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A Reichert

Publications and source records attributed to A Reichert.

At least 37 records · Page 2Linked to original sources
PubMed1996

The Intracellular pH of Clostridium paradoxum, an Anaerobic, Alkaliphilic, and Thermophilic Bacterium.

When the extracellular pH was increased from 7.6 to 9.8, Clostridium paradoxum, a novel alkalithermophile, increased its pH gradient across the cell membrane ((Delta)pH, pH(infin) - pH(infout)) by as much as 1.3 U. At higher pH values (>10.0), the (Delta)pH and membrane potential ((Delta)(psi)) eventually declined, and the intracellular pH increased significantly. Growth ceased when the extracellular pH was greater than 10.2 and the intracellular pH increased to above 9.8. The membrane potential increased to 110 (plusmn) 8.6 mV at pH 9.1, but the total proton motive force ((Delta)p) declined from about 65 mV at pH 7.6 to 25 mV at pH 9.8. Between the extracellular pH of 8.0 and 10.3, the intracellular ATP concentration was around 1 mM and decreased at lower and higher pH values concomitantly with a decrease in growth rate.

Journal Article↗
PubMed1995

Retrovirus-like particles released from the human breast cancer cell line T47-D display type B- and C-related endogenous retroviral sequences.

The human mammary carcinoma cell line T47-D releases retrovirus-like particles of type B morphology in a steroid-dependent manner (I. Keydar, T. Ohno, R. Nayak, R. Sweet, F. Simoni, F. Weiss, S. Karby, R. Mesa-Tejada, and S. Spiegelman, Proc. Natl. Acad. Sci. USA 81:4188-4192, 1984). Furthermore, reverse transcriptase (RT) activity is found to be associated with particle preparations. Using a set of degenerate primers derived from a conserved region of retroviral pol genes, we repeatedly amplified three different retroviral sequences (MLN, FRD, and FTD) from purified T47-D particles in several RT-PCR experiments. Screening of a human genomic library and Southern blot analysis revealed that these sequences are of endogenous origin. ERV-MLN represents a multicopy family of human endogenous retroviral elements (HERVs) with two closely related copies and up to 20 more distantly related members. In contrast, ERV-FRD and ERV-FTD comprise only one copy and five to seven related elements per haploid human genome. DNA sequence analysis of the proviral pol region of ERV-MLN revealed an uninterrupted stretch of 241 amino acids that shows 65% identity with the RT of the type B-related HERV designated HERV-K10. ERV-FRD and ERV-FTD are defective type C-related HERVs. The pol gene of ERV-FRD displays a nucleotide homology of 54% to the gibbon ape leukemia virus, and the pol gene of ERV-FTD is about 67% homologous to members of the RTVL-I family of HERVs. Our results thus indicate that the retroviral particles released by the breast cancer cell line T47-D are probably generated by complementation of several endogenous proviruses and can package retroviral transcripts of different origins.

Amino Acid Sequence↗
PubMed1995

[Priming effects in picture problems: preliminary solutions].

Two experiments explored whether picture puzzles are an adequate instrument to investigate implicit memory for pictorial information. During the testing phase, the subjects had to identify hidden figures in picture puzzles. In a preceding learning phase, the priming conditions were varied systematically. In the first experiment, some subjects had to solve picture puzzles in the learning phase, whereas others made esthetic judgments (global processing) or estimated the number of triangles in the picture puzzles (local processing). In the second experiment, the subjects inspected copies of figures that were hidden at testing, modified versions of these figures, or their names in the learning phase. In the first experiment, the subjects of the different encoding conditions showed comparable priming effects. Picture puzzles that had already been processed or seen during learning were solved more often than new ones. Interview data revealed that subjects in the local or global processing conditions did not identify hidden figures at encoding. Furthermore, these subjects could not discriminate between old and new picture puzzles in a final explicit test of recognition. Thus, nonconscious storage of perceptual information that is not semantically interpreted may be sufficient to evoke priming effects. In the second experiment, the subjects in the different encoding conditions showed reliable priming effects, too. The presentation of the duplicates at encoding produced the greatest amount of priming. Effects of verbal priming, however, indicate that the solution of picture puzzles is not based solely on perceptual information. Depending on the priming conditions at learning, the solution of picture puzzles may be based primarily on data-driven processing or may be guided more heavily by conceptual information. It is concluded that perceptual, lexical, and/or conceptual information can contribute to the solution of picture puzzles.

