The design phase of an algorithm's implementation is confronted with the issues of efficiency... more The design phase of an algorithm's implementation is confronted with the issues of efficiency, flexibility, and ease-of-use. In this paper, we suggest a concept that greatly increases the flexibility of an implementation without sacrificing its ease-of-use. The loss in terms of efficiency is small. We demonstrate the advantages of our concept at a C++ implementation of a simple rectangleintersection algorithm, which follows the well-known sweep-line paradigm. We lead the reader from a naive interface in a step-by-step guide to an interface offering full flexibility. The gain in flexibility can reduce implementation effort by facilitating code reusage. Reusability in turn helps to achieve correctness since more users mean more testing. Though most of the ingredients of our concept have already been suggested elsewhere, to our knowledge this is the first time that they are applied vigorously in a geometric setting. We include a thorough experimental analysis on random and real wor...
A 76-year-old female patient with symptomatic severe aortic stenosis was referred for transcathet... more A 76-year-old female patient with symptomatic severe aortic stenosis was referred for transcatheter aortic valve replacement (TAVR) due to high risk for open-heart surgery (logistic EuroSCORE [European System for Cardiac Operative Risk Evaluation] 23.6%) (1,2). Screening computed tomography scan noted a low origin of the right coronary artery (7 mm) (Figure 1). The heart team FI GURE 1 Multislice CT Scan Sagittal View Transcatheter aortic valve replacement screening computed tomography (CT) workup revealed a low origin of right coronary artery (7 mm). FIGURE 2 Occluded RCA Angiographic image (left anterior oblique 10 , cranial 14) after first inflation of the aortic ring of the Direct Flow 25-mm valve (Online Video 1). The left ventricular outflow tract ring is sealing with no trance of aortic regurgitation (Online Video 2). The aortic ring is occluding the ostium of the right coronary artery (RCA).
Research Direction for Developing an Infrastructure for Mobile & Wireless Systems: Consensus Report of the NSF Workshop Held on October 15, 2001 in Scottsdale, Arizona
P ULMONARY function can be divided into two phases: (1) ventilator!!, which involves the movement... more P ULMONARY function can be divided into two phases: (1) ventilator!!, which involves the movement of air into and out of the lungs; and (2) respirntory, which deals with the gaseous exchange between the alveoli and pulmonary circulation. Recent work on pulmonary function by Cournand, Motley, Comroe, and others has shown how much practical information can be gained from such studies. The determination of respiratory function, however, has remained, by and large, an experimental procedure. Measuring ventilatory function, in contrast to studies of gaseous exchange, is relatively simple and has been carried out to a limited extent by many physicians, using vital capacity as a yardstick of pulmonary integrity. Vital capacity, however, is a statistical measurement of limited diagnostic value unless the time factor is taken into account. Maximum voluntary ventilating capacity (M. V. V. C.), on the other hand, is a dynamic measurement which determines the maximum amount of air that can be moved into and out of the lungs over a given period of time, when the patient breathes as deeply and rapidly as possible. Our work deals with limited ventilatory function tests in an attempt to estimate their practical prognostic and diagnosic value.
Background:Multicapillary column ion-mobility spectrometry (MCC-IMS) may identify volatile compon... more Background:Multicapillary column ion-mobility spectrometry (MCC-IMS) may identify volatile components in exhaled gas. The authors therefore used MCC-IMS to evaluate exhaled gas in a rat model of sepsis, inflammation, and hemorrhagic shock.Methods:Male Sprague–Dawley rats were anesthetized and ventilated via tracheostomy for 10 h or until death. Sepsis was induced by cecal ligation and incision in 10 rats; a sham operation was performed in 10 others. In 10 other rats, endotoxemia was induced by intravenous administration of 10 mg/kg lipopolysaccharide. In a final 10 rats, hemorrhagic shock was induced to a mean arterial pressure of 35 ± 5 mmHg. Exhaled gas was analyzed with MCC-IMS, and volatile compounds were identified using the BS-MCC/IMS-analytes database (Version 1209; B&S Analytik, Dortmund, Germany).Results:All sham animals survived the observation period, whereas mean survival time was 7.9 h in the septic animals, 9.1 h in endotoxemic animals, and 2.5 h in hemorrhagic shock. ...
