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T Kaiser

Publications and source records attributed to T Kaiser.

36 records · Page 2Linked to original sources
PubMed2000

Methylenetetrahydrofolate reductase polymorphisms are not a risk factor for pre-eclampsia/eclampsia in Australian women.

In European and Japanese but not in Australian, American, and South African women, the C677T methylenetetrahydrofolate reductase (MTHFR) polymorphism has been reported to be a genetic risk factor pre-eclampsia/eclampsia (PE/E). The recently described A1298C MTHFR gene polymorphism also results in reduced MTHFR enzyme activity, although to a lesser extent than the previously described C677T polymorphism. Heterozygotes for both polymorphisms are reported to have an even lower MTHFR enzymatic activity than seen in homozygotes for the C677T genotype. In this current study we determined the allele frequency of the A1298C MTHFR gene polymorphism in an Australian population and examined this polymorphism alone and in combination with the C677T MTHFR polymorphism for an association with PE/E. Neither the A1298C polymorphism alone nor a combination of both polymorphisms showed an association with PE/E in our population of Australian women.

Alleles↗
PubMed2000

Prothrombin G20210A mutation: is it associated with pre-eclampsia?

OBJECTIVE: A strong independent association between the prothrombin G20210A gene mutation and pre-eclampsia has been reported in an Italian population. This result was not confirmed in a subsequent study in a Dutch population. The objective of this study was to further test the hypothesis that the prothrombin G20210A mutation is associated with pre-eclampsia/eclampsia. METHODS: Seventeen eclamptics and 67 pre-eclamptics were recruited from 34 multicase Australian/New Zealand families. An additional 105 unrelated pre-eclamptic/eclamptic women and 119 parous women were recruited as controls. RESULTS: The overall incidence for the prothrombin G20210A gene mutation in the pre-eclamptic group was 3.6% (95% CI 1.2-8.2%) which was not significantly different from the control group 2.5% (95% CI 0.5-7.2%) (p = 0.73, OR 1.44, 95% CI 0.34-6.17). CONCLUSION: This study provides little evidence of a significant relationship between the prothrombin G20210A gene mutation and pre-eclampsia. Based on our results, we do not recommend testing for the prothrombin G20210A mutation in the routine investigation of women with pre-eclampsia.

Adult↗
PubMed1999

Solid-phase synthesis, isolation and analysis of a mouse protein, the macrophage migration inhibitory factor.

Murine macrophage migration inhibitory factor (mMIF) is an Mr 12,500 protein composed of all natural amino acid residues. Using the fluorenylmethoxycarbonyl chemistry for solid-phase peptide synthesis (SPPS) under special conditions, a stepwise approach was very successful leading to a crude product in unexpected high purity. After RP-HPLC isolation, a little mass difference of -12 u was determined for the received protein by matrix-assisted laser desorption ionization MS and ion spray MS and the failure sequence [Ser15]-mMIF identified by Edman degradation. The total solid-phase synthesis was repeated in the stepwise manner under the same conditions leading to the expected mMIF protein in high purity, which was confirmed by different analytical methods. Our results shows the reproducibility of our SPPS approaches to proteins and point out the importance of high-resolution mass spectrometry for a rapid and accurate analysis of such biopolymers.

Amino Acid Sequence↗
PubMed1998

Selective uptake of cholesteryl esters from high-density lipoprotein-derived LpA-I and LpA-I:A-II particles by hepatic cells in culture.

