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T Maier

Publications and source records attributed to T Maier.

At least 55 records · Page 3Linked to original sources
PubMed1997

Differential attachment of oral treponemes to monolayers of epithelial cells.

This in vitro study describes the attachment properties of several oral treponemes to monolayers of epithelial cells and the effect of epithelial cell confluence on treponeme attachment. Four serotypes of Treponema denticola, Treponema scoliodontum, three subspecies of Treponema socranskii, and Treponema vincentii were tested with monolayers of epithelial cells of human and canine origin. Attachment of oral treponemes were compared to attachment by T. pallidum subsp. pallidum, and by the non-pathogen Treponema phagedenis. Results indicated that different serotypes of T. denticola had similar abilities to attach to epithelial cells. However, subspecies of T. socranskii differed in their ability to attach to epithelial cells. The proportion of epithelial cells susceptible to attachment by oral spirochetes was strongly related to the confluence level of the monolayer. In contrast, T. pallidum attached equally well to both epithelial cell lines at all confluence levels. T. phagedenis attached to < 1% of all epithelial cells. In general, attachment of oral treponemes to canine cells was lower than to human cells, suggesting species-specificity for adherence. Attachment of oral treponemes to epithelial cells may promote colonization of the periodontal pocket, as well as retention of treponeme colonies within plaque. The preference of oral treponemes to attach to cells of low confluence fields may translate in vivo to an increased ability to attach to cells which are actively dividing. Such cells are found in areas of repair, a common status within inflamed periodontal pockets. Furthermore, attachment of oral treponemes to epithelial cell barriers may promote or potentiate cytopathic processes.

Animals↗
PubMed1996

Generation of active [NiFe] hydrogenase in vitro from a nickel-free precursor form.

The maturation process of [NiFe] hydrogenases includes formation of the nickel metallocenter, proteolytic processing of the large subunit, and assembly with the other hydrogenase subunit(s). An in vitro system for the maturation of the large subunit (HycE) of hydrogenase 3 of Escherichia coli leading to an active enzyme was established. The system is based on extracts of an E. coli mutant lacking the nickel-specific transport system (nik). HycE was present in these extracts in the C-terminally extended precursor form devoid of nickel. Addition of nickel led to nickel incorporation and proteolytic processing of HycE. Under anaerobic conditions, hydrogenase 3 activity was subsequently generated. The maximal rate of the processing reaction was reached at a nickel concentration of 400 microM. The accessory proteins known to be involved in the maturation of HycE in vivo, namely HypB, HypC, HypD, HypE, HypF, and the protease HycI, are required for the in vitro reaction, since processing of HycE did not occur in extracts of double mutants affected in the nik system and in one of the accessory genes. Processing of HycE and generation of hydrogenase 3 activity were achieved in extracts of the nik- delta hycI mutant by addition of both nickel and purified HycI protease.

Bacterial Proteins↗
PubMed1996

Nickel incorporation into hydrogenase 3 from Escherichia coli requires the precursor form of the large subunit.

A mutant derivative of hycE, the gene for the large subunit of hydrogenase 3 from Escherichia coli, was constructed that lacks the 3'-terminal part encoding the C-terminal portion of the HycE polypeptide, which is proteolytically removed during maturation of the hydrogenase. The truncated gene was transferred to the in situ position on the chromosome. Although the mutant possessed HycE in its "mature" form, it was devoid of hydrogenase 3 activity. The activity was not restored by high nickel concentrations in the medium. The mutated HycE was not associated with detectable radioactivity when the strain was grown in the presence of 63Ni2+. These results indicate that the C-terminal extension in the precursor form of the large subunit keeps the protein in a conformation required for the coordination of the metal.

Base Sequence↗
PubMed1996

Analysis of the hydA locus of Escherichia coli: two genes (hydN and hypF) involved in formate and hydrogen metabolism.