Let P be a set of points in Rd, and let � > 1 be a real number. We define the distance between... more Let P be a set of points in Rd, and let � > 1 be a real number. We define the distance between two points p,q 2 P as |pq|�, where |pq| denotes the standard Euclidean distance between p and q. We denote the traveling salesman problem under this distance function by Tsp(d,�). We design a 5-approximation algorithm for Tsp(2,2) and generalize this result to obtain an approximation factor of 3�−1 + p 6 � /3 for d = 2 and all � > 2. We also study the variant Rev-Tsp of the problem where the traveling salesman is allowed to revisit points. We present a polynomial-time approximation scheme for Rev- Tsp(2,�) with � > 2, and we show that Rev-Tsp(d,�) is apx-hard if d > 3 and � > 1. The apx-hardness proof carries over to Tsp(d,�) for the same parameter ranges.
Swine Hepatitis E virus (HEV) can be transmitted from pigs to humans causing hepatitis. A high pr... more Swine Hepatitis E virus (HEV) can be transmitted from pigs to humans causing hepatitis. A high prevalence of HEV in wild boar populations is reported for several European countries, but actual data for Germany are missing. During the hunting season from October to December 2007 liver, bile and blood samples were collected from wild boars in four different German regions. The samples were tested for HEV RNA by quantitative PCR (qPCR) and anti-HEV IgG antibodies by two different ELISAs and a Line immunoassay. A seroprevalence of 29.9% using ELISA and 26.2% in the Line immunoassay was determined. The seroprevalence rate varied greatly within the analysed regions. However, qPCR analysis revealed a higher prevalence of 68.2% positive animals with regional differences. Surprisingly, also adult wild sows and wild boars were highly HEV positive by qPCR. Compared to liver and serum samples, bile samples showed a higher rate of positive qPCR results. Sequencing and phylogenetic analysis of a 969 nt fragment within ORF 2 revealed that all isolates clustered within genotype 3 but differed in the subtype depending on the hunting spot. Isolates clustered within genotypes 3i, 3h, 3f and 3e. Within one population HEV isolates were closely related, but social groups of animals in close proximity might be infected with different subtypes. Two full-length genomes of subtypes 3i and 3e from two different geographic regions were generated. The wild boar is discussed as one of the main sources of human autochthonous infections in Germany.
A wild-caught male panther chameleon (Furcifer pardalis, previously known as Chamaleo pardalis) i... more A wild-caught male panther chameleon (Furcifer pardalis, previously known as Chamaleo pardalis) imported from Madagascar and of unknown age was presented to the Avian and Exotic Animal Clinic of Lafayette with a complaint of anorexia. The chameleon's diet consisted primarily of crickets, which the owner occasionally would dust with calcium supplement. Although physically vigorous, the patient was thin (52 g), exhibited poor coloration (Figure 1A), and had pale oral mucous membranes. Physical examination revealed 4 multifocal, poorly defined small bulges underneath the skin (not shown). Two of the bulges were located behind the left forearm, and the other 2 were located cranial to the right rear limb. As part of the diagnostic workup, heparinized blood samples were collected and used to prepare several air-dried smears and wet preparations. Most blood smears were stained with a rapid Romanowsky stain (Diff-Quik, Dade Diagnostics, Aguada, Puerto Rico).The remaining blood smears were later stained with an automated Romanowsky stain (Hematek, Bayer Diagnostics, Elkhart, Ind) at the Purdue University Veterinary Clinical Pathology Laboratory (Figure 1B). Other laboratory tests (clinical chemistry, PCV, CBC) were not done because of the limited amount of blood available.