Adult↗
PubMed1994

The sulfoxide of thymosin beta 4 almost lacks the polymerization-inhibiting capacity for actin.

Thymosin beta 4 (T beta 4), a peptide of 43 amino acids, binds to actin monomers and inhibits filament formation. In preparations of T beta 4 from bovine lung tissue, the peptide is accompanied by a derivative in which the methionine residue in position 6 is replaced by its sulfoxide. T beta 4 sulfoxide inhibits actin polymerization to an extent approximately 20-times less than T beta 4. While an equimolar amount of T beta 4 prevented actin polymerization almost completely, polymerization with the corresponding amount of the sulfoxide proceeded in a manner similar to that of pure actin, except for a slight retardation. We showed that the decrease in the inhibitory activity is reflected by a 20-times lower affinity to actin. Interestingly, under non-polymerizing conditions, the affinity of T beta 4 sulfoxide for actin is as high as that of T beta 4 (approximately 1 microM). In accordance with this, no differences were found between T beta 4 and the sulfoxide in cross-linking experiments with the monomer, where both forms of the peptide yielded similar amounts of a 47-kDa band representing conjugates of actin and beta-thymosin, as proved by Western-blotting analysis. Likewise, both, T beta 4 and the sulfoxide retarded the exchange of G-actin-bound nucleotide to similar extents. Although the sulfoxide is presumably a product of autoxidation, it is attractive to speculate that oxidation of the methionine residue in T beta 4 may represent a regulatory switch for starting filament formation in non-muscle cells.

Actins↗
PubMed1994

Polymerization of actin from the thymosin beta 4 complex initiated by the addition of actin nuclei, nuclei stabilizing agents or myosin S1.

Thymosin beta 4 forms a 1:1 complex with actin and thereby prevents polymerization. Rapid formation of filaments from this complex was observed, however, when actin trimers were added. Polymerization can likewise be initiated by the addition of one equivalent of phalloidin or, less effectively, cytochalasin B. Since both toxins, which reportedly support nucleation, have similar effects as the covalently linked actin trimers, it appears that the formation of filaments from the actin-thymosin beta 4 complex depends on the availability of stable actin nuclei. Remarkably, rapid polymerization was also observed if small amounts of myosin S1 were added, suggesting that also myosin, a protein functionally connected with polymeric actin, can serve as a nucleation center. Considering the existence of thymosin beta 4 and related peptides in numerous mammalian tissues, our data suggest that spontaneous formation of microfilaments in non-muscle cells may be regulated at the level of nucleation. Uncontrolled polymerization induced by the formation of phalloidin-stabilized nuclei may explain the acute toxic effects of phalloidin in hepatocytes.

Actins↗
PubMed1994

[Early changes in the hip joint following epiphysiolysis of the femoral head. Results of an MRT study].

With the aim of detecting patients at risk of developing coxarthritis, 34 patients were investigated prospectively by MRI 6-14 years after epiphysiolysis for slipped capital femoral head. In particular, cartilage changes were analysed by gradient-echo sequences. In 40% of the hip joints investigated cartilaginous lesions were present, detectable as irregularity and flattening of contour and more rarely as changes in signal intensity. In contrast, only 18% of the radiographs available revealed any pathology. When pelvic X-rays are normal or reveal slight sclerosis, cartilaginous lesions on MRI are considered early signs of coxarthrosis. This combination was seen especially often in patients with a primarily high angle of dislocation and in those who needed treatment by reposition or osteotomy. Only in 8 of the 17 hip joints showing sclerosis on conventional radiograms, sclerosis was also diagnosed by MRI, possibly because of partial volume and susceptibility effects at high field strength. Even with limited spatial resolution, cartilage examination is warranted in young patients in whom early osteoarthritis can be expected.

Adult↗
PubMed1993

Use of bimanyl actin derivative (TMB-actin) for studying complexation of beta-thymosins. Inhibition of actin polymerization by thymosin beta 9.

