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L Winkler

Publications and source records attributed to L Winkler.

At least 19 recordsLinked to original sources
PubMed2006

On the self-association potential of transmembrane tight junction proteins.

Tight junctions seal intercellular clefts via membrane-related strands, hence, maintaining important organ functions. We investigated the self-association of strand-forming transmembrane tight junction proteins. The regulatory tight junction protein occludin was differently tagged and cotransfected in eucaryotic cells. These occludins colocalized within the plasma membrane of the same cell, coprecipitated and exhibited fluorescence resonance energy transfer. Differently tagged strand-forming claudin-5 also colocalized in the plasma membrane of the same cell and showed fluorescence resonance energy transfer. This demonstrates self-association in intact cells both of occludin and claudin-5 in one plasma membrane. In search of dimerizing regions of occludin, dimerization of its cytosolic C-terminal coiledcoil domain was identified. In claudin-5, the second extracellular loop was detected as a dimer. Since the transmembrane junctional adhesion molecule also is known to dimerize, the assumption that homodimerization of transmembrane tight junction proteins may serve as a common structural feature in tight junction assembly is supported.

Animals↗
PubMed2003

Immunohistochemical expression of inhibin-alpha in human endometrium and the in vitro secretion of inhibin, estradiol and cortisol in cultured human endometrial glandular cells.

BACKGROUND: Inhibins are multipotent dimeric glycoproteins, composed of an alpha-subunit and one of two possible beta-subunits (betaA or betaB). Aims of this study were (a): the immunohistochemical characterisation of normal human endometrium for the inhibin-alpha subunit; (b) the assessment of the secretion and metabolism of inhibin, E2 and cortisol; (c) the evaluation of any relationship between these three substances in cell culture medium of isolated and cultivated normal human endometrial glandular cells. MATERIALS AND METHODS: Samples of human endometrium were obtained from 34 premenopausal patients. Nineteen endometrial specimen (proliferative [PP] n=8; early secretory [ES] n=7; late secretory phase [LS] n=4) were brought into cell culture. Fifteen endometrial specimen (PP n=5; ES n=5; LS n=5) were paraffin-fixed and used for the immunohistochemical analysis for inhibin-alpha. Stromal and epithelial cells were separated by collagenase digestions, filtrations, sedimentations and Ficoll-gradient centrifugation. E2 and cortisol were measured with radioimmunoassay (RIA) and inhibin with enzyme-immunoassay (EIA). Statistical analysis was performed with the non-parametric Mann-Whitney rank-sum test and linear regression analysis. RESULTS: Inhibin-alpha showed a weak (positive) expression during proliferative phase, which increased significantly as the menstrual cycle continued. In secretory glands the mean inhibin concentration was higher than that from proliferative samples. A significant correlation was observed between inhibin and E2 (p<0.001) as well as cortisol and inhibin (p<0.0001) in glands from proliferative phase. Between inhibin and E2 (p<0.05) as well as inhibin and cortisol (p<0.002) a significant correlation in early secretory glands was also noted. In late secretory phase inhibin and E2 (r2=0.78650; p<0.0001), inhibin and cortisol (r2=0.58326; p<0.001) and E2 and cortisol (r2=0.52880; p<0.001) showed a significant correlation. DISCUSSION: In conclusion, we found a cyclical expression of inhibin-alpha subunit in the endometrium demonstrated by immunohistochemical means. A higher in vitro secretion of inhibin from secretory glands was also observed. In addition, a significant correlation between inhibin with E2 and cortisol in PP and ES glands and a significant correlation between inhibin, E2 and cortisol in LS glands could also be demonstrated. We conclude that inhibin can be associated with E2 and cortisol metabolism, playing an important role in paracrine/autocrine mechanisms in the endometrium and possibly exerting its function through cortisol and E2. The cortisol concentration also correlates with E2, suggesting a link between these steroids in the endometrial function. The correlation of inhibin, E2 and cortisol suggest complex autocrine/ paracrine mechanisms in human endometrial glands, modulated and controlled by all these three substances.

Adult↗
PubMed2003

[Investigations on isolation, purification and cultivation of human endometrial cells and on the in vitro inhibin expression in glandular epithelial cells].