Selective uptake of high-density lipoprotein (HDL)-associated cholesteryl esters (CE), i.e. lipid uptake independent of HDL particle uptake, delivers CE to the liver and steroidogenic tissues in vivo and in vitro. From human plasma HDL, two major subpopulations of particles can be isolated: one contains both apolipoprotein (apo) A-I and apo A-II (designated LpA-I:A-II) as dominant protein components, whereas in the other apo A-II is absent (LpA-I). In this study, selective CE uptake from LpA-I and LpA-I:A-II by cultured cells was investigated. LpA-I and LpA-I:A-II were isolated by immunoaffinity chromatography from human plasma high-density lipoprotein3 (HDL3, d = 1.125-1.21 g/ml) and both particles were radiolabeled in the protein (125I) as well as in the CE moiety ([3H]cholesteryl oleyl ether ([3H]CEt)). Several control experiments validated the labeling methodology applied. To investigate selective CE uptake, human Hep G2 hepatoma cells, human hepatocytes in primary culture and human skin fibroblasts were incubated in medium containing doubly radiolabeled LpA-I or LpA-I:A-II particles. Thereafter cellular tracer content was determined. For each cell type the rate of apparent lipoprotein particle uptake according to the lipid tracer ([3H]CEt) was in substantial excess over that due to the protein tracer (125I), demonstrating selective CE uptake from LpA-I as well as from LpA-I:A-II. This difference in uptake between [3H]CEt and 125I, i.e. the rate of apparent selective CE uptake, was significantly higher for LpA-I compared to LpA-I:A-II, and this was dose- as well as time-dependent. Thus in human hepatic cell and fibroblasts, CE are selectively taken up to a higher extent from LpA-I compared to LpA-I:A-II. These results may suggest that LpA-I particles of the human plasma HDL fraction may be those lipoproteins which more efficiently deliver CE to the liver via the selective uptake pathway whereas LpA-I:A-II may play a less important role.

Apolipoprotein A-I↗
PubMed1998

Hepatic lipase mediates an increase in selective uptake of high-density lipoprotein-associated cholesteryl esters by human Hep 3B hepatoma cells in culture.

Selective uptake of high-density lipoprotein- (HDL-) associated cholesteryl esters (CE), i.e. lipid uptake independent from particle uptake, delivers CE to the liver and steroidogenic tissues in vivo. In vitro, besides hepatocytes and steroidogenic cells many other cell types selectively take up HDL CE. Hepatic lipase (HL) stimulates the internalisation of apoprotein (apo) B-containing lipoproteins by hepatocytes independent from lipolysis. In this study the role of HL in the hepatic metabolism of apo A-I-containing lipoproteins, i.e. HDL, was investigated. HDL3 (d = 1.125-1.21 g/ml) was radiolabeled in its protein (125I) and in its CE moiety ([3H]cholesteryl oleyl ether, ([3H]CEt)). HL originated from tissue culture media of hepatoma cells and from post-heparin plasma. Human Hep 3B hepatoma cells incubated in medium containing radiolabeled HDL3. In the absence of HL, the rate of apparent HDL3 particle uptake according to the lipid tracer ([3H]CEt) was in most cases in approximately 10-fold excess on that due to the protein label (125I), indicating selective CE uptake from HDL3. Addition of HL to these incubations increased the cellular uptake of [3H]CEt and of 125I from HDL3 and quantitatively the most prominent effect was an up to approximately 2.5-fold stimulation of apparent selective CE uptake ([3H]CEt-125I). This increase in selective CE uptake was observed in the presence of tetrahydrolipstatin, an inhibitor of the catalytically active site of HL, suggesting that this HL effect is independent from lipolysis. HL binds to cell surface heparan sulfate proteoglycans. To explore the role of these molecules for the HL effect on selective CE uptake, hepatoma cells were depleted of proteoglycans or Chinese hamster ovary (CHO) cells deficient in proteoglycan synthesis were used. Proteoglycan-deficiency reduced the HL-mediated increase in selective uptake by more than 80%. To investigate if low-density lipoprotein (LDL) receptors or the LDL receptor-related protein (LRP) are involved in the HL effect on selective CE uptake, murine embryonic fibroblasts (MEF) were used which are deficient in these receptors; alternatively, monensin, an inhibitor of endocytosis was present in the medium of Hep 3B cells during the uptake assay for labeled HDL3. These experiments yielded no evidence for a role of LDL receptors or LRP in the HL-mediated increase in selective CE uptake. In summary, HL mediates an increase in HDL3 selective CE uptake by human Hep 3B hepatoma cells. This HL effect is independent from lipolysis and independent from LRP and LDL receptors. However this HL effect is susceptible to cell surface proteoglycan deficiency. The potential physiologic implication is that HL modifies HDL selective CE uptake by the liver in vivo and such an effect could play a role in reverse cholesterol transport.

Animals↗
PubMed1998

Lipoprotein lipase mediates an increase in the selective uptake of high density lipoprotein-associated cholesteryl esters by hepatic cells in culture.

