High-speed detection of the two common alpha(1)-antitrypsin deficiency alleles Pi*Z and Pi*S by real-time fluorescence PCR and melting curves.
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Alleles↗
Biomedical subjects
G Schmitz
Publications and source records attributed to G Schmitz.
Nitrous oxide impairs the signaling of neutrophils downstream of receptors.
(1) Nitrous oxide has been shown to impair the oxidative function of neutrophils. (2) To characterize the type and the site of the drug interaction, receptor expression, cytosolic-free calcium, and H2O2 production of neutrophils were assessed using flow cytometry. (3) Nitrous oxide depresses receptor-dependent generation of H2O2 in a concentration-dependent manner. The response upon direct activation of protein kinase C (PKC) was unaffected. (4) No interference was found at the receptor sites, the linked G proteins, and the subsequent release of Ca2+, indicating a localization of the nitrous oxide interaction downstream of receptors and G proteins at or near to PKC.
Anesthetics, Inhalation↗
Proof of hepatitis A virus negative-sense RNA by RNA/DNA-hybrid detection: a method for specific detection of both viral negative- and positive-strand RNA species.
The detection of hepatitis A virus (HAV) negative-strand RNA, which is synthesized during replication of the positive-strand RNA genome, proved to be difficult. We developed a method for the specific detection of HAV negative-strand RNA by RNA-DNA hybridization and luminescence detection using an anti-RNA:DNA hybrid antibody. This method, which is also applicable for the specific detection of positive-strand RNA, offers a simple, yet relatively rapid and certain means of detecting low amounts of RNA such as HAV negative-strand RNA. By using appropriate hybridization DNA probes, the method should be applicable for the detection of single-stranded RNA species of different viruses in general.
Animals↗
Whole blood analysis of reticulated platelets: improvements of detection and assay stability.
The flow cytometric analysis of reticulated platelets based on the fluorescent derivatization of their RNA content is increasingly used for the diagnostic classification of patients with thrombocytopenia as well as the monitoring of thrombopoiesis recovering under therapy. Many different modifications of the analytical protocol have been published following the first description in 1990 but consensus on the method has not yet been established. We have now reevaluated the assay's methodology in order to optimize sensitivity and specificity and reduce the time length of incubation and washing procedures. In the modified experimental approach native whole blood is incubated for 15 min with an increased amount of thiazole orange (1 microg/ml) in the presence of phycoerythrin labeled antibodies directed against the constitutively surface expressed antigen GPlb. Data acquisition on the flow cytometer can be started immediately after stopping and stabilization of the reaction by paraformaldehyde fixation. Thiazole orange fluorescence was not significantly changed in thrombin-activated, degranulated platelets compared to resting platelets indicating no significant non-specific staining of platelet granules under the selected test conditions. In addition, experiments employing RNAse digestion demonstrated specificity of thiazole orange staining for platelet RNA.
Blood Cell Count↗
Flow cytometric quantitation of immunofluorescence intensity: problems and perspectives. European Working Group on Clinical Cell Analysis.
Quantitation of immunofluorescence intensity serves to estimate the number of defined molecules expressed on or in cells. Clinical applications of this diagnostic tool are increasing, e.g., aberrant expression of various antigens (Ag) by leukemic blasts or lymphoma cells, intensity of CD38 expression by CD8+ T-lymphocytes to monitor activation status, and intensity of CD62P to detect platelet activation. In this report we discuss the quality-control measures required for quantitation of fluorescence intensity, and we review seven concepts that have been developed to quantify fluorescence intensity during the past 15 years. Initial work addressed the conversion of logarithmic channel numbers into units of relative fluorescence. The design and use of calibration beads labeled with predefined amounts of dye allowed instrument-independent expression of fluorescence intensity in units of molecules of equivalent soluble fluorochrome (MESF). This method was refined by the combined use of such standards with monoclonal antibodies (mAb) conjugated 1:1 with phycoerythrin (PE), allowing translation of fluorescence intensity into numbers of antibodies bound per cell. Alternatively, the use of 1:1 PE-conjugated mAb under the assumption that CD4+ lymphocytes reproducibly bind 50,000 CD4 mAb molecules was proposed to convert units of relative fluorescence intensity into units of antibodies bound per cell. The use of antibody-binding capacity as a surrogate marker for quantification of Ag expression was addressed more directly by the development of antibody-binding standards. The quantitative indirect immunofluorescence assay is based on beads labeled with various amounts of CD5 mAb that calibrate the binding of the secondary antibody in units of antibody-binding capacity. Alternatively, goat anti-mouse-labeled calibration beads have been developed. Published results obtained with the latter calibrators showed an unexpected inaccuracy. The different ways in which calibrators and cells under study bind mAb (i.e., Fab mediated versus Fc mediated) may have contributed to this variation. Recently, the use of stabilized cell populations expressing Ag in a specified range of concentrations has been proposed as an Ag-specific calibration system of mAb binding. We identify several issues on the level of instrumentation, reagents, and cells under study that should be solved to allow standardization of quantitative assessments of immunofluorescence intensity.