By reacting trimethylammoniobromobimane bromide (TMB bromide) with rabbit muscle actin, a fluorescent reporter group was linked to cysteine at position 374. Fluorescence of TMB-actin decreased significantly on addition of thymosin beta 4 (T beta 4), a peptide of 43 amino acid residues reported to bind to monomeric actin and to prevent filament formation. Based on this effect, we determined the KD value of the thymosin beta 4 complex as 0.8 microM, a value that is in agreement with previous determinations. In addition to the main compound thymosin beta 4, bovine tissue contains a related peptide, thymosin beta 9 (T beta 9), which has 41 amino acid residues and ca. 75% sequence homology. In the present study we show for the first time that T beta 9, similar to T beta 4, forms a 1:1 complex with monomeric actin, and hereby inhibits actin polymerization. With a KD value of 1.1 microM the affinity of T beta 9 is in the same range as that of T beta 4, suggesting that T beta 9, like T beta 4, contributes to maintaining the pool of monomeric actin in bovine non-muscle cells. Further proof of the interaction of T beta 9 with actin was provided by native PAGE, where the complex showed the reported higher mobility, as well as by crosslinking experiments. Using different crosslinking reagents, like water-soluble carbodiimide (EDC), m-maleimidobenzoyl-N-hydroxysuccinimidate (MBS), and disuccinimidylsuberate (DSS), we were able to produce conjugates of 47 kDa. In one of these (from MBS) both actin and T beta 9 could be identified by immunoblotting. When, in the MBS crosslinking experiments, native actin was replaced with (374-NEM)-actin, the 47 kDa band was not seen, indicating that Cys-374 takes part in the thiol-specific crosslinking reaction. This suggests that part of the binding site of T beta 9 must be located close to the carboxy-terminus.

Actins↗
PubMed1993

Transplacental induction of pancreas tumors in hamsters by ethanol and the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

Epidemiological studies suggest that smoking during pregnancy and passive exposure of children to cigarette smoke may increase the cancer risk in children and young adults. We have previously shown that the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is an active transplacental carcinogen in Syrian golden hamsters when administered by s.c. injections to pregnant females. The majority of tumors in the offspring developed in the respiratory tract. Since in smoking women the respiratory tract is the portal of entry of tobacco-related carcinogens, including NNK, we have investigated the transplacental effects of NNK given by intratracheal instillation to pregnant hamsters. The modulating effect of ethanol on the transplacental carcinogenicity of NNK in this system was also investigated because smoking and consumption of alcoholic beverages are observed in pregnant women. Our data show that exposure to NNK via the maternal respiratory tract causes a similar tumor incidence in the offspring as the s.c. route of administration. Ethanol greatly enhanced the carcinogenic response to NNK, and up to 60% of the offspring exposed in utero to ethanol and NNK developed tumors of the exocrine pancreas.

Animals↗
PubMed1992

The stability and functional properties of proteoliposomes mixed with dextran derivatives bearing hydrophobic anchor groups.

Liposomes composed of Escherichia coli phospholipid were coated with polysaccharides bearing hydrophobic palmitoyl anchors. The effect on the stability of liposomes without or with integral membrane proteins was investigated. A high concentration of hydrophobized dextrans protected the liposomes against detergent degradation, decreased the fluidity of the membranes, prevented fusion of the liposomes and enhanced their stability. Proteoliposomes containing beef heart cytochrome-c oxidase and the lactose transport carrier of E. coli were similarly affected by coating with the dextrans. Under these conditions both membrane proteins were still active. Long-term stability of the coated liposomes was obtained only in the absence of the integral membrane proteins.

Animals↗
PubMed1992

Spontaneous domain formation of phospholipase A2 at interfaces: fluorescence microscopy of the interaction of phospholipase A2 with mixed monolayers of lecithin, lysolecithin and fatty acid.