Consumption of tobacco products is the most relevant risk factor for the development of bladder c... more Consumption of tobacco products is the most relevant risk factor for the development of bladder cancer beside occupational contributions. In order to investigate mechanisms of tobacco smoke components in bladder carcinogenesis we have introduced a primary epithelial cell culture system derived from porcine urinary bladder as a suitable representative for the corresponding human tissue under physiological conditions. Two independent readouts were selected as markers for genotoxic events. Changes in the expression level of several toxicologically relevant genes should serve as indicators for early response, while classical genotoxic endpoints monitored manifested damages. Here, we present the first results of our study with benzo(a)pyrene (BaP) as a member of polycyclic aromatic hydrocarbons (PAHs) found in tobacco smoke. Cells treated with BaP show a dramatic increase in the expression of CYP1A1 that appears to be both indicator of and contributor for BaP toxicity. Genes coding for other proteins relevant in xenobiotic metabolism, signal transduction or tumor suppression show moderate effects or no enhancement of their expression levels. Comet assay and micronucleus test did show a significant, dose-dependent increase in DNA damages or aberrations after cell division. While these effects are conforming to the response at the mRNA expression level, they are less pronounced and require rather higher dosages of the chemical.
Issues in Coordination Languages and Architectures About Coordination Coordination languages are ... more Issues in Coordination Languages and Architectures About Coordination Coordination languages are a class of programming languages expressly invented to manage the interactions among components of distributed software architetures. Gelernter and Carriero used the term Coordination in the following context: Programming = Computation + Coordination: They formulated this equation to explain the use of the coordination language Linda. Their point is that there should be a clear separation between the description of the agents of the computation and the description of their interaction in the overall architecture of a software system. On the one hand, such a separation facilitates the architectural reuse of code; on the other hand, the same interaction patterns occur in many di erent problems-so it becomes possible to reuse the coordination component as well! Usually coordination languages are not full-edged programming languages; rather, they are often deÿned as language extensions or scripting languages as they are mostly concerned with coordination issues. Roughly, coordination research concentrates on the following topics:
Proceedings of the National Academy of Sciences, 2004
The Hedgehog proteins are potent organizers of animal development. They carry a cholesterol ester... more The Hedgehog proteins are potent organizers of animal development. They carry a cholesterol ester at the C terminus of their signaling domain. The membrane anchoring mediated by this lipophilic modification was studied by means of an approach integrating cell biology, biochemistry, biophysics, and organic chemistry techniques. Sterol-modified and fluorescent-labeled Hedgehog-derived peptides and proteins were synthesized and investigated in biophysical and cell-biological assays. These experiments revealed that cholesterol alone anchors proteins to membranes with significant strength and half-times for spontaneous desorption of several hours. Its membrane anchoring ability is comparable to dual lipidation motifs such as double geranylgeranylation or S-palmitoylation plus S-farnesylation found in other lipidated proteins. The experiments also demonstrate that membrane binding changes dramatically if short lipidated peptides are equipped with a large protein. These data suggest that f...
Evaluation of Time Dependence and Interindividual Differences in Benzo[a]pyrene-MediatedCYP1A1Induction and Genotoxicity in Porcine Urinary Bladder Cell Cultures∗
Journal of Toxicology and Environmental Health, Part A, 2008
Exposure to tobacco smoke is an established cause of cancer in humans and cigarette smoking is a ... more Exposure to tobacco smoke is an established cause of cancer in humans and cigarette smoking is a risk factor for urinary bladder cancer development. Aromatic amines are believed responsible for the bladder-specific carcinogenic effect, but polycyclic aromatic hydrocarbons (PAHs) are also of potential relevance. Urothelial cells contain a number of xenobiotic-metabolizing enzymes, which enable them to convert pro-carcinogens into reactive intermediates. In a preceding study, it was demonstrated using cultured porcine urinary bladder epithelial cells (PUBEC) that CYP1A1 mRNA is induced in a potent manner by treatment with benzo[a]pyrene (BaP). In the present study, the time dependence of these effects was evaluated and whether PUBEC cultures derived from individual donors respond differently to BaP treatment was determined. CYP1A1 induction was analyzed by quantitative reverse-transcription polymerase chain reaction (RT-PCR), and genotoxic effects were studied using the Comet assay. Incubation of PUBEC with BaP increased CYP1A1 expression and induction of DNA strand breaks in a time-dependent manner. Interindividual differences were found between PUBEC cultures derived from several donor animals with respect to the response to BaP, such that the extent of CYP1A1 induction and magnitude of DNA damage was interrelated. Hence, individual differences in metabolic capacities and responsiveness to xenobiotics of urothelial cells from individual donors may be factors in susceptibility to genotoxic effects induced by PAHs.