Animals↗
Performance of calibration standards for antigen quantitation with flow cytometry.
In the frame of the activities initiated by the Task Force for Antigen Quantitation of the European Working Group on Clinical Cell Analysis (EWGCCA), an experiment was conducted to evaluate microbead standards used for quantitative flow cytometry (QFCM). An unified window of analysis (UWA) was established on three different instruments (EPICS XL [Coulter Corporation, Miami, FL], FACScan and FACS Calibur [Becton Dickinson, San Jose, CA]) with QC3 microbeads (FCSC, PR). By using this defined fluorescence intensity scale, the performance of several monoclonal antibodies directed to CD3, CD4, and CD8 (conjugated and unconjugated), from three manufacturers (BDIS, Coulter [Immunotech], and DAKO) was tested. In addition, the QIFI system (DAKO) and QuantiBRITE (BDIS), and a method of relative fluorescence intensity (RFI, method of Giorgi), were compared. mAbs reacting with three more antigens, CD16, CD19, and CD38 were tested on the FACScan instrument. Quantitation was carried out using a single batch of cryopreserved peripheral blood leukocytes, and all tests were performed as single color analyses. Significant correlations were observed between the antibody-binding capacity (ABC) values of the same CD antigen measured with various calibrators and with antibodies differing in respect to vendor, labeling and possible epitope recognition. Despite the significant correlations, the ABC values of most monoclonal antibodies differed by 20-40% when determined by the different fluorochrome conjugates and different calibrators. The results of this study indicate that, at the present stage of QFCM consistent ABC values may be attained between laboratories provided that a specific calibration system is used including specific calibrators, reagents, and protocols.
Antibodies, Monoclonal↗
Identification and characterization of the human adipocyte apM-1 promoter.
The human adipocyte-specific apM-1 gene encodes a secretory protein of the adipose tissue and seems to play a role in the pathogenesis of obesity. A 1.3 kb amount of the proximal promoter region has been cloned and analyzed for the presence of putative transcription factor binding sites. Several binding sites known to be involved in adipogenesis and regulation of adipocyte-specific genes (C/EBP, SREBP) are present. No TATA box, but a classical CCAAT box could be identified. To confirm functionality and cell specificity of the 1.3 kb promoter, a series of 5'-deleted fragments were ligated in front of the luciferase gene and the constructs were transfected into 3T3-L1 adipocytes. The reporter gene was effectively transcribed, as demonstrated by the expression of enzyme activity. The 5'-end of the human cDNA was completed by 5'-RACE-PCR. Several alternative transcription start sites were detected by RNase protection assay and primer extension analysis. In addition, an exon/intron boundary was mapped at the extreme 5'-end of the cDNA sequence. Genomic Southern blotting suggests that the human apM-1 gene is a single copy gene.
Adipocytes↗
Increased bioavailability of nitric oxide after lipid-lowering therapy in hypercholesterolemic patients: a randomized, placebo-controlled, double-blind study.
