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M Schrader

Publications and source records attributed to M Schrader.

At least 19 recordsLinked to original sources
PubMed1998

Apical plasma membrane proteins and endolyn-78 travel through a subapical compartment in polarized WIF-B hepatocytes.

We studied basolateral-to-apical transcytosis of three classes of apical plasma membrane (PM) proteins in polarized hepatic WIF-B cells and then compared it to the endocytic trafficking of basolaterally recycling membrane proteins. We used antibodies to label the basolateral cohort of proteins at the surface of living cells and then followed their trafficking at 37 degreesC by indirect immunofluorescence. The apical PM proteins aminopeptidase N, 5'nucleotidase, and the polymeric IgA receptor were efficiently transcytosed. Delivery to the apical PM was confirmed by microinjection of secondary antibodies into the bile canalicular-like space and by EM studies. Before acquiring their apical steady-state distribution, the trafficked antibodies accumulated in a subapical compartment, which had a unique tubulovesicular appearance by EM. In contrast, antibodies to the receptors for asialoglycoproteins and mannose-6-phosphate or to the lysosomal membrane protein, lgp120, distributed to endosomes or lysosomes, respectively, without accumulating in the subapical area. However, the route taken by the endosomal/lysosomal protein endolyn-78 partially resembled the transcytotic pathway, since anti-endolyn-78 antibodies were found in a subapical compartment before delivery to lysosomes. Our results suggest that in WIF-B cells, transcytotic molecules pass through a subapical compartment that functions as a second sorting site for a subset of basolaterally endocytosed membrane proteins reaching this compartment.

5'-Nucleotidase↗
PubMed1998

Effects of angiotensin II on bone cells in vitro.

Other than its known effects on the cardiovascular system, angiotensin II (Ang II) stimulates cell growth in several cell types. In this study, we examined whether it also might affect bone cell metabolism. Ang II stimulated DNA and collagen synthesis and decreased alkaline phosphatase (AP) activity in bone cell populations derived from the periosteum of fetal rat calvariae. Similar effects of Ang II were observed on human adult bone cells obtained by collagenase digestion from trabecular bone. Clonal cell analysis, autoradiographic studies, and receptor subtype analysis suggested the presence of specific Ang II receptor subtype 1 (AT1) binding sites on AP+ osteoblastic precursor cells. Ang II had no direct effects on osteoblastic cells with a mature phenotype, but paracrine effects of Ang II on mature osteoblasts could be observed upon coculture with Ang II-responsive bone cell populations. Because Ang II is known to be locally generated by endothelial cells, Ang II might play an important role in coordinating capillary cell growth and osteoblastic bone formation during bone remodeling.

Angiotensin II↗
PubMed1998

Using social network and ethnographic tools to evaluate syphilis transmission.

BACKGROUND AND OBJECTIVES: Partner notification has been the cornerstone for the prevention and control of syphilis in the United States. This technique may not make full use of contextual data that an ethnographic and social network approach can offer. GOALS OF THE STUDY: The occasion of a syphilis outbreak among young people was used to investigate the applicability of a social network approach and to test the validity of several traditional approaches to syphilis epidemiology. STUDY DESIGN: An outbreak of syphilis was investigated by interviewing both infected and noninfected people, by directing resources based on network association, by creating and evaluating network diagrams as an aid to the epidemiologic process, and by including ethnographic observations as part of outbreak management. RESULTS: Diagrammatic display of network growth provided a useful alternative to the traditional epidemic curve. Case prevention was demonstrated by identifying uninfected people with multiple concurrent exposures. Concurrent, overlapping exposure in infected people rendered traditional "source" and "spread" criteria moot. CONCLUSIONS: The current discussions of partner notification may be informed by recognizing that it is a subset of a broader and potentially more powerful approach. This approach calls some basic tenets of syphilis epidemiology into question.

Adolescent↗
PubMed1997

Isolation and characterization of the circulating form of human endostatin.