GC–MS determination of creatinine in human biological fluids as pentafluorobenzyl derivative in clinical studies and biomonitoring: Inter-laboratory comparison in urine with Jaffé, HPLC and enzymatic assays
Journal of Chromatography B, 2010
In consideration of its relatively constant urinary excretion rate, creatinine in urine is a usef... more In consideration of its relatively constant urinary excretion rate, creatinine in urine is a useful biochemical parameter to correct the urinary excretion rate of endogenous and exogenous biomolecules. Assays based on the reaction of creatinine and picric acid first reported by Jaffé in 1886 still belong to the most frequently used laboratory approaches for creatinine measurement in urine. Further analytical methods for creatinine include HPLC-UV, GC-MS, and LC-MS and LC-MS/MS approaches. In the present article we report on the development, validation and biomedical application of a new GC-MS method for the reliable quantitative determination of creatinine in human urine, plasma and serum. This method is based on the derivatization of creatinine (d(0)-Crea) and the internal standard [methyl-trideutero]creatinine (d(3)-Crea) with pentafluorobenzyl (PFB) bromide in the biological sample directly or after dilution with phosphate buffered saline, extraction of the reaction products with toluene and quantification in 1-μl aliquots of the toluene extract by selected-ion monitoring of m/z 112 for d(0)-Crea-PFB and m/z 115 for d(3)-Crea-PFB in the electron-capture negative-ion chemical ionization mode. The limit of detection of the method is 100 amol of creatinine. In an inter-laboratory study on urine samples from 100 healthy subjects, the GC-MS method was used to test the reliability of currently used Jaffé, enzymatic and HPLC assays in clinical and occupational studies. The results of the inter-laboratory study indicate that all three tested methods allow for satisfactory quantification of creatinine in human urine. The GC-MS method is suitable for use as a reference method for urinary creatinine in humans. In serum, creatine was found to contribute to creatinine up to 20% when measured by the present GC-MS method. The application of the GC-MS method can be extended to other biological samples such as saliva.
Exact decoupling of the Dirac Hamiltonian. I. General theory
The Journal of Chemical Physics, 2004
Exact decoupling of positive- and negative-energy states in relativistic quantum chemistry is dis... more Exact decoupling of positive- and negative-energy states in relativistic quantum chemistry is discussed in the framework of unitary transformation techniques. The obscure situation that each scheme of decoupling transformations relies on different, but very special parametrizations of the employed unitary matrices is critically analyzed. By applying the most general power series ansatz for the parametrization of the unitary matrices it is shown that all transformation protocols for decoupling the Dirac Hamiltonian have necessarily to start with an initial free-particle Foldy–Wouthuysen step. The purely numerical iteration scheme applying X-operator techniques to the Barysz–Sadlej–Snijders (BSS) Hamiltonian is compared to the analytical schemes of the Foldy–Wouthuysen (FW) and Douglas–Kroll–Hess (DKH) approaches. Relying on an illegal 1/c expansion of the Dirac Hamiltonian around the nonrelativistic limit, any higher-order FW transformation is in principle ill defined and doomed to f...