In this study the effect of lipoprotein lipase (LPL) on the selective uptake of high density lipoprotein (HDL) cholesteryl esters (CE) by hepatic cells was investigated. Human HDL3 (d 1.125-1.21 g/ml) was radiolabeled with 125I in the protein moiety and with 3H in the CE moiety. LPL was prepared from bovine milk. Human hepatocytes in primary culture and human Hep3B hepatoma cells were incubated in medium containing doubly radiolabeled HDL3 with or without LPL. Without LPL, apparent HDL3 particle uptake according to the lipid tracer (3H) was in excess of that due to the protein label (125I) indicating selective CE uptake from HDL3. Addition of LPL increased selective CE uptake up to 7-fold. This stimulation of HDL3 selective CE uptake was independent of the lipolytic activity of LPL as suggested by several experimental approaches. Cell surface heparan sulfate proteoglycan deficiency decreased the LPL-mediated increase in selective CE uptake suggesting an important role for these molecules. In low density lipoprotein (LDL) receptor- or LDL receptor-related protein-(LRP)-deficient cells, LPL increased selective CE uptake as it did in normal cells yielding no evidence that these receptors play a role in the LPL effect on selective CE uptake. In summary, lipoprotein lipase increases the selective uptake of high density lipoprotein-associated cholesteryl ester by hepatic cells in culture. This effect is dependent on cell surface heparan sulfate proteoglycans but independent of lipolysis and of endocytosis mediated by low density lipoprotein receptor-related or low density lipoprotein receptors.

Animals↗
PubMed1997

Vicinal thiols are involved in inositol 1,2,3,5,6-pentakisphosphate 5-phosphatase activity from fetal calf thymus.

Inositol 1,2,3,5,6-pentakisphosphate (Ins(1,2,3,5,6)P5) 5-phosphatase present in fetal calf thymus has been partially purified. This enzyme was inhibited dose-dependently by different thiol modifiers like N-ethylmaleimide (NEM), p-chloromercuribenzene sulfonate (PCMBS), diamide, and phenylarsine oxide (PAO). The inhibition by PCMBS and diamide was protected by preincubation with dithiothreitol (DTT) and the phosphatase substrate, Ins(1,2,3,5,6)P5. Diamide, a compound that specifically modifies vicinal thiol groups, also blocked the 5-phosphatase dose-dependently. Specificity of this blockade was proven by using dimercaptopropanol (DMP), a compound known to protect vicinal thiol groups. DMP prevented the enzyme from inhibition by diamide. These data suggest that vicinal thiols are involved in Ins(1,2,3,5,6)P5 5-phosphatase activity.

Animals↗
PubMed1997

[Electromyography of the sphincter vesicae externus muscle. Technique, indications and outcome].

Electrophysiological examinations provide important findings for the clarification of urogenital dysfunctions. A routine electromyogram (EMG) of the external anal sphincter is used together with stimulation of the pudendal nerve to determine lesions of the somatomotor tract. An alternative is the electromyographical examination of the external vesical sphincter. This special method requires more time and sufficient experience. We see an indication for EMG of the voluntary vesical sphincter in urogenital dysfunctions that cannot be sufficiently differentiated with EMG of the external anal sphincter and also in disturbances that selectively affect the external vesical sphincter.

Electromyography↗
PubMed1996

Behavioral vigilance following infusions of 192 IgG-saporin into the basal forebrain: selectivity of the behavioral impairment and relation to cortical AChE-positive fiber density.

Rats were trained in a previously validated behavioral vigilance task that required them to detect visual signals of variable length and to discriminate signal from nonsignal events. Baseline performance was characterized by a signal length-dependent ability to score hits, a decline in hits over time, and a correct rejection rate of approximately 70%. After the rats reached criterion performance in this task, the immunotoxin 192 IgG-saporin or its vehicle was infused into the area of the nucleus basalis/substantia innominata of the basal forebrain. Postoperative performance in lesioned rats was characterized by a decrease in their ability to detect signals while their ability to correctly reject nonsignals remained unaffected. The effect of the lesion did not recover in the course of over 180 sessions of postlesion testing. The overall performance of the rats correlated with acetylcholinesterase (AChE)-positive fiber density in all cortical areas measured except the cingulate and pyriform cortex. These findings help to elucidate the nature of the attentional impairments resulting from the loss of cortical cholinergic inputs.