Recently, fragments of extracellular proteins, including endostatin, were defined as a novel group of angiogenesis inhibitors. In this study, human plasma equivalent hemofiltrate was used as a source for the purification of high molecular weight peptides (10-20 kDa), and the isolation and identification of circulating human endostatin are described. The purification of this C-terminal fragment of collagen alpha1(XVIII) was guided by MALDI-MS and the exact molecular mass determined by ESI-MS was found to be 18 494 Da. N-terminal sequencing revealed the identity of this putative angiogenesis inhibitor and its close relation to mouse endostatin. The cysteine residues 1-3 and 2-4 in the molecule are linked by disulfide bridges. In vitro biological characterization of the native protein demonstrated no anti-proliferative activity on different endothelial cell types. These data indicate that human endostatin, which is a putative angiogenesis inhibitor, is present in the circulation.

Amino Acid Sequence↗
PubMed1997

The disulphide bond pattern of bitistatin, a disintegrin isolated from the venom of the viper Bitis arietans.

The disulphide bond pattern of the long disintegrin bitistatin (83 amino acids, 14 cysteines) was established using structural information gathered by amino acid analysis, N-terminal sequencing, and molecular mass determination of fragments isolated by reversed-phase HPLC after polypeptide degradation with trypsin and oxalic acid. A computer program was used to calculate all possible combinations of disulphide-bonded peptides matching the mass spectrometric data, and the output was filtered using compositional and sequence data. Disulphide bonds between cysteines 16-34, 18-29, 28-51, 42-48, 47-72, and 60-79 are conserved in medium-long disintegrins flavoridin and kistrin (70 amino acids, 12 cysteines), and the two cysteine residues at positions 5 and 24 found in bitistatin but not in other disintegrin molecules are disulphide-bridged. This linkage creates an extra, large loop, which, depending on whether the NMR structure of flavoridin or kistrin is used for modelling the structure of bitistatin, lies opposite or nearly parallel, respectively, to the biologically active RGD-containing loop.

Amino Acid Sequence↗
PubMed1997

Peptide bank generated by large-scale preparation of circulating human peptides.

Human hemofiltrate (HF) is a source for the purification of circulating regulatory peptides. HF is obtained in large quantities during treatment of patients suffering from chronic renal failure. We have developed a large-scale method for separating peptides from amounts up to 10,000 1 HF into 300 fractions in a standardized two-step procedure, employing cation-exchange separation, followed by reversed-phase chromatography. These fractions represent a peptide bank containing bioactive, desalted and lyophilized peptides of blood. Screening for and isolation of regulatory human peptides is simplified by using this peptide bank.

Chromatography, High Pressure Liquid↗
PubMed1997

Matrix-assisted laser desorption/ionisation mass spectrometry guided purification of human guanylin from blood ultrafiltrate.

The purification of the human peptide hormone guanylin 22-115 from blood ultrafiltrate (hemofiltrate, HF) was achieved using matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) as the assay system. Screening a peptide bank generated from 5000 1 HF guanylin 22-115 was detected by its molecular mass when adequate conditions for MALDI-MS analysis were chosen. The sensitivity was even better than of the established biological assay system. In addition, the susceptibility towards solvents and salts is strongly reduced. 1.2 mg of the peptide hormone was purified from 10% of the starting material.

Chromatography, High Pressure Liquid↗
PubMed1997

Effect of alterations of blood cholesterol levels on macrophages in the myocardium of New Zealand White rabbits.

We investigated the effect of alterations of blood cholesterol levels on macrophages (mphi) in the myocardium of New Zealand White (NZW) rabbits. Three groups of NZW rabbits were used: controls, rabbits fed a 0.5% cholesterol-enriched diet (CH-D) for 96 days, and rabbits fed a 0.5% CH-D for 96 days followed by normal chow for 4 months. Immunohistochemical analysis by mAbs directed against mphi (RAM-11) and Mn superoxide dismutase (MnSOD) were quantified by computer-assisted morphometry. Using cultured human and rabbit mphi, a cross-reaction of the human MnSOD mAbs was found as well as the predominant localization of MnSOD-immunoreactivity (IR) in mitochondria. In group 1, only a very few RAM-11-immunoreactive (ir) mphi occurred in the interstitial space of the myocardium. In group II blood cholesterol levels significantly increased in parallel with the numbers of mphi, which often contained lipid droplets (foam cells). Although blood cholesterol concentrations regressed about 10-fold in group III, mphi in the myocardium were found to be reduced only about 20%. Most mphi were also MnSOD-ir. In atherosclerotic coronary arteries RAM-11-IR was located in mphi and also extracellularly, whereas MnSOD-IR was found only in mphi. Drastically induced MnSOD in the mitochondria of mphi is suggested as an indicator of increased oxidative stress caused by in vitro conditions or by phagocytosis of low-density lipoprotein in vivo. Elevation of the cholesterol level leads to a long-term increase and its regression results in a delayed reduction of such mphi, which seem to play a key role in the atherogenesis of the coronary arteries as well.