BACKGROUND: Impaired endothelium-dependent vasodilation is an early sign of atherosclerosis in hypercholesterolemic patients. We hypothesized that lipid-lowering therapy can improve endothelial function and that this effect is mainly mediated by increased bioavailability of nitric oxide (NO). METHODS AND RESULTS: In a randomized, double-blind, placebo-controlled trial, we studied 29 patients (age, 50+/-12 years) with hypercholesterolemia (LDL cholesterol > or = 160 mg/dL) randomly assigned to receive either fluvastatin (40 mg twice daily; 17 patients) or placebo (12 patients). Forearm blood flow was measured by plethysmography before and after 24 weeks of treatment. Endothelium-dependent vasodilation was assessed by intra-arterial infusion of acetylcholine (ACh; 3, 12, 24, and 48 microg/min) and basal NO synthesis rate by intra-arterial infusion of NG-monomethyl-L-arginine (L-NMMA; 1, 2, and 4 micromol/min). Simultaneous intra-arterial infusion of L-NMMA (4 micromol/min) and ACh (12, 24, and 48 microg/min) was used to test whether any increase in endothelium-dependent vasodilation after lipid-lowering therapy could be blocked by this NO synthase inhibitor. Endothelium-dependent vasodilation improved significantly after 24 weeks of lipid-lowering therapy compared with before therapy (ACh 24 microg/min: 240+/-34% before versus 347+/-50% after therapy; P< or =0.01) and placebo (changes between after and before therapy with ACh 24 microg/min: 108+/-39% for fluvastatin versus -26+/-32% for placebo; P< or =0.05). This improvement in endothelium-dependent vasodilation could be blocked by simultaneous administration of L-NMMA (ACh 24 microg/min plus L-NMMA 4 micromol/min: 170+/-69% before versus 219+/-47% after treatment; P=NS). CONCLUSIONS: Lipid-lowering therapy with fluvastatin can improve disturbed endothelial function in hypercholesterolemic patients compared with placebo. This improvement is mediated by increased bioavailability of NO.
Acetylcholine↗
Flow cytometric enumeration of CD34+ hematopoietic stem and progenitor cells. European Working Group on Clinical Cell Analysis.
The need for a rapid and reliable marker for the engraftment potential of hematopoietic stem and progenitor cell (HPC) transplants has led to the development of flow cytometric assays to quantitate such cells on the basis of their expression of CD34. The variability associated with enumeration of low-frequency cells (i.e., as low as 0.1% or 5 cells/microl) is exceedingly large, but recent developments have improved the accuracy and precision of the assay. Here, we review and compare the major techniques. Based on the current state of the art, we recommend 1) bright fluorochrome conjugates of class II or III monoclonal antibodies (mAbs) that detect all glycoforms of CD34, 2) use of a vital nucleic acid dye to exclude platelets, unlysed red cells, and debris or use of 7-amino actinomycin D to exclude dead cells during data acquisition, 3) counterstaining with CD45 mAb to be included in the definition of HPC, 4) during list mode data analysis, Boolean gating to resolve the CD34+ HPCs from irrelevant cell populations on the basis of the low levels of CD45 expression and low sideward light-scatter signals of HPCs, 5) inclusion of CD34dim and CD34bright populations in the CD34+ cell count, 6) omission of the negative control staining, and 7) for apheresis products, enumeration of at least 100 CD34+ cells to ensure a 10% precision. Unresolved technical questions are 1) the replacement of conventional dual-platform by single-platform assay formats, i.e., derivation of absolute CD34+ cell counts from a single flow cytometric assessment instead of from combined flow cytometer (percent CD34+) and hematology analyzer (absolute leukocyte count) data, 2) the cross-calibration of the available single-platform assays, and 3) the optimal method for sample preparation. An important clinical question to be addressed is the definition of the precise phenotypes and required numbers of HPCs responsible for short- and long-term recovery to optimize HPC transplant strategies.
Antigens, CD34↗
Genomic organization, promoter cloning, and chromosomal localization of the Dif-2 gene.