The design phase of an algorithm's implementation is confronted with the issues of efficiency... more The design phase of an algorithm's implementation is confronted with the issues of efficiency, flexibility, and ease-of-use. In this paper, we suggest a concept that greatly increases the flexibility of an implementation without sacrificing its ease-of-use. The loss in terms of efficiency is small. We demonstrate the advantages of our concept at a C++ implementation of a simple rectangleintersection algorithm, which follows the well-known sweep-line paradigm. We lead the reader from a naive interface in a step-by-step guide to an interface offering full flexibility. The gain in flexibility can reduce implementation effort by facilitating code reusage. Reusability in turn helps to achieve correctness since more users mean more testing. Though most of the ingredients of our concept have already been suggested elsewhere, to our knowledge this is the first time that they are applied vigorously in a geometric setting. We include a thorough experimental analysis on random and real wor...
A 76-year-old female patient with symptomatic severe aortic stenosis was referred for transcathet... more A 76-year-old female patient with symptomatic severe aortic stenosis was referred for transcatheter aortic valve replacement (TAVR) due to high risk for open-heart surgery (logistic EuroSCORE [European System for Cardiac Operative Risk Evaluation] 23.6%) (1,2). Screening computed tomography scan noted a low origin of the right coronary artery (7 mm) (Figure 1). The heart team FI GURE 1 Multislice CT Scan Sagittal View Transcatheter aortic valve replacement screening computed tomography (CT) workup revealed a low origin of right coronary artery (7 mm). FIGURE 2 Occluded RCA Angiographic image (left anterior oblique 10 , cranial 14) after first inflation of the aortic ring of the Direct Flow 25-mm valve (Online Video 1). The left ventricular outflow tract ring is sealing with no trance of aortic regurgitation (Online Video 2). The aortic ring is occluding the ostium of the right coronary artery (RCA).
Research Direction for Developing an Infrastructure for Mobile & Wireless Systems: Consensus Report of the NSF Workshop Held on October 15, 2001 in Scottsdale, Arizona
P ULMONARY function can be divided into two phases: (1) ventilator!!, which involves the movement... more P ULMONARY function can be divided into two phases: (1) ventilator!!, which involves the movement of air into and out of the lungs; and (2) respirntory, which deals with the gaseous exchange between the alveoli and pulmonary circulation. Recent work on pulmonary function by Cournand, Motley, Comroe, and others has shown how much practical information can be gained from such studies. The determination of respiratory function, however, has remained, by and large, an experimental procedure. Measuring ventilatory function, in contrast to studies of gaseous exchange, is relatively simple and has been carried out to a limited extent by many physicians, using vital capacity as a yardstick of pulmonary integrity. Vital capacity, however, is a statistical measurement of limited diagnostic value unless the time factor is taken into account. Maximum voluntary ventilating capacity (M. V. V. C.), on the other hand, is a dynamic measurement which determines the maximum amount of air that can be moved into and out of the lungs over a given period of time, when the patient breathes as deeply and rapidly as possible. Our work deals with limited ventilatory function tests in an attempt to estimate their practical prognostic and diagnosic value.
Background:Multicapillary column ion-mobility spectrometry (MCC-IMS) may identify volatile compon... more Background:Multicapillary column ion-mobility spectrometry (MCC-IMS) may identify volatile components in exhaled gas. The authors therefore used MCC-IMS to evaluate exhaled gas in a rat model of sepsis, inflammation, and hemorrhagic shock.Methods:Male Sprague–Dawley rats were anesthetized and ventilated via tracheostomy for 10 h or until death. Sepsis was induced by cecal ligation and incision in 10 rats; a sham operation was performed in 10 others. In 10 other rats, endotoxemia was induced by intravenous administration of 10 mg/kg lipopolysaccharide. In a final 10 rats, hemorrhagic shock was induced to a mean arterial pressure of 35 ± 5 mmHg. Exhaled gas was analyzed with MCC-IMS, and volatile compounds were identified using the BS-MCC/IMS-analytes database (Version 1209; B&S Analytik, Dortmund, Germany).Results:All sham animals survived the observation period, whereas mean survival time was 7.9 h in the septic animals, 9.1 h in endotoxemic animals, and 2.5 h in hemorrhagic shock. ...