Acetylcholinesterase↗
PubMed1996

[A case of HELLP syndrome complicated by acute renal failure and acute respiratory failure].

We present a case of HELLP (haemolysis, elevated liver enzymes, low platelets) syndrome that developed post partum in 31 year old woman. It was initially misdiagnosed as acute cholecystitis. The disease was complicated with acute renal failure and acute respiratory failure. Admission to the intensive therapy unit became necessary; patient required haemodialysis and short lasting mechanical ventilation. The outcome of described case was nevertheless good.

Acute Kidney Injury↗
PubMed1995

Selective uptake of low-density lipoprotein-associated cholesteryl esters by human fibroblasts, human HepG2 hepatoma cells and J774 macrophages in culture.

High-density lipoprotein-(HDL) associated cholesteryl esters (CE) are taken up by hepatic and extrahepatic cells at a higher rate than HDL apolipoproteins. This selective uptake of HDL CE is independent from HDL particle uptake. For low-density lipoprotein (LDL), receptor-mediated endocytosis by cells is well established. In this study, the question was addressed if LDL-associated CE are also taken up by cells independently from LDL particles, i.e., selectively. Human LDL (d = 1.02-1.05 g/ml) was doubly radiolabeled with intracellularly trapped tracers: [125I]Tyramine-Cellobiose ([125I]TC) traced apolipoprotein B, [3H]cholesteryl oleyl ether ([3H]CEt) traced CE. The uptake of doubly radiolabeled LDL by normal and LDL receptor-negative human skin fibroblasts, human HepG2 hepatoma cells and murine J774 macrophages was investigated. Each cell type took up LDL particles as indicated by [125I]TC. However, in fibroblasts, HepG2 cells and J774 macrophages the rate of uptake for LDL-associated [3H]CEt was greater than that according to [125I]TC. These results indicate that extrahepatic and hepatic cells selectively take up LDL CE and this uptake is independent from LDL receptor-mediated endocytosis. Loading cells with cholesterol down-regulated selective uptake of LDL CE. In summary, human skin fibroblasts, human HepG2 cells and murine J774 macrophages selectively take up LDL CE, i.e., CE are taken up independently from LDL particles.

Animals↗
PubMed1995

Promoter elements of the mustard CHS1 gene are sufficient for light regulation in transgenic plants.

The expression of chalcone synthase (CHS) genes, which encode the first enzyme of the flavonoid pathway, is under developmental control as well as affected by external stimuli such as light. Varying fragments of the 1 kb upstream region of the CHS1 gene from white mustard (Sinapis alba L.) were fused to the GUS-coding region, and the light-regulated expression of these constructs was analysed in transgenic Arabidopsis and tobacco plants. Studies performed with Arabidopsis seedlings indicate the presence of two elements within the CHS1 promoter mediating light responses via different photoreceptors. One element, located about 150 bp upstream of the transcription start site, is homologous to Unit 1 of the parsley CHS gene, the second, far more upstream element carries sequences similar to Unit 2 of the same gene. Detailed studies on Unit 1-driven expression indicate that this element transfers the expression characteristics of the original gene to both Arabidopsis and tobacco. Although the expression characteristics of Unit 1 are indistinguishable from those of the full-length promoter within the same species, we observed differences in mustard CHS promoter regulation between Arabidopsis and tobacco plants transgenic for the identical construct. The difference in photoreceptor usage by the same promoter element in different transgenic species (Unit 1 from mustard in Arabidopsis vs. tobacco) was also observed for different but homologous promoter elements in the same transgenic species (Unit 1 from mustard and parsley in tobacco). We therefore conclude that the same promoter and even the same promoter element (Unit 1) can mediate different spatial patterns of expression and modes of light regulation in different transgenic species.

Acyltransferases↗
PubMed1995

Cis-acting elements of the CHS1 gene from white mustard controlling promoter activity and spatial patterns of expression.