We describe the genomic organization and the functional promoter of the monocyte specific gene Dif-2, the human homologue to genes in mouse (gly96) and rat (PRG1), that is downregulated during cell differentiation. The Dif-2 gene consists of two exons and a single intron of 112 bp in length. RNase protection assay indicates one major transcription start site. Sequence analysis reveals several consensus sequences for transcription factors including NF-kappa B, C/EBP, SP1, and the lack of a classical TATA-box. To demonstrate promoter activity, DNA fragments of the Dif-2 5'-flanking region were ligated upstream to the luciferase gene and transfected into HepG2 and HeLa cells. A minimal promoter element between nt -158 and nt +74 containing NF-kappa B and SP1 binding sites was shown to be sufficient for basal activity. These transcription factor binding sites, which are conserved between Dif-2, gly96, and PRG1 promoter regions, indicate a significant role for Dif-2 expression and may explain LPS and C2-ceramide sensitivity. The Dif-2 gene was mapped to chromosome 6p21.3 using in situ hybridization technique.
Animals↗
Molecular cloning of human caveolin 3.
We isolated a full-length cDNA encoding human caveolin 3, which is 72% and 59% homologous to human caveolin 1 and caveolin 2, respectively. Human caveolin 3 protein contains the 'caveolin signature sequence' and the 33 amino acids spanning intramembrane domain common to all caveolins. Northern blot analysis indicates that the caveolin 3 transcript is 1.6 kb in size and exclusively detectable in muscle tissue.
Amino Acid Sequence↗
Different missense mutations in histidine-108 of lysosomal acid lipase cause cholesteryl ester storage disease in unrelated compound heterozygous and hemizygous individuals.
Cholesteryl ester storage disease (CESD) and Wolman disease (WD) are both autosomal recessive disorders associated with reduced activity of lysosomal acid lipase (LAL), that leads to the tissue accumulation of cholesteryl esters in endosomes and lysosomes. WD is caused by genetic defects of LAL that leave no residual enzymatic activity, while in CESD patients a residual LAL activity can be identified. We have analyzed the LAL cDNA in three CESD patients from two nonrelated families and identified the mutations responsible for the disease. The associated genetic defects characterized revealed compound heterozygosity for a splice defect leading to skipping of exon 8, due to a G-->A transition at position -1 of the exon 8 splice donor site, and a point mutation leading to a Hisl08Pro change (CAT-->CCT) in two patients (siblings) with mild CESD phenotype. A further CESD patient was hemizygous for a His108-->Arg missense mutation (CAT-->CGT) in combination with a partial deletion of the LAL gene and was affected more severely. Expression of the LAL enzymes with the His108-->Pro and His108-->Arg mutation in insect cells revealed residual enzymatic activities of 4.6% versus 2.7%, respectively, compared with controls. Therefore, His108 seems to play a crucial role in folding or catalytic activity of the lysosomal acid lipase. This is the first description of two different, naturally occurring mutations involving the same amino acid residue in the lysosomal acid lipase in unrelated CESD patients. Moreover, our results demonstrate that the variable manifestation of CESD can be explained by mutation-dependent, variable inactivation of the LAL enzyme.
Amino Acid Substitution↗
Automated free-solution isotachophoresis: instrumentation and fractionation of human serum proteins.
An automated free-solution isotachophoresis system (FS-ITP) for preparative fractionation of biopolymers is described, operated in a batch mode. The dimension of the separation chamber allows an up to 1200-fold higher sample load compared to separation in capillaries of 180 microm inner diameter as used in analytical capillary isotachophoresis (C-ITP). The preparative capacity of the system is within the milligram range. The method is fully compatible with analytical C-ITP, which is essential for preparative-scale isotachophoresis with regard to optimization of electrolyte systems and the search for suitable spacers. As a model application the fractionation of human serum proteins is reported. The collected fractions were analyzed by C-ITP and agarose gel electrophoresis.
Blood Proteins↗
Preparation of Golgi subfractions with free-solution isotachophoresis: analysis of sphingomyelin synthesis in Golgi subfractions from rat liver.