Let P be a set of points in Rd, and let � > 1 be a real number. We define the distance between... more Let P be a set of points in Rd, and let � > 1 be a real number. We define the distance between two points p,q 2 P as |pq|�, where |pq| denotes the standard Euclidean distance between p and q. We denote the traveling salesman problem under this distance function by Tsp(d,�). We design a 5-approximation algorithm for Tsp(2,2) and generalize this result to obtain an approximation factor of 3�−1 + p 6 � /3 for d = 2 and all � > 2. We also study the variant Rev-Tsp of the problem where the traveling salesman is allowed to revisit points. We present a polynomial-time approximation scheme for Rev- Tsp(2,�) with � > 2, and we show that Rev-Tsp(d,�) is apx-hard if d > 3 and � > 1. The apx-hardness proof carries over to Tsp(d,�) for the same parameter ranges.
Swine Hepatitis E virus (HEV) can be transmitted from pigs to humans causing hepatitis. A high pr... more Swine Hepatitis E virus (HEV) can be transmitted from pigs to humans causing hepatitis. A high prevalence of HEV in wild boar populations is reported for several European countries, but actual data for Germany are missing. During the hunting season from October to December 2007 liver, bile and blood samples were collected from wild boars in four different German regions. The samples were tested for HEV RNA by quantitative PCR (qPCR) and anti-HEV IgG antibodies by two different ELISAs and a Line immunoassay. A seroprevalence of 29.9% using ELISA and 26.2% in the Line immunoassay was determined. The seroprevalence rate varied greatly within the analysed regions. However, qPCR analysis revealed a higher prevalence of 68.2% positive animals with regional differences. Surprisingly, also adult wild sows and wild boars were highly HEV positive by qPCR. Compared to liver and serum samples, bile samples showed a higher rate of positive qPCR results. Sequencing and phylogenetic analysis of a 969 nt fragment within ORF 2 revealed that all isolates clustered within genotype 3 but differed in the subtype depending on the hunting spot. Isolates clustered within genotypes 3i, 3h, 3f and 3e. Within one population HEV isolates were closely related, but social groups of animals in close proximity might be infected with different subtypes. Two full-length genomes of subtypes 3i and 3e from two different geographic regions were generated. The wild boar is discussed as one of the main sources of human autochthonous infections in Germany.
A wild-caught male panther chameleon (Furcifer pardalis, previously known as Chamaleo pardalis) i... more A wild-caught male panther chameleon (Furcifer pardalis, previously known as Chamaleo pardalis) imported from Madagascar and of unknown age was presented to the Avian and Exotic Animal Clinic of Lafayette with a complaint of anorexia. The chameleon's diet consisted primarily of crickets, which the owner occasionally would dust with calcium supplement. Although physically vigorous, the patient was thin (52 g), exhibited poor coloration (Figure 1A), and had pale oral mucous membranes. Physical examination revealed 4 multifocal, poorly defined small bulges underneath the skin (not shown). Two of the bulges were located behind the left forearm, and the other 2 were located cranial to the right rear limb. As part of the diagnostic workup, heparinized blood samples were collected and used to prepare several air-dried smears and wet preparations. Most blood smears were stained with a rapid Romanowsky stain (Diff-Quik, Dade Diagnostics, Aguada, Puerto Rico).The remaining blood smears were later stained with an automated Romanowsky stain (Hematek, Bayer Diagnostics, Elkhart, Ind) at the Purdue University Veterinary Clinical Pathology Laboratory (Figure 1B). Other laboratory tests (clinical chemistry, PCV, CBC) were not done because of the limited amount of blood available.