Fluorescence microscopy has recently been proven to be an ideal tool to investigate the specific interaction of phospholipase A2 with oriented substrate monolayers. Using a dual labeling technique, it could be shown that phospholipase A2 can specifically attack and hydrolyze solid analogous L-alpha-DPPC domains. After a critical extent of monolayer hydrolysis the enzyme itself starts to aggregate forming regular shaped protein domains (Grainger et al. (1990) Biochim. Biophys. Acta 1023, 365-379). In order to confirm that the existence of hydrolysis products in the monolayer is necessary for the observed aggregation of phospholipase A2, mixed monolayers of D- and L-alpha-DPPC, L-alpha-lysoPPC and palmitic acid in different ratios were examined. The phase behavior and the interaction of these films with phospholipase A2 were directly visualized with an epifluorescence microscope. Above a certain critical concentration of lysolecithin and palmitic acid in the monolayer, compression of these mixed films leads to phase separation and formation of mixed domains of unknown composition. Their high negative charge density is evidenced by preferential binding of a cationic dye to these phase-separated areas. Introduction of fluorescence-labeled phospholipase A2 underneath these mixed domains results in rapid binding of the protein to the domains without visible hydrolytic activity, regardless of whether the L-form or the D-form of the DPPC were used. In binary mixtures, only those with DPPC/palmitic acid show formation of phase-separated areas which can be specifically targeted by phospholipase A2 leading to a rapid formation (within 2 min) of protein domains. Experiments with pyrenedecanoic acid containing monolayers give the first direct evidence that acid is located above the enzyme domains. These results show that a locally high negative charge density of the phase-separated domains is one of the prerequisites for the binding of phospholipase A2. In addition, however, small amounts of D- or L-alpha-DPPC headgroups within the domains of the monolayer seem to be necessary for recognition followed by fast binding of the protein to the domains. This is confirmed by experiments with mixed monolayers of diacetylene carboxylic acid and D-alpha-DPPC. The acid--immiscible with lecithin--forms well defined pure acid domains in the monolayer. While the cationic dye can be docked rapidly to these phase separated areas, no preferential enzyme binding and thus no protein domain formation below these acid domains can be induced.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

Small unilamellar liposomes from mixed natural and polymeric phospholipids: stability and susceptibility to phospholipase A2.

The concept of the uncorkable liposome composed of phase-separated mixtures of a polymerized phospholipid and an enzymically digestible phospholipid has been investigated, using small unilamellar vesicles composed of mixtures of (polymerized) dienoylphosphatidylcholine (DENPC) and dimyristoylphosphatidylcholine (DMPC). Mixed liposomes, even those containing only 10% DENPC, were much more stable than DMPC liposomes, as indicated by the release of entrapped [3H]inulin or [14C]glucose. DMPC liposomes released entrapped solute on exposure to phospholipase A2, whereas mixed vesicles were resistant. The results are compared with those of an earlier study on monolayers of similar compositions. It is concluded that the liposomes, like the monolayers, are phase-mixed, and that uncorkable liposomes cannot be constructed from the phospholipid mixture employed. It is proposed that, until further experimental evidence is produced, the enzymatically uncorkable liposome must be regarded as a theoretical construct.

Carbon Radioisotopes↗
PubMed1990

Hydrolytic action of phospholipase A2 in monolayers in the phase transition region: direct observation of enzyme domain formation using fluorescence microscopy.

Phospholipase A2, a ubiquitous lipolytic enzyme highly active in the hydrolysis of organized phospholipid substrates, has been characterized optically in its action against a variety of phospholipid monolayers using fluorescence microscopy. By labeling the enzyme with a fluorescent marker and introducing it into the subphase of a Langmuir film balance, the hydrolysis of lipid monolayers in their liquid-solid phase transition region could be directly observed with the assistance of an epifluorescence microscope. Visual observation of hydrolysis of different phospholipid monolayers in the phase transition region in real-time could differentiate various mechanisms of hydrolytic action against lipid solid phase domains. DPPC solid phase domains were specifically targeted by phospholipase A2 and were observed to be hydrolyzed in a manner consistent with localized packing density differences. DPPE lipid domain hydrolysis showed no such preferential phospholipase A2 response but did demonstrate a preference for solid/lipid interfaces. DMPC solid lipid domains were also hydrolyzed to create large circular areas in the monolayer cleared of solid phase lipid domains. In all cases, after critical extents of monolayer hydrolysis in the phase transition region, highly stabile, organized domains of enzyme of regular sizes and morphologies were consistently seen to form in the monolayers. Enzyme domain formation was entirely dependent upon hydrolytic activity in the monolayer phase transition region and was not witnessed otherwise.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Mixed monolayers of natural and polymeric phospholipids: structural characterization by physical and enzymatic methods.