A new displacement electrophoresis technique, termed free-solution isotachophoresis (FS-ITP) was used for the analysis of sphingolipid metabolism in Golgi subfractions. The discontinuous electrolyte system enables tissue-derived membrane vesicles to be separated and purified due to their polarity patterns in a mobility gradient. In this study total Golgi apparatus obtained from rat liver by discontinuous density gradient centrifugation was subfractionated by preparative FS-ITP, yielding enzymatically active cis-, medial-, and trans-Golgi subfractions. These membrane vesicles were assayed by the following established enzyme marker activities: NADH cytochrome c reductase (cis-Golgi), NADP phosphatase (medial-Golgi), and thiamine pyrophosphatase (trans-Golgi). The activity of phosphatidylcholine:ceramide phosphocholine transferase, a sphingomyelin synthesizing enzyme, is attributed to the cis- and medial-Golgi-derived subfractions. Analysis of Golgi lipids revealed a decline in membranous ceramide along the cis- to trans-Golgi polarity axis. Furthermore, significant amounts of newly synthesized sphingomyelin and diacylglycerol are transferred from the medial/cis- to the trans-Golgi compartment. The FS-ITP system is well suited for micropreparative experimental applications, as demonstrated by studies on phosphatidylcholine:ceramide phosphocholine transferase activity in Golgi membrane vesicles of rat liver obtained by FS-ITP.
Animals↗
T-lymphocytes and monocytes in atherogenesis.
Atherosclerosis is characterized as a chronic inflammatory-fibroproliferative disease of the vessel wall. The attachment of monocytes and T-lymphocytes to the injured endothelium followed by their migration into the intima is one of the first and most crucial steps in lesion development. The co-localization of CD4+ T-cells and macrophages in the lesion, the abundant expression of HLA Class II molecules and the co-stimulatory molecule CD40 and its ligand (CD40L) indicate a contribution of cell-mediated immunity to atherogenesis. Transgenic mouse models revealed that dependent on the model T- and B-cells may promote lesion progression, monocytes and macrophages are in contrast essential for the development of atherosclerotic lesions. Apart from the local process in the vessel wall, systemic signs of an inflammatory reaction are also associated with lesion development. Thus plasma levels of C-reactive protein and fibrinogen and the white blood cell count are positively correlated to the risk of cardiovascular disease. Recently, an inflammatory phenotype of circulating peripheral blood monocytes could be demonstrated as a specific cellular correlate to lipid and lipoprotein risk factors. Thus the pool size of LPS receptor (CD14)dim and Fc gamma IIIa receptor (CD16a)+ monocytes positively correlates to plasma cholesterol levels, to triglycerides levels and to the apolipoprotein E4 (apo E4) phenotype in contrast to a negative correlation to the high density lipoprotein (HDL) cholesterol concentration. This CD14dim CD16a+ monocytes are further characterized by a high expression of beta 1- and beta 2-integrins, suggesting a higher capacity for attachment at sites of inflammation. A proinflammatory cytokine pattern and an expansion of these cells in other inflammatory diseases are indicating that these cells promote the inflammatory process during atherogenesis. Surface expression of the activation antigen CD45RA on monocytes in correlation to plasma LDL cholesterol and Lp(a) levels further indicates an inflammatory reaction. Regarding the potential mechanisms of the phenotypic changes of peripheral blood monocytes, in a serum free in vitro differentiation model supplemented with M-CSF monocytes from probands which are homozygous for apo E4 showed a significantly higher increase of CD16a expression compared to apo E3/E3 cells indicating that a genetic polymorphism of a single apolipoprotein gene locus may affect monocyte differentiation. The further characterization of the cellular immunology of monocytes and T-lymphocytes in lesion development will provide new specific diagnostic and therapeutic targets in atherogenesis.
Animals↗
Does lipoprotein(a) impair endothelial function?