Chalcone synthase (CHS) catalyses the first regulatory step in the branch pathway of phenylpropanoid biosynthesis specific for synthesis of ubiquitous flavonoid pigments and UV protectants. External stimuli such as stress, light and wounding induce CHS expression that is both tissue-specific and under developmental control. In order to identify cis-acting elements involved in organ and tissue specifity, we fused varying parts of the CHS1 promoter of white mustard (Sinapis alba L.) to the GUS-coding region and analysed the expression of these constructs in stably transformed Arabidopsis plants. Two different stages of development were examined, seedlings as an early stage and flowers as the final stage of development. In seedlings, the full-length promoter showed expression in all organs except the hypocotyl; in flowers expression could be observed in all whorls. Unit 1 of the mustard CHS1 promoter, an element conserved in several CHS genes, which has been recently identified as a light responsive element, is able to mediate a tissue-specific expression pattern similar to that obtained with the full-length promoter in seedlings as well as in flowers. Other elements enhance or repress expression in combination with Unit 1, or mediate defined spatial expression independently of Unit 1. One such element, located between -907 and -655, directs expression similar to that of the full-length promoter in flowers but not in seedlings and differs therefore in function to Unit 1. Our data suggest a dominant regulation of CHS1 expression by Unit 1. Other elements within this promoter might interact with Unit 1 or confer a subset of spatial expression patterns when Unit 1 is deleted.

Acyltransferases↗
PubMed1990

Binding of aromatic amines to the rat hepatic Ah receptor in vitro and in vivo and to the 8S and 4S estrogen receptor of rat uterus and rat liver.

Studies on structurally related aromatic amines with different carcinogenic properties have shown that 2-acetylaminofluorene (2-AAF) and 2-acetylaminophenanthrene (AAP) inhibit the binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin to the Ah receptor in vitro. The apparent inhibitor constants (Ki) are 2.3 microM for 2-AAF and 2.7 microM for AAP. In contrast, 4-acetylaminofluorene, an isomer of 2-AAF, and trans-4-acetylaminostilbene do not bind to the rat hepatic cytosolic Ah receptor. Pretreating female Wistar rats with 2-AAF or AAP leads to the induction of the P-450 isoenzymes that are under the control of the Ah receptor. Ornithine decarboxylase activity is induced by all aromatic amines tested irrespective of their Ah receptor affinity. The aromatic amines used as model compounds do not inhibit the binding of 17-beta-estradiol to the 8S and 4S estrogen receptor of rat uterus or rat liver in a competition assay analyzed using sucrose density gradient centrifugation. On the other hand, the aromatic amines bind to varying extents to another estrogen-binding protein of rat liver whose function and identity is still unknown. Our study demonstrates that structurally related aromatic amines in their unmetabolized form interact differentially with a cellular target protein, the Ah receptor, in vitro as well as in vivo. However, a relationship between these effects and the postulated promoting properties of 2-AAF remains to be established.

Amines↗
PubMedDate not supplied

Concepts for the syntheses of biotinylated steroids. Part I: testosterone derivatives as immunochemical probes.

We describe synthetic strategies for the biotinylation of testosterone (T) at positions 3, 7alpha, 17alpha, and 19. These T probes are able to mimic ligand binding and may provide for a better understanding of the biospecific interaction with steroid-binding proteins such as the androgen receptor, anti-steroid antibodies, or steroid-binding serum globulins. For the 7alpha- and 17alpha-derivatives, biotinyl-N-hydroxy-succinimide esters with different types of spacer chains were used. The 3-biotin hydrazone derivative was produced using N-(epsilon-biotinyl)-caproyl hydrazide, whereas for the 19-biotinylation, a biotinyl-1-N-diamino-3, 6-dioxaoctane-amide was applied. Key reaction for the biotinylation at position 3 is the oximation of the 3-oxo function. The 17alpha-position is accessible by the reaction of the 3-protected 4-androsten-17-epoxide with oxygen in the beta-position, followed by nucleophilic ring opening with cyanide which provides the 17alpha-cyanomethyl derivative. The key step is the regioselective ketal protection of the 3-oxo function of androst-4-ene-3,17-dione using a stannoxane catalyst. An alternative pathway for the insertion of biotin at the 19-position was established by the synthesis of 17beta-hydroxy-androst-4-en-3-one-19-yl carboxymethyl ether. After activation by the carbodiimide method, the compound reacts with aminoterminal biotin derivatives. The copper(I)-catalyzed 1,6 Michael addition of 17-acetoxy-6,7-dehydro-T leads to 7alpha-derivatives by use of omega-silyl protected hydroxylalkyl-modified Grignard reagents. A functional group interconversion using the Staudinger reaction transforms the azide function into a primary omega-amino group. The absolute configurations of the different biotinylated derivatives were investigated by (1)H NMR studies. For the 7alpha-biotinylated T series, additionally, an X-ray analysis proved the axial position of the spacer group. This results in a vertical orientation of the biotin moiety toward the alpha-face of the planar tetracyclic backbone. Thus, a negligible alteration of the original structure of the upper beta-face offers the feasibility of applying the 7alpha-derivatives as optimal immunochemical tracers in competitive immunoassays. Biotinylated T derivatives should be also suitable for ligand-binding studies to the androgen receptor or to sex hormone-binding globulin.