Animals↗
PubMed1997

Time-resolved fluorescence spectroscopy and imaging of DNA labeled with DAPI and Hoechst 33342 using three-photon excitation.

We examined the fluorescence spectral properties of the DNA stains DAPI (4',6-diamidino-2-phenylindole, hydrochloride) and Hoechst 33342 (bis-benzimide, or 2,5'-bi'1H-benzimidazole2'-(4-ethoxyphenyl)-5-(4-methyl-1-piperazi nyl)) with two-photon (2h nu) and three-photon (3h nu) excitation using femtosecond pulses from a Ti:sapphire laser from 830 to 885 nm. The mode of excitation of DAPI bound to DNA changed from two-photon at 830 nm to three-photon at 885 nm. In contrast, Hoechst 33342 displayed only two-photon excitation from 830 to 885 nm. DAPI-DNA displayed the same emission spectra and decay times for 2h nu and 3h nu excitation. Hoechst 33342-DNA displayed the same intensity decay for excitation at 830 and 885 nm. Both probes displayed higher anisotropies for multiphoton excitation as compared to one-photon excitation with ultraviolet wavelengths, and DAPI-DNA displays a higher anisotropy for 3h nu at 885 nm than for 2h nu at 830 nm. We used 970-nm excitation of DAPI-stained chromosomes to obtain the first three-dimensional images with three-photon excitation. Three-photon excitation of DAPI-stained chromosomes at 970 nm was demonstrated by the power dependence in the fluorescence microscope.

Benzimidazoles↗
PubMed1997

Chemo-radiotherapy for locally advanced head and neck cancer--long-term results of a phase II trial.

The feasibility and effectiveness of a combined chemo-radiotherapy treatment modality for locally advanced head and neck cancer was tested in a phase II trial. Between 1990 and 1993, 74 patients (20 female/54 male) with head and neck cancer stage III (n = 12) and IV (n = 62) were treated with accelerated radiotherapy (72 Gy) and simultaneous chemotherapy (5-FU, folinic acid, mitomycin C). The median follow-up time was 43 months (1-72). Complete remission (CR) was absent in 76% (56/74) of patients and, after subsequent resection of residual lymph nodes, another 8 patients achieved CR. The cumulative local control rate was 72% and disease-specific survival rate was 59% at 4 years. Two patients died with treatment-related conditions (pancytopenia, larynx oedema). By multivariate analysis, only lymph node status was an independent parameter for local control (P = 0.04). This treatment was feasible and toxicity was not a treatment-limiting factor. As a consequence, a German multicentre phase III trial was initiated in 1995.

Adult↗
PubMed1997

Far-field fluorescence microscopy with three-dimensional resolution in the 100-nm range.

We report three-dimensional (3D) microscopy with nearly isotropic resolution in the lambda/5-lambda/10 range. Our approach combines 4PI-confocal two-photon fluorescence microscopy with image restoration. The 3D resolution is demonstrated with densely clustered beads as well as with F-actin fibers in mouse fibroblast cells. A comparison with unrestored two-photon confocal images reveals a total reduction of the uncertainty volume up to a factor of 15.

Animals↗
PubMed1997

Induction of mitochondrial manganese superoxide dismutase in macrophages by oxidized LDL: its relevance in atherosclerosis of humans and heritable hyperlipidemic rabbits.