The separate in vitro cultivation of isolated and purified human endometrial glands and stromal cells seems to be the most attractive experimental way of studying the endometrial function on cellular level. In this paper a new method has been described to establish monolayer cultures of isolated endometrial stromal and epithelial cell populations. After a first collagenase digestion, stromal and epithelial cells were separated by filtration. The glandular epithelial cells were further purified with two collagenase digestion steps, filtration, a differential sedimentation at unity gravity and a Ficoll gradient centrifugation. Stromal cells were isolated with the use of erylyse-buffer, filtration and differential sedimentation at unity gravity. A significant higher inhibin production was observed during late secretory compared to proliferative and early secretory phase. Therefore, glandular epithelial cells maintain in vitro their initial differentiation. The higher inhibin concentration during secretory phase implicates a substantial role in endometrial function and maturation. Therefore, inhibin could be used as a marker of endometrial differentiation. Experiments on isolated glandular epithelial cells should be performed within two weeks. The method described here allows the propagation in vitro of separate endometrium cell types which can be used to study endometrial function as well as implantation mechanisms.

Cell Culture Techniques↗
PubMed2002

A reporter-cell assay for the detection of BMP-2 immobilized on porous and nonporous materials.

Human recombinant bone morphogenetic protein-2 (rhBMP-2) immobilized on the surface of metal implants can facilitate osseointegration. Here, we describe a cell reporter assay useful for quantifying small amounts of immobilized rhBMP-2 on various materials. The peptide was dotted and heat-fixed on titanium, 316L stainless steel, nitrocellulose, or glass, and its distribution was monitored by in situ biotinylation followed by detection with the avidin-biotin method. Bioactivity of rhBMP-2 was demonstrated by means of a confluent layer of osteoblastic MC3T3-E1 cells that evenly covered rhBMP-2-free and rhBMP-2-loaded surface areas, as shown with epifluorescence microscopy of calcein acetoxymethyl (AM)-loaded cells. Expression of osteocalcin, fibronectin, actin, and vimentin increased where cells were located on rhBMP-2 dotted areas, but the signal:noise ratio was too low to bioassay the peptide. However, local pronounced expression of alkaline phosphatase was used to quantify BMP-2 in the range of 5-80 ng/dot by means of a cytochemical color reaction for alkaline phosphatase and image analysis of resulting dots. The lower detection limit was in the order nitrocellulose > glass > titanium > 316L steel. We conclude that the cell reporter assay is useful to assess biological activity of rhBMP-2 even after immobilization on three-dimensional implant materials.

Alkaline Phosphatase↗
PubMed2002

[Initiation of oral anticoagulant treatment: comparison between different dosage regimens of warfarin and phenprocoumon].

A high "loading dosage" is often given during initiation of oral anticoagulant treatment in order to reach sufficient anticoagulation within short time. Increased bleeding risk as well as a transient prothrombotic tendency are complications of this treatment schedule. The aim of our study was to find proper dosage regimens of phenprocoumon and warfarin allowing initiation of oral anticoagulant treatment in a short time. For 50% of the patients 7.5 mg warfarin daily resulted in stable INR values within 4 days. Patients receiving higher (10 mg) or lower (5 mg) daily dosages of warfarin or 6 or 9 mg phenprocoumon daily during the first days of therapy reached the therapeutic range significantly later. Furthermore, no significant differences of prothrombin fragment F 1+2 were observed, indicating that no enhanced thrombin formation occurred. Thus, initiation of oral anticoagulant treatment using 7.5 mg warfarin daily is a simple and safe dosage regimen.

Administration, Oral↗
PubMed2000

Sulphur-containing "perfumes" attract flower-visiting bats.

We tested the attractiveness of individual scent compounds of bat-pollinated flowers to their pollinators, small flower-visiting bats of the genus Glossophaga (Phyllostomidae). Twenty compounds belonging to four different chemical substance classes were tested, both in the laboratory and in the field. In the laboratory, the bats (Glossophaga soricina) approached odour sources spontaneously and without preceding experience. Without ever receiving any reward they preferred the scent of a sulphur-containing compound, dimethyl disulphide, to several other odour components emitted by bat-pollinated flowers, and to scentless controls. In the field, at La Selva station in the tropical lowland rain forest of Costa Rica, G. commissarisi were attracted by two sulphur-containing compounds, dimethyl disulphide and 2,4-dithiapentane, to visit artificial flowers filled with sugar water. Thus, in nectarivorous bats the sense of smell obviously plays an important role in searching for and localising food sources, and even single components of the scent bouquets of bat-pollinated flowers are attractive. The preference for sulphur-containing odours seems to be innate.