OBJECTIVES: This study was undertaken to test the hypothesis that lipoprotein(a) [Lp(a)] impairs endothelial function. BACKGROUND: Elevated Lp(a) plasma levels have been demonstrated to be associated with an increased risk of coronary heart disease. In atherosclerosis, endothelial dysfunction is known to be an early indicator of vascular changes. However, the effect of Lp(a) on nitric oxide (NO)-dependent vasodilator response has not yet been determined. We therefore examined the influence of Lp(a) on basal and stimulated NO-mediated vasodilator response in the forearm vascular bed. METHODS: Strain gauge plethysmography was used to measure changes in forearm blood flow produced by intraarterial infusion of increasing doses of acetylcholine (3, 12, 24 and 48 microg/min), sodium nitroprusside (200, 800 and 3,200 ng/min) and N-monomethyl L-arginine (L-NMMA) (1, 2 and 4 micromol/min) in 57 white subjects (mean age +/- SD 37 +/- 14 years). Lp(a) plasma concentrations were determined by rocket immunoelectrophoresis. RESULTS: Endothelium-dependent vasodilation tested by intraarterial acetylcholine and endothelium-independent vascular relaxation tested by intraarterial sodium nitroprusside were not correlated with Lp(a). Similarly, no significant differences in forearm blood flow changes were observed when patients were classified into tertiles according to their individual Lp(a) concentration. In contrast, changes in forearm blood flow after intraarterial L-NMMA indicating basal production and release of NO differed significantly among tertiles. Patients in the highest Lp(a) tertile (49.2 +/- 20.3 mg/dl) had a much greater vasoconstrictive response to L-NMMA than patients in the lowest Lp(a) tertile (4.8 +/- 2.5 mg/dl): 2 micromol/min of L-NMMA, -23.6 +/- 22.5% vs. -10.4 +/- 9.1% (p < 0.02); 4 micromol/min of L-NMMA, -27.8 +/- 10.3% vs. -17.6 +/- 9.9% (p < 0.03). Lp(a) plasma level consistently correlated negatively with the forearm blood flow responses to 4 micromol/min of intraarterial L-NMMA (r = -0.38, p < 0.01). Multiple stepwise regression analysis of variables, including total and high and low density lipoprotein cholesterol, further confirmed that plasma Lp(a) remained a significant independent determinant of forearm blood flow changes in response to L-NMMA (p < 0.02). CONCLUSIONS: The endothelium-dependent vasoconstrictive response to L-NMMA was enhanced in subjects with relatively high Lp(a) plasma levels, suggesting an increased basal production and release of NO. This response seemed to reflect a compensatory mechanism of the endothelium to yet unknown Lp(a)-induced atherosclerotic effects.
Acetylcholine↗
Chronic inflammatory demyelinating polyradiculoneuropathy: superiority of protein A immunoadsorption over plasma exchange treatment.
We present a patient with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) who was treated regularly with plasma exchanges (PE) because response to other therapies including i.v. immunoglobulins was not adequate. To reduce nonspecific protein losses due to repeated PE and increase IgG-removal, immunoadsorption (i.a.)-therapy using sepharose-bound protein A was initiated. Retrospective analysis of clinical data including muscle strength and walking distance shows that IA led to more rapid and greater functional improvement than PE in this patient with no relevant side effects. After 3 years of therapy lymphoma was diagnosed and treated. The patient had no relapses of CIDP for 17 months, when his functional status deteriorated again necessitating further IA-therapy. It is concluded that IgG removal by IA in CIDP is more effective and has fewer complications than PE. Due to the chronic course of CIDP requiring repeated interventions IA is also not more expensive than PE.
Chronic Disease↗
Lipoprotein(a) apheresis in severe coronary heart disease: an immunoadsorption method.
Lipoprotein(a) (Lp[a]) is associated with an increased cardiovascular risk. It is similar to low-density lipoprotein with an additional molecule of apo A covalently linked to apo B-100 by one disulfide bridge. Apo A is highly homologous to plasminogen. The kringle 4 motive of plasminogen is repeated between 10 and 40 times in apo (a). Currently, there is no drug therapy available to lower Lp(a). Since October 1993, we have carried out over 160 immunoadsorption treatments on 3 patients with elevated Lp(a) as their only risk factor and a history of myocardial infarction. Lp(a) was removed from plasma by sepharose coupled anti-Lp(a) columns. Lp(a) levels were lowered from above 170 mg/dl to below 30 mg/dl immediately after Lp(a) apheresis. To achieve this, the patient's plasma volume had to be treated 2 to 3 times. Nonspecific protein loss during column changes remained negligible. There were no serious unwanted effects during or after treatment. Minor circulatory problems (tachycardia, flush) occurred in 11% of the treatments but only with plasma flow rates above 55 ml/min. In 1 patient, coronary angiography after 2 years and in another patient after 1 year showed no progression. The third patient has not yet had repeat coronary angiography. Like the others, he reported subjective improvement after 1 year of apheresis. It is concluded that Lp(a) apheresis may retard progression of atherosclerosis in patients with selective Lp(a) elevation. Further studies to support this hypothesis are needed.
Adult↗