubMed2001

Use of wavelet transforms in analysis of time-activity data from cardiac PET.

UNLABELLED: Because of its intrinsic quantitative properties, PET permits measurement of myocardial perfusion and metabolism in absolute terms (i.e., mL/g/min). However, quantification has been limited by errors produced in image acquisition, selection of regions of interest, and data analysis. The goal of this study was to evaluate a newly developed, novel, wavelet-based noise-reduction approach that can objectively extract biologic signals hidden within dynamic PET data. METHODS: Quantification of myocardial perfusion using dynamic PET imaging with 82Rb, H2(15)O, and 13NH3 was selected to evaluate the effects of the wavelet-based noise-reduction protocol. Dynamic PET data were fitted to appropriate mathematic models before and after wavelet-based noise reduction to get flow estimates. Time-activity curves, precision, accuracy, and differentiating capacity derived from the wavelet protocol were compared with those obtained from unmodified data processing. A total of 84 human studies was analyzed, including 43 at rest (18 82Rb scans, 18 H2(15)O scans, and 7 13NH3 scans) and 41 after coronary hyperemia with dipyridamole (17 82Rb scans, 17 H2(15)O scans, and 7 13NH3 scans). RESULTS: For every tracer tested under all conditions, the wavelet method improved the shape of blood and tissue time-activity curves, increased estimate-to-error ratios, and maintained fidelity of flow in regions as small as 0.85 cm3. It also improved the accuracy of flow estimates derived from 82Rb to the level of that achieved with H2(15)O, which was not affected markedly by the wavelet process. In studies of patients with coronary disease, regional heterogeneity of myocardial perfusion was preserved and flow estimates in infarcted regions were differentiated more easily from normal regions. CONCLUSION: The wavelet-based noise-reduction method effectively and objectively extracted tracer time-activity curves from data with low signal-to-noise ratios and improved the accuracy and precision of measurements with all tracer techniques studied. The approach should be generalizable to other image modalities such as functional MRI and CT and, therefore, improve the ability to quantify dynamic physiologic processes.

Coronary Circulation↗

PubMed2002

Validated HPLC method for the determination of tinidazole in human serum and its application in a clinical pharmacokinetic study.

A high performance liquid chromatographic (HPLC) method for the determination of tinidazole in human serum using metronidazole as internal standard (IS) is described. Protein precipitation is used for the preparation of sample. Mobile phase consisting of 0.002 M phosphate buffer, methanol and acetonitrile mixture (85:7.5:7.5/v/v/v) was used at a flow rate of 1 ml/min on a C18 column. The eluate was monitored using an UV/Vis detector set at 320 nm. Ratio of peak area of analyte to IS was used for quantification of serum samples. The absolute recovery was greater than 95% over a concentration range of 0.5 to 30 micrograms/ml and the limit of quantitation was 0.05 microgram/ml. The intra-day relative standard deviation (RSD) measured at 0.5, 5, 15 and 30 micrograms/ml ranged from 0.36 to 6.14%. The inter-day RSD ranged from 1.14 to 4.21%. The method is simple, sensitive and has been successfully used in a pharmacokinetic study conducted in healthy human volunteers.

Antitrichomonal Agents↗

PubMed2002

Validated HPLC method for determination of chlorzoxazone in human serum and its application in a clinical pharmacokinetic study.

A high performance liquid chromatographic (HPLC) method for the determination of chloroxazone in human serum using phenacetin as internal standard (IS) is described. Protein precipitation is used for preparation of the sample. A mobile phase consisting of acetonitrile and 0.5% acetic acid in water mixture (40:60 v/v) was used at a flow rate of 1 ml/min on a C18 column. The eluate was monitored using an UV/VIS detector set at 287 nm. Ratio of peak area of analyte to IS was used for quantification of serum samples. The absolute recovery was greater than 96% over a concentration range of 1 to 100 micrograms/ml and the limit of quantitation was 0.05 microgram/ml. The intra-day relative standard deviation (RSD) measured at 1, 10, 50, and 100 micrograms/ml ranged from 0.9 to 5.1%. The inter-day RSD ranged from 0.6 to 3.0%. The method is simple, sensitive and has been successfully used in pharmacokinetic study conducted in healthy human volunteers.