Animals↗
PubMed1997

Visualization of a covalent intermediate between microsomal epoxide hydrolase, but not cholesterol epoxide hydrolase, and their substrates.

Mammalian soluble and microsomal epoxide hydrolases have been proposed to belong to the family of alpha/beta-hydrolase-fold enzymes. These enzymes hydrolyse their substrates by a catalytic triad, with the first step of the enzymatic reaction being the formation of a covalent enzyme-substrate ester. In the present paper, we describe the direct visualization of the ester formation between rat microsomal epoxide hydrolase and its substrate. Microsomal epoxide hydrolase was precipitated with acetone after brief incubation with [1-(14)C]epoxystearic acid. After denaturing SDS gel electrophoresis the protein-bound radioactivity was detected by fluorography. Pure epoxide hydrolase and crude microsomes showed a single radioactive signal of the expected molecular mass that could be suppressed by inclusion of the competitive inhibitor 1,1,1-trichloropropene oxide in the incubation mixture. In a similar manner, 4-fluorochalcone-oxide-sensitive binding of epoxystearic acid to rat soluble epoxide hydrolase could be demonstrated in rat liver cytosol. Under similar conditions, no covalent binding of [26-(14)C]cholesterol-5alpha,6alpha-epoxide to microsomal proteins or solubilized fractions tenfold enriched in cholesterol epoxide hydrolase activity could be observed. Our data provide definitive proof for the formation of an enzyme-substrate-ester intermediate formed in the course of epoxide hydrolysis by microsomal epoxide hydrolase, show no formation of a covalent intermediate between cholesterol epoxide hydrolase and its substrate under the same conditions as those under which an intermediate was shown for both microsomal and soluble epoxide hydrolases and therefore indicate that the cholesterol epoxide hydrolase apparently does not act by a similar mechanism and is probably not structurally related to microsomal and soluble epoxide hydrolases.

Amino Acid Sequence↗
PubMed1997

[40 years breast carcinoma treatment in the Neubrandenburg region.Can an increase in prognostically more favorable stages be detected?].

The data of clinical presentation for women suffering from breast carcinoma were analysed for a period of 4 decades retrospectively. The authors have found a significant decrease in the duration of the history and an increase of early stages of the breast carcinoma. This increase was caused by the introduction of mammography. The mammography is the most important method for the diagnosis of breast carcinoma in asymptomatic women.

Breast Neoplasms↗
PubMed1993

Hybrid hybridomas producing bispecific antibodies to CEA and peroxidase isolated by a combination of HAT medium selection and fluorescence activated cell sorting.

A combination of fluorescence-activated cell sorting and HAT medium selection has been used to establish bispecific antibody (biAbs)-producing hybrid hybridomas. For this purpose hypoxanthine-guanine phosphoribosyl transferase (HGPRT)-deficient mutants were isolated from a hybridoma line (D11-DG2) producing anti-CEA antibodies by 8-azaguanine treatment. The resulting HAT-sensitive hybrid cells were stained with the fluorescence marker tetramethyl rhodamine isothiocyanate (TRITC) and fused by polyethylene glycol (PEG) with HAT-non-sensitive unstained hybrid cells producing antibodies to horseradish peroxidase (POD). Fluorescent fused hybrid hybridomas as well as non-fused stained anti-CEA cells were separated from the unstained anti-POD cells using a fluorescent activated cell sorter (FACS). Finally, non-fused enzyme-deficient anti-CEA cells were eliminated by cultivation in HAT selection medium which permits only an outgrowth of HAT-resistant hybrid hybridoma cells containing the genes for producing both antibodies.

Animals↗
PubMed1993

Growth and pubertal development in nephropathic cystinosis.