Biotinylation↗
PubMedDate not supplied

Concepts for the syntheses of biotinylated steroids. Part II: 17beta-estradiol derivatives as immunochemical probes.

Biotinylated 17beta-estradiol (E2) derivatives are helpful probes for a better understanding of biospecific E2 interactions with steroid-binding proteins such as the estrogen receptor and anti-steroid antibodies. We describe synthetic strategies for the biotinylation of E2 toward the 3, 6alpha, and 7alpha positions using biotinyl-N-hydroxysuccinimide esters with different spacers, varying in structure and chain length. Key reaction for biotinylation at the 3 position is the regioselective ether formation of the phenolate E2 anion with a linker mesylate without protecting the 17beta-hydroxyl group. The 6alpha position is accessible via a 3,17beta protected 6alpha-hydroxy E2, prepared by stereospecific sodium borohydride reduction of 6-oxo E2. Direct cyanoethylation of the alcohol followed by reduction to the amine allows the biotinylation to 6alpha-O-coupled cyanoethyloxy linker E2 derivatives. Alternatively, 6alpha-O-coupled cyanoalkyloxy polyether linker E2 probes are obtained by a Williamson ether synthesis of the alcohol precursor with omega-t-butyl-dimethylsilyloxy-5-oxa-nonylmesylate. Cyanoethylation of the desilylated compound and further reduction of the nitrile led to the terminal amine. Reductive amination of the 3, 17beta acetylated 6-oxo E2 compound with 6-cyanoethyloxyhexyl ammonium acetate yields in a mixture of 6alpha/beta-N-alkylated E2 nitriles. The epimers are separated by reversed-phase HPLC and the 6alpha-compound subsequently reduced to the terminal amine. The 7alpha-biotinylated E2 compound is derived from 7alpha-(11'-undecyl-N-methyl-N-butylamide) E2, which is already known from literature. Subsequently, the 3 and 17beta positions are protected, and the amide is reduced to the 7alpha-(11'-undecanol) compound. Further cyanoethylation and reduction led to the 11'-amino-ethyloxyundecyl E2. Using (1)H NMR analysis, it could be shown that the biotin moiety of the biotinylated 6alpha- and 7alpha-E2 derivatives has an axial position which results in a vertical orientation of the substituent toward the alpha-face of the planar tetracyclic backbone. Thus, a negligible alteration of the original structure of the upper beta-face offers the feasibility of applying the 6alpha- and 7alpha-derivatives as optimal tracers in competitive immunoassays.

Biotin↗
PubMedDate not supplied

Human speech development for an implantable artificial larynx.

An electromagnetic artificial larynx was implanted in two volunteer laryngectomees. Both patients were able to communicate well, but the voice quality still needed improving. Therefore, in this investigation, listener judgments were obtained of 22 different sound sources with a view to incorporating the preferred speech sound in a new version of the device. Electroglottograms were used as sound sources in a speech synthesizer and sentences were produced with different voice qualities for judgmental tests. The results of the listening tests showed a distinct preference for waveforms corresponding to a long completely open phase, a very brief completely closed phase, and an abrupt closing gesture. The optimum acoustic characteristics for the device will be used by electrical engineers to manufacture a new version of the artificial larynx with an improved voice quality.

Electrodiagnosis↗