Adult↗

PubMed1995

[Value of various suture materials for defect reconstruction of peripheral nerves].

A total of 40 surgical procedures were performed for bridging defects of the peronaeus nerve in 20 experimental animals (White Russian rabbits) with absorbable and non-absorbable suture materials. To investigate whether differences in the biological behaviour of suture materials may influence the formation of axons in the coaptation areas positively or negatively, the nerves were examined histologically and electrophysiologically and the regeneration process in the m. tibialis anterior, the reacting organ of the n. peronaeus, was assessed by histomorphometric quantification. Despite minor deviations in absolute values, significance tests and statistical evaluation with Wilcoxon's test revealed no significant differences among the groups. We could show that differences in biological behaviour of absorbable and non-absorbable suture materials are without influence on nerve regeneration in the proximal and distal coaptation areas and therefore without effect on the final results of nerve regeneration in defect areas.

Animals↗

PubMed1997

Quantitative polymerase chain reaction for human herpesvirus diagnosis and measurement of Epstein-Barr virus burden in posttransplant lymphoproliferative disorder.

Human herpesviruses can cause acute diseases such as chicken pox or mononucleosis, but also may reactivate during immunosuppression and result in severe or life-threatening illnesses such as shingles or lymphoproliferative disorders. We report the development and validation of a quantitative PCR method to measure viral burden for all eight human herpesviruses (HSV1, HSV2, VZV, EBV, CMV, HHV6, HHV7, and KSHV) in patients' samples. The method uses an internal standard that is coamplified with the viral target, allowing quantification of viral genomes in absolute terms (e.g., viral targets/mL of blood) and ruling out false-negative results. We demonstrate that transplant patients with lymphoproliferative disorder carry an EBV viral burden 3 logs higher than nontransplant patients. EBV titers in transplant patients without a lymphoproliferative disorder are between these values. This quantitative PCR method may aid in differentiating clinically significant vs latent viral burden in immunosuppressed patients.

Herpesviridae Infections↗

PubMed2000

Validated HPLC method for determination of PAT-5A, an insulin sensitizing agent, in rat plasma.

A high performance liquid chromatographic method for the determination of PAT-5A (a potent insulin sensitizer) using DRF-2095 (a thiazolidinedione) as internal standard (I.S.) is described. A 1:1 v/v ethylacetate and dichloromethane solvent mixture was used for extraction of PAT-5A from plasma. A Kromasil KR100-5C18-250A, 5 microm, 4.6 x 250 mm SS column was used for the analysis. Mobile phase consisting of sodium dihydrogen phosphate (pH 4.0, 0.05 M) and methanol mixture (25:75, v/v) was used at a flow rate of 1.0 ml/min. The eluate was monitored using a UV detector set at 345 nm. Ratio of peak area of analyte to I.S. was used for quantification of plasma samples. Using this method the absolute recovery of PAT-5A from rat plasma was > 90% and the limit of quantification was 0.05 microg/ml. The intra-day relative standard deviation (RSD) ranged from 2.19 to 4.98% at 1.0 microg/ml, 1.05 to 3.68% at 10.0 microg/ml and 3.14 to 5.08% at 50 microg/ml. The inter-day RSD were 1.6, 2.24 and 1.54% at 1, 10 and 50 microg/ml, respectively. The method was applied to measure the plasma concentrations of PAT-5A in pharmacokinetic and bioavailability studies in male Wistar rats.

Animals↗

PubMed2002

Cerebral hemoglobin concentration and oxygen saturation measured by intensity modulated optical spectroscopy in the human fetus during labor.