In a retrospective investigation growth and pubertal development were evaluated in 30 patients with nephropathic cystinosis. Growth was investigated during the stage of chronic renal insufficiency as well as after successful kidney transplantation and growth rates were related to kidney function. Pubertal development was evaluated in 17 patients between 12 and 25 years of age. Prepubertal growth rates were stable in a range between -2 and -3 height velocity SDS as long as glomerular filtration rate was above 20ml/min per 1.73m2. A decrease in glomerular filtration rate below this threshold was followed by further decrease in height velocity. After kidney transplantation a significant catch-up growth was seen if immunosuppression was performed with cyclosporine A and low dose prednisolone. This did not occur if conventional therapy with azathioprine and high-dose prednisolone was used. Onset of puberty was delayed in all patients. Gonadotropin and oestradiol levels in female patients showed normal fluctuations according to ovulatory cycles. In male patients after puberty there was an increase in gonadotropin levels above the normal range for adult men while testosterone levels remained in the low normal range. These results indicate that adult men with nephropathic cystinosis may develop hypergonadotropic hypogonadism.

Adolescent↗
PubMed1993

Low-density lipoprotein catabolism does not respond to estrogen in the fetal and newborn rat.

The elimination of native and methylated low-density lipoprotein (LDL) from serum and the effect of estradiol on the serum LDL-apoB pool, the uptake of homologous [125I]-LDL into liver and adrenals, and the fractional catabolic rate (FCR) of [125I]-LDL was studied in fetal (22nd day of gestation), newborn (15th day postpartum), and adult rats. In fetal rats the receptor-mediated LDL decay accounted only for 47%, whereas in adults it was calculated to 65%. In the latter, estrogen caused (1) a diminution of the serum LDL-apoB pool by 85%; (2) an enhancement of the LDL uptake into the liver and the adrenals by 5- and 10-fold, respectively, and (3) an acceleration of the [125I]-LDL decay in the serum with a rise of the FCR by 3-fold. In contrast, neither the LDL pool and uptake nor the LDL elimination (FCR) did respond to estrogen in fetal and newborn rats. In summary, the LDL catabolism of the rat is insensitive towards estrogen in the late gestational period and during the first 2 weeks of postnatal life [3].

Adrenal Glands↗
PubMed1993

[Physical and mental development of children with congenital hypothyroidism].

69 children with congenital hypothyroidism, who were detected by neonatal screening in Lower Saxony, were reevaluated 1-12 years after diagnosis. They had been treated either by regional children's hospitals, local pediatricians or general practitioners. Substitution of thyroid hormone had started for the majority between day 7 and 14, for 17%, however, only later. Symptoms suggestive of hypothyroidism at birth were observed in 35 children, but only 3 cases were correctly diagnosed before the result of the screening was known. Further diagnostic tests to elucidate the cause of congenital hypothyroidism had been performed in 33 children. In 36 cases the etiology remained undiagnosed at the evaluation. Hormone therapy had been administered continuously in all cases. The somatic development of all children was normal. Bone age at the time of diagnosis was retarded in more than 50%, later it became normal in most cases. The psychomotor and intellectual development was satisfactory as assessed by psychometric tests. The mean value of the Intelligence Quotients in the children older than six years was 96.3. 5 children of this age group had an IQ below 85 and only one child had an IQ of more than 115. In the younger group the results were similar, but children younger than 4 years showed deficiencies in speech development. In summary, the somatic development of the re-examined children with congenital hypothyroidism was normal, but the psychomotor and intellectual development was only subnormal in some cases. It is therefore suggested that children with congenital hypothyroidism should be closely followed by experienced pediatricians, especially in the early years of life.

Age Determination by Skeleton↗
PubMed1992

The visceral yolk sac--an important site of synthesis and secretion of apolipoprotein B containing lipoproteins in the feto-placental unit of the rat.