Consumption of tobacco products is the most relevant risk factor for the development of bladder c... more Consumption of tobacco products is the most relevant risk factor for the development of bladder cancer beside occupational contributions. In order to investigate mechanisms of tobacco smoke components in bladder carcinogenesis we have introduced a primary epithelial cell culture system derived from porcine urinary bladder as a suitable representative for the corresponding human tissue under physiological conditions. Two independent readouts were selected as markers for genotoxic events. Changes in the expression level of several toxicologically relevant genes should serve as indicators for early response, while classical genotoxic endpoints monitored manifested damages. Here, we present the first results of our study with benzo(a)pyrene (BaP) as a member of polycyclic aromatic hydrocarbons (PAHs) found in tobacco smoke. Cells treated with BaP show a dramatic increase in the expression of CYP1A1 that appears to be both indicator of and contributor for BaP toxicity. Genes coding for other proteins relevant in xenobiotic metabolism, signal transduction or tumor suppression show moderate effects or no enhancement of their expression levels. Comet assay and micronucleus test did show a significant, dose-dependent increase in DNA damages or aberrations after cell division. While these effects are conforming to the response at the mRNA expression level, they are less pronounced and require rather higher dosages of the chemical.
Issues in Coordination Languages and Architectures About Coordination Coordination languages are ... more Issues in Coordination Languages and Architectures About Coordination Coordination languages are a class of programming languages expressly invented to manage the interactions among components of distributed software architetures. Gelernter and Carriero used the term Coordination in the following context: Programming = Computation + Coordination: They formulated this equation to explain the use of the coordination language Linda. Their point is that there should be a clear separation between the description of the agents of the computation and the description of their interaction in the overall architecture of a software system. On the one hand, such a separation facilitates the architectural reuse of code; on the other hand, the same interaction patterns occur in many di erent problems-so it becomes possible to reuse the coordination component as well! Usually coordination languages are not full-edged programming languages; rather, they are often deÿned as language extensions or scripting languages as they are mostly concerned with coordination issues. Roughly, coordination research concentrates on the following topics:
Proceedings of the National Academy of Sciences, 2004
The Hedgehog proteins are potent organizers of animal development. They carry a cholesterol ester... more The Hedgehog proteins are potent organizers of animal development. They carry a cholesterol ester at the C terminus of their signaling domain. The membrane anchoring mediated by this lipophilic modification was studied by means of an approach integrating cell biology, biochemistry, biophysics, and organic chemistry techniques. Sterol-modified and fluorescent-labeled Hedgehog-derived peptides and proteins were synthesized and investigated in biophysical and cell-biological assays. These experiments revealed that cholesterol alone anchors proteins to membranes with significant strength and half-times for spontaneous desorption of several hours. Its membrane anchoring ability is comparable to dual lipidation motifs such as double geranylgeranylation or S-palmitoylation plus S-farnesylation found in other lipidated proteins. The experiments also demonstrate that membrane binding changes dramatically if short lipidated peptides are equipped with a large protein. These data suggest that f...
Evaluation of Time Dependence and Interindividual Differences in Benzo[a]pyrene-MediatedCYP1A1Induction and Genotoxicity in Porcine Urinary Bladder Cell Cultures∗
Journal of Toxicology and Environmental Health, Part A, 2008
Exposure to tobacco smoke is an established cause of cancer in humans and cigarette smoking is a ... more Exposure to tobacco smoke is an established cause of cancer in humans and cigarette smoking is a risk factor for urinary bladder cancer development. Aromatic amines are believed responsible for the bladder-specific carcinogenic effect, but polycyclic aromatic hydrocarbons (PAHs) are also of potential relevance. Urothelial cells contain a number of xenobiotic-metabolizing enzymes, which enable them to convert pro-carcinogens into reactive intermediates. In a preceding study, it was demonstrated using cultured porcine urinary bladder epithelial cells (PUBEC) that CYP1A1 mRNA is induced in a potent manner by treatment with benzo[a]pyrene (BaP). In the present study, the time dependence of these effects was evaluated and whether PUBEC cultures derived from individual donors respond differently to BaP treatment was determined. CYP1A1 induction was analyzed by quantitative reverse-transcription polymerase chain reaction (RT-PCR), and genotoxic effects were studied using the Comet assay. Incubation of PUBEC with BaP increased CYP1A1 expression and induction of DNA strand breaks in a time-dependent manner. Interindividual differences were found between PUBEC cultures derived from several donor animals with respect to the response to BaP, such that the extent of CYP1A1 induction and magnitude of DNA damage was interrelated. Hence, individual differences in metabolic capacities and responsiveness to xenobiotics of urothelial cells from individual donors may be factors in susceptibility to genotoxic effects induced by PAHs.