The objective of the study was to analyze the intracellular antioxidative response of macrophages (Mphi) exposed to increased levels of low density lipoprotein (LDL). We studied manganese superoxide dismutase (MnSOD) and, in part, GSH in cultured human and rabbit Mphi, and in atheromatous arterial tissue of humans and heritable hyperlipidemic (HHL) rabbits. Incubation of human Mphi with oxidized-LDL (ox-LDL) resulted in an induction of MnSOD mRNA production as shown by RT-PCR. MnSOD immunoreactivity (IR) was found to be located in the mitochondria of Mphi. In HHL rabbits, MnSOD activity and GSH concentration were significantly increased in atherosclerotic intima compared to the media of the aorta, but significantly decreased (P<0.01) in larger plaques compared with smaller ones, resulting in a significant inverse correlation of MnSOD activity (r=-0.67, P<0.001) and GSH concentration (r=-0.57, P<0.01) with plaque size. Immunohistology of the atherosclerotic intima revealed MnSOD-IR in Mac-1 (CD 11b/CD 18)-immunoreactive (ir) Mphi of human arteries and, similarly, in RAM-11-ir Mphi of rabbit ones. The relation of MnSOD-ir Mphi decreased with plaque advancement, which is consistent with biochemical findings. Most MnSOD-ir Mphi in atherosclerotic plaques revealed TUNEL-positive nuclei, indicating DNA strand breaks, and p53-IR. We conclude that mitochondrial antioxidants such as MnSOD are induced in Mphi in vitro and in atherosclerotic arteries as a reply to increased mitochondrial oxidation. As normal consequences of an increased oxidative stress due to the exposure to ox-LDL nuclear DNA strand breaks occur, which are suggested to be a signal to increase p53 protein levels. Reactive oxygen species-mediated mitochondrial-dependent pathways are suggested as major contributing pathomechanisms to nuclear damage, which eventually may result in apoptosis. A common response to increased oxidative stress due to modified LDL is presumed in rabbit and human atherosclerotic plaques.

Animals↗
PubMed1997

[Arterial and neural supply of the skin of the palm. Surgical-anatomical findings in Dupuytren's contracture].

It has been reported that the skin of the palm is supplied by arteries receiving their blood from a radial, thenar, ulnar, or hypothenar arterial system. Interestingly, the middle of the palm has been described as hypovascularized, but detailed informations on number and distribution of blood vessels are not available. By surgical treatment of the Dupuytrens contracture we could show that preservation of the blood vessels and nerves supplying the skin leads to excellent postoperative results. However, our intraoperative observations do not correspond to the picture of a poorly vascularized region of skin in the middle of the hand. During surgical treatment we found between six and nine bundles consisting of one artery, at least one vene, and one nerve in each case. The bundles perforate the palmar aponeurosis through channels, and subaponeurotically a lot of them originate from further proximal than expected. This information should be taken into consideration during the exstirpation of the palmar aponeurosis.

Adult↗
PubMed1997

[Vertigo].

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Diagnosis, Differential↗
PubMed1996

Isoprenylation of the G protein gamma subunit is both necessary and sufficient for beta gamma dimer-mediated stimulation of phospholipase C.

We have previously shown that isoprenylation and/or additional post-translational processing of the G protein gamma 1 subunit carboxyl terminus is required for beta 1 gamma 1 subunit stimulation of phospholipase C-beta 2 (PLC beta 2) [Dietrich, A., Meister, M., Brazil, D., Camps, M., & Gierschik, P. (1994) Eur. J. Biochem. 219, 171-178]. To examine whether isoprenylation of the gamma 1 subunit alone is sufficient for beta 1 gamma 1-mediated PLC beta 2 stimulation or whether any of the two subsequent modifications, proteolytic removal of the carboxyl-terminal tripeptide and/or carboxylmethylation, is required for this effect, nonisoprenylated recombinant beta 1 gamma 1 dimers were produced in baculovirus-infected insect cells, purified to near homogeneity, and then isoprenylated in vitro using purified recombinant protein farnesyltransferase. Analysis of the beta 1 gamma 1 dimer after in vitro farnesylation by reversed phase high-performance liquid chromatography followed by delayed extraction matrix-assisted laser desorption/ionization mass spectrometry confirmed that the gamma 1 subunit was carboxyl-terminally farnesylated but not proteolyzed and carboxylmethylated. Functional reconstitution of in vitro-farnesylated beta 1 gamma 1 dimers with a recombinant PLC beta 2 isozyme revealed that farnesylation rendered recombinant nonisoprenylated beta 1 gamma 1 dimers capable of stimulating PLC beta 2 and that the degree of this stimulation was only approximately 45% lower for in vitro-farnesylated beta 1 gamma 1 dimers than for fully modified native beta 1 gamma 1 purified from bovine retinal rod outer segments. Taken together, these results suggest that isoprenylation of the gamma subunit is both necessary and sufficient for beta gamma dimer-mediated stimulation of phospholipase C.

Alkyl and Aryl Transferases↗