Rat fetuses exhibit a high serum LDL concentration at term. Delivery caused a marked decrease of the LDL apolipoprotein (apo) B concentration independent of whether this occurred on days 21, 22 or 23 of gestation. The interruption of the yolk sac circulation by a ligature in situ for 6 h led to the same alterations of the LDL-apo B concentration as Caesarean section. Immunoelectronmicroscopic studies provided evidence that the epithelial cells of the visceral yolk sac exhibited electron dense LDL-sized and apo B containing particles which were localized over the compartments of the Golgi complexes, endoplasmatic reticulum, secretory vesicles and intercellular spaces, but not over the cell nuclei, mitochondria or lysosomes. ApoB containing LDL-sized particles could be obtained by ultracentrifugation from the disrupted material of the microsomal fraction of yolk sac homogenates. Isolated segments of the yolk sac membranes were capable to secrete apoB containing lipoproteins floating in the d less than 1.020 g/ml as well as in the d = 1.020-1.064 g/ml fraction with a 10-fold higher amount of apoB in the higher density class. Incorporation experiments with [35S] methionine gave evidence that these lipoproteins were at least partially provided with newly synthesized apoB predominantly found in the LDL fraction. The size of the negatively stained particles in the d = 1.020-1.064 g/ml fraction secreted from yolk sac segments corresponded to that of LDL from fetal rat serum. In contrast their acylglycerol content was significantly higher, whereas the percentage contribution of total cholesterol and protein was markedly reduced in comparison with serum LDL of the fetus. In summary, biochemical and ultrastructural studies provide clear cut evidence that the rat yolk sac is able to synthesize and to deliver apo B containing lipoproteins in the density ranges of VLDL, IDL and particular of LDL thus contributing to the supply of serum lipoproteins in the rat fetus. By recalculation of recent tracer kinetic data (Plonné et al. (1990) J. Lipid Res. 31, 747) using a mathematical step function model it was possible to assess the contribution of the rat yolk sac to the LDL influx into the fetal serum.

Animals↗
PubMed1992

Increase in plasma total and lipoprotein cholesterol during incubation of whole blood samples at 37 degrees C--influence of LCAT inhibitors.

Incubation of whole blood samples at 37 degrees C caused a time-dependent increase in plasma cholesterol concentrations. In samples from 40 fasting healthy males, plasma cholesterol rose by 13.6 +/- 3% during 24 h (P less than 0.001). Changes in cholesterol concentrations were found in both the HDL fraction and the VLDL/LDL fraction. The increase in lipoprotein cholesterol concentrations correlated positively with the initial levels of HDL cholesterol and apo A-I; and with the original levels of VLDL/LDL cholesterol, apo B and triglycerides. The increase in plasma total cholesterol was not related to the HDL cholesterol and apo A-I concentrations. It was more pronounced in samples with elevated plasma concentrations of total cholesterol, VLDL/LDL cholesterol, apo B and triglycerides. The elevation in plasma total cholesterol resulted from an increase in cholesteryl esters, whereas free cholesterol decreased. After LCAT inhibition no changes in total, free and esterified cholesterol were observed. Therefore, increase in plasma cholesterol seems to represent a LCAT-dependent cholesterol transport out of blood cells.

Adult↗
PubMed1992

Synthesis, secretion and immunoelectron microscopic demonstration of apolipoprotein B-containing lipoprotein particles in the visceral rat yolk sac.

Electron microscopic investigations on the involvement of the fetal membranes of the rat (visceral yolk sac) in the lipid metabolism revealed the occurrence of lipoprotein-sized particles located in cisternal Golgi stacks, Golgi vesicles and secretory vesicles of the cells of the visceral yolk sac epithelium as well as in distended areas of the intercellular space between adjacent epithelial cells. Application of the protein A-gold technique with specific anti-apoB antiserum resulted in a specific location of immunogold both over the different compartments of the lipoprotein pathway (RER, Golgi complex, secretory vesicles) as well as over the distended intercellular spaces, thus confirming these particles to be lipoproteins in nature. Isolated visceral epithelial cells prepared by a tryptic digestion method exhibited some ultrastructural alterations, such as a loss of apical brush border, a change from columnar to spherical cell shape, a decrease in phagolysosomes, but an increase in autophagosomal structures after 6 h incubation at a vitality rate of at least 85%. Within this period the epithelial cells secreted measurable amounts of apoB-containing lipoproteins into the medium floating in the density classes d less than 1.006 g/ml, d = 1.006-1.020 g/ml and d = 1.020-1.064 g/ml. The production of the lipoproteins was partly inhibited by cycloheximide indicating the secretion of particles with performed as well as newly synthesized apoB. Negative staining of the particles revealed an average diameter of 34 nm of VLDL, 31 nm of IDL and 24 nm of LDL. In summary, our studies demonstrate that in the feto-placental unit of the rat the fetal membranes are capable of synthesizing and secreting lipoproteins. The cells of the visceral yolk sac epithelium were shown to be the producers of apoB-containing particles.

Animals↗