The hydA locus of Escherichia coli is known to encode some function necessary for formation of hydrogenase activity. The locus contains two open reading frames, hydN and hypF. In this communication, an analysis of the regulation of these two genes and of the phenotype of respective mutants is presented, Both genes were expressed in a T7 promoter/polymerase system, yielding a 19-kDa (HydN) and a 81-kDa (HypF) protein. In-frame deletions were constructed for each gene and transferred to the chromosome by homologous recombination. The mutation in hydN led to a decrease of the activity of formate dehydrogenase H (FDH-H) in crude extracts, but the activity and maturation of hydrogenases were nearly unaffected. In contrast, a deletion in hypF resulted in the loss of hydrogenase activity and in the synthesis of the large subunits of the hydrogenase isoenzymes 1, 2 and 3 in the inactive precursor form. For hydrogenase 3, it was shown that this is due to a lack of incorporation of nickel into the large subunit. hydN and hypF are organised in an operon that is a member of the formate regulon. Transcription was shown to be dependent on sigma 54 and FhlA, and an FhlA-binding site upstream of hydN was identified. The sigma 54-dependent promoter shows a rare deviation from the consensus at positions -24/-12, namely GG/GA instead of GG/GC. In conclusion, the product of hydN appears to have some role in electron flow from or to FDH-H, and the product of hypF is connected with maturation of all three hydrogenases of E. coli.

Amino Acid Sequence↗
PubMed1995

GTP hydrolysis by HypB is essential for nickel insertion into hydrogenases of Escherichia coli.

The product of the hypB gene, which is required for the maturation of the three [NiFe]hydrogenases of Escherichia coli, is a member of the GTPase family and exhibits a low intrinsic GTPase activity. It was studied whether or not GTP hydrolysis by HypB is coupled to nickel insertion into hydrogenases and to maturation of hydrogenases. Mutations were introduced into the hypB gene at sites expected to code for amino acids involved in guanine-nucleotide binding. Lys117 of G-motif 1, as well as Asp241 of G-motif 4 were substituted by asparagine residues. The purified mutant HypB proteins showed strongly reduced, but still significant, GTPase activity. In the case of [D241N]HypB, the kcat/Km value was lowered by a factor of 85 and the specificity of the enzyme for GTP was apparently lost, with other nucleoside triphosphates including XTP becoming compatible substrates. The decrease in GTPase activity was even more pronounced for [K117N]HypB. To assess the functionality of these HypB proteins in vivo, the wild-type hypB gene in the chromosome of E. coli was replaced by the mutant alleles. The resulting mutant strains BKN117 and BDN241 were affected in hydrogen metabolism under fermentative conditions. BKN117 did not display hydrogenase activity due to a loss of nickel incorporation into the large subunit. BDN241 exhibited a reduction of hydrogenase activity by 44% and only a portion of the hydrogenase 3 large subunit was in the mature nickel-containing form. From these results, it is concluded that GTP hydrolysis catalysed by HypB is an integral process in nickel incorporation into hydrogenases.

Amino Acid Sequence↗
PubMed1995

Characterisation of a protease from Escherichia coli involved in hydrogenase maturation.

The large subunits of nickel-containing hydrogenases are synthesised in a precursor form which, after nickel incorporation, is processed by proteolytic cleavage at the C-terminal end. The protease involved in processing of HycE, the large subunit of hydrogenase 3 from Escherichia coli, was purified by three chromatographic steps to apparent homogeneity. Its gene was identified by using a hybridisation probe generated by PCR with oligonucleotide primers the sequence of which was derived from the N-terminal and internal amino acid sequences. Determination of the nucleotide sequence showed that the gene is located distally and as a hitherto uncharacterised gene within the hyc operon, coding for hydrogenase 3 components. It was designated hycI. The HycI protease has a molecular mass of 17 kDa and is a monomer. Its cleavage reaction is not inhibited by conventional inhibitors of serine and metalloproteases, which correlates with the fact that the sequence does not contain signature motifs characteristic of serine-, metallo-, cysteine- or acid proteases. Homologous genes are present in other transcriptional units coding for hydrogenases.