This study has focused on physical characterization and enzymatic hydrolysis of mixed monolayers of a natural phospholipid substrate and a polymerizable phospholipid analogue. Such a mixed system presents the possibility to stabilize model biomembranes, vary the molecular environment within the layer through polymerization and simultaneously examine these influences on monolayer structure. Phospholipase A2 was used here as a sensitive probe of the molecular environment within these mixed, polymerizable monolayers to complement information obtained from isotherm and isobar data. The results clearly show a strong influence of molecular environment on phospholipase A2 activity, even if differences in the physical state of mixed monolayers are not detectable with isotherm and isobar measurements. Physical characterization indicated that both monomeric and polymeric mixed monolayers were phase-mixed. Enzyme hydrolysis, however, showed large differences in the ability of the enzyme to selectively hydrolyze the natural phosphatidylcholine component from the monomeric as opposed to the polymeric mixtures. This demonstrates a high sensitivity of phospholipase A2 to distinguish subtle differences in molecular arrangement within mixed monolayers on a molecular level.

Chemical Phenomena↗
PubMed1990

[Immunofluorescence in the diagnosis of acute bacterial meningitis].

We evaluated immunofluorescence techniques to investigate the presence of S pneumoniae, N meningitidis, H influenzae types a and b and L monocytogenes in 85 samples of CSF fluid: 60 were taken from patients suffering meningitis and 25 from a control group. Results were compared to conventional bacteriologic methods. There were no false positive results in the control group. In patients with meningitis, 28 were positive by both methods. Nine additional patients were positive only to immunofluorescence which allowed identification of S pneumoniae in 6, N meningitidis in 2 and H influenzae in 1. 37 samples were positive by immunofluorescence and 28 of them were positive to conventional bacteriology. There was only 1 case of Group B streptococcus identified by bacteriology which was not diagnosed by immunofluorescence. Thus, immunofluorescence increases the ability to make a bacteriologic diagnosis in patients with meningitis.

Acute Disease↗
PubMed1989

Antitumoral activity of a xanthate compound. I. Cytotoxicity studies with neoplastic cell lines in vitro.

Xanthate derivatives were shown previously to display antitumor activity against transformed fibroblasts and lymphoma cells in combination with monocarboxylic acids [1]. Various malignant cell lines of human origin were treated in vitro to explore the range of antitumoral activity of the compounds. The combination of tricyclodecan-9-yl-xanthogenate (D 609) with undecanoic acid (C11) exerted dose dependent cytotoxic and antiproliferative effects on cell lines both from solid tumors (glioblastomas, colon-carcinomas) and hematological diseases (lymphomas, CML/BC). Additionally, the combination of D 609/C11 was able to kill both methotrexate- and adriamycin-resistant L 1210 and S 180 cells, indicating that there is no cross-resistance for these drugs and D 609/C11 in vitro.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1989

Antitumoral activity of a xanthate compound. II. Therapeutic studies in murine leukemia and tumor models in vivo.

The combinations of tricyclodecan-9-yl-xanthogenate (D 609) with undecanoic acid (C11) and D 609 with myristic acid (C14) were tested in 3 rodent tumor models in vivo. D 609 in combination with C11 or C14 did not show antitumoral efficacy in 3-Lewis lung carcinoma (3-LL) growing in syngeneic C57BL6-mice (primary tumor and metastasis) or in WEHI-3B myelomonocytic leukemia growing in Balb/c mice, when given in a dose range lower than the lethal dose for 10% of the treated animals (LD10). In L 1210 mouse lymphoid leukemia growing in CD2F1 mice the combination of D 609/C11 given intraperitoneally in a concentration of 100 mg/kg for more than 1 day effected a significant difference in the survival curves between the control and therapeutic groups in 1 out of 2 experiments. In conclusion, the treatment schedules of D 609/C11 or D 609/C14 used in this study has not revealed significant therapeutic effects in mouse tumors or leukemias in vivo.

Animals↗