AIMS: To quantify hemoglobin concentration and oxygen saturation in the human fetal brain using intensity modulated optical spectroscopy during labor. METHODS: A specially designed probe was applied to the fetal scalp in 20 women during uncomplicated labor at term. Optical fibres transmitted near infra-red light to and from an intensity modulated optical spectrometer (IMOS), which detected changes in the optical parameters of the infra-red light source. Using novel off-line analytic techniques, these changes were converted into absolute measurements of oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb). Summing Hb and HbO2 gives total hemoglobin concentration (HbT) and HbO2/HbT x 100% provided measurements of cerebral saturation (SmcO2). RESULTS: Of 20 fetuses studied, data from 10 fetuses were suitable for analysis. Over three consecutive uterine contractions, the mean (+/- SD) absolute cerebral concentrations of Hb and HbO2 were 30 +/- 18 and 46 +/- 21 mumol/l, respectively. This gave a mean cerebral HbT of 77 +/- 29 mumol/l and a mean SmcO2 of 59 +/- 12%. In the other ten fetuses insufficient light was detected to allow chromophore quantification. CONCLUSION: These are the first absolute measurements of cerebral Hb and HbO2 in human fetuses during labor. The values of total hemoglobin are similar to those obtained in neonates with hypoxia-ischemia and the measurements of fetal cerebral oxygen saturation are similar to previously published values.

Female↗

PubMed2004

Rapid determination of the active leflunomide metabolite A77 1726 in human plasma by high-performance liquid chromatography.

A simple method for the measurement of the active leflunomide metabolite A77 1726 in human plasma by HPLC is presented. The sample workup was simple, using acetonitrile for protein precipitation. Chromatographic separation of A77 1726 and the internal standard, alpha-phenylcinnamic acid, was achieved using a C(18) column with UV detection at 305 nm. The assay displayed reproducible linearity for A77 1726 with determination coefficients (r2) > 0.997 over the concentration range 0.5-60.0 microg/ml. The reproducibility (%CV) for intra- and inter-day assays of spiked controls was <5%. The limit of quantification was 0.8 microg/ml. The average absolute recovery was approximately 100%. This assay is suitable for the determination of A77 1726 in plasma of patients taking leflunomide, and is simpler to use than other HPLC methods reported previously.

Adjuvants, Immunologic↗

PubMed2004

Determination of the new HIV-protease inhibitor atazanavir by liquid chromatography after solid-phase extraction.

An HPLC method previously described for the simultaneous assay of amprenavir, ritonavir, indinavir, saquinavir, nelfinavir and efavirenz is proposed here for the simultaneous analysis of the new HIV protease inhibitor atazanavir (ATV) in human plasma, by off-line solid-phase extraction (SPE) followed by HPLC coupled with UV-diode array detection. After viral inactivation by heat (60 degrees C for 60 min), plasma (600 microl) with clozapine (internal standard) is diluted 1 + 1 with phosphate buffer pH 7 and subjected to a SPE on a C18 cartridge. Matrix components are eliminated with 2 x 500 microl of a solution of 0.1% H(3)PO(4) neutralised with NaOH to pH 7. ATV is eluted with 3 x 500 microl MeOH. The resulting eluate is evaporated under nitrogen at room temperature and is reconstituted in 100 microl MeOH/H(2)O 50/50. A 40 microl volume is injected onto a Nucleosil 100-5 microm C18 AB column. ATV is analysed by UV detection at 201 nm using a gradient elution program with solvents constituted of MeCN and phosphate buffer adjusted to pH 5.14. The mobile phase also contains 0.02% sodium heptanesulfonate, enabling an excellent separation of ATV from the other HIV protease inhibitors (PIs) amprenavir, indinavir, saquinavir, ritonavir, lopinavir, nelfinavir and the non-nucleoside reverse transcriptase inhibitors (NNRTIs) efavirenz and nevirapine. The calibration curves are linear up to 10 microg/ml, with a lower limit of quantification of 0.2 microg/ml. The mean absolute recovery of ATV is 96.4 +/- 3.2%. The method is precise with mean inter-day CVs within 1.1-6.1%, and accurate (range of inter-day deviations +0.3 to +2.3%). The method has been validated and is currently applied to the monitoring of ATV in HIV patients.

Atazanavir Sulfate↗