GC–MS determination of creatinine in human biological fluids as pentafluorobenzyl derivative in clinical studies and biomonitoring: Inter-laboratory comparison in urine with Jaffé, HPLC and enzymatic assays
Journal of Chromatography B, 2010
In consideration of its relatively constant urinary excretion rate, creatinine in urine is a usef... more In consideration of its relatively constant urinary excretion rate, creatinine in urine is a useful biochemical parameter to correct the urinary excretion rate of endogenous and exogenous biomolecules. Assays based on the reaction of creatinine and picric acid first reported by Jaffé in 1886 still belong to the most frequently used laboratory approaches for creatinine measurement in urine. Further analytical methods for creatinine include HPLC-UV, GC-MS, and LC-MS and LC-MS/MS approaches. In the present article we report on the development, validation and biomedical application of a new GC-MS method for the reliable quantitative determination of creatinine in human urine, plasma and serum. This method is based on the derivatization of creatinine (d(0)-Crea) and the internal standard [methyl-trideutero]creatinine (d(3)-Crea) with pentafluorobenzyl (PFB) bromide in the biological sample directly or after dilution with phosphate buffered saline, extraction of the reaction products with toluene and quantification in 1-μl aliquots of the toluene extract by selected-ion monitoring of m/z 112 for d(0)-Crea-PFB and m/z 115 for d(3)-Crea-PFB in the electron-capture negative-ion chemical ionization mode. The limit of detection of the method is 100 amol of creatinine. In an inter-laboratory study on urine samples from 100 healthy subjects, the GC-MS method was used to test the reliability of currently used Jaffé, enzymatic and HPLC assays in clinical and occupational studies. The results of the inter-laboratory study indicate that all three tested methods allow for satisfactory quantification of creatinine in human urine. The GC-MS method is suitable for use as a reference method for urinary creatinine in humans. In serum, creatine was found to contribute to creatinine up to 20% when measured by the present GC-MS method. The application of the GC-MS method can be extended to other biological samples such as saliva.
Exact decoupling of the Dirac Hamiltonian. I. General theory
The Journal of Chemical Physics, 2004
Exact decoupling of positive- and negative-energy states in relativistic quantum chemistry is dis... more Exact decoupling of positive- and negative-energy states in relativistic quantum chemistry is discussed in the framework of unitary transformation techniques. The obscure situation that each scheme of decoupling transformations relies on different, but very special parametrizations of the employed unitary matrices is critically analyzed. By applying the most general power series ansatz for the parametrization of the unitary matrices it is shown that all transformation protocols for decoupling the Dirac Hamiltonian have necessarily to start with an initial free-particle Foldy–Wouthuysen step. The purely numerical iteration scheme applying X-operator techniques to the Barysz–Sadlej–Snijders (BSS) Hamiltonian is compared to the analytical schemes of the Foldy–Wouthuysen (FW) and Douglas–Kroll–Hess (DKH) approaches. Relying on an illegal 1/c expansion of the Dirac Hamiltonian around the nonrelativistic limit, any higher-order FW transformation is in principle ill defined and doomed to f...
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Papers by Alexander Wolf