Amino Acid Sequence↗
PubMed1995

The gray-scale ink-jet printer: value in making hard copies of digital images.

Referring physicians often are supplied with copies of images to illustrate a report of the findings of a radiologic study or so that the radiologist can retain the original images. The increasing costs of production, film, and recovery of chemicals have enhanced the requirement for a clean, low-cost dry printing process. An ink-jet gray-scale paper printer (Unitone, Scitex Medical Systems, Bedford, MA) can print high-quality (300 dots per inch [dpi]) images with an effective 10-bit gray scale range by using the Hertz continuous ink-jet method [1-3], which does not require the use of a darkroom or hazardous chemicals. Several types of media (matte paper, glossy paper, transparency film) with a printing area of 26.9 x 43.7 cm (10.6 x 17.4 inches) may be used. The consumables are approximately 50-70% less expensive than the cost of silver halide film, providing a cost advantage over film for referral and archival copies. The results of an initial evaluation of the ink-jet printer at our institution are reported here.

Computer Peripherals↗
PubMed1993

The product of the hypB gene, which is required for nickel incorporation into hydrogenases, is a novel guanine nucleotide-binding protein.

The products of the hyp operon genes are essential for the formation of catalytically active hydrogenases in Escherichia coli. At least one of these auxiliary proteins, HYPB, appears to be involved in nickel liganding to the hydrogenase apoprotein, since mutations in hypB can be phenotypically suppressed by high nickel concentrations in the medium (R. Waugh and D. H. Boxer, Biochimie 68:157-166, 1986). To approach the identification of the specific function of HYPB, we overexpressed the hypB gene and purified and characterized the gene product. HYPB is a homodimer of 31.6-kDa subunits, and it binds guanine nucleotides, with a Kd for GDP of 1.2 microM. The protein displays a low level of GTPase activity, with a kcat of 0.17 min-1. The apparent Km for GTP, as measured in the GTP hydrolysis reaction, was determined to be 4 microM. A chromatography system was established to measure nickel insertion into hydrogenase 3 from E. coli and to determine the effects of lesions in hypB. Nickel appears to be associated only with the processed large subunit of hydrogenase 3 in the wild type, and hypB mutants accumulate the precursor form of this subunit, which is devoid of nickel. The results are discussed in terms of a model in which HYPB is involved in nickel donation to the hydrogenase apoprotein and in which GTP hydrolysis is thought to reverse the interaction between either HYPB or another nickel-binding protein and the hydrogenase apoprotein after the nickel has been released.

Amino Acid Sequence↗
PubMed1993

[The value of spiral-CT in primary and secondary liver neoplasms].

Sixty-one patients in whom primary or secondary malignomas of the liver were suspected on the basis of ultrasound examination were examined with spiral CT and sequential CT during i.v. administration of contrast medium. In four further cases spiral CT-angiography (spiral-CTA) was performed. Advantages and disadvantages of spiral volume CT are described.

Adult↗
PubMed1991

The foot and footwear.

In the field of sports medicine we see increasing numbers of foot- and leg-related injuries that could have been avoided, either totally or in part, had the individual chosen the proper footwear. There is no such thing as the ideal shoe for all types of feet and all terrains, however. When an athlete has a chronic problem that does not respond to properly fitted shoes, a physician consultation should be considered.

Athletic Injuries↗
PubMed1990

IL-3, IL-4, and IL-6 enhance IFN-gamma-dependent bone marrow natural suppressor activity.

The ability of murine bone marrow (BM) natural suppressor (NS) cells to suppress a Con A proliferation assay was greatly enhanced by supernatant obtained from the T cell hybridoma D9C1.12.17. Of the lymphokines produced by this hybridoma, three were found to enhance suppression: interleukin-3 (IL-3), IL-4, and IL-6. These molecules enhanced suppression of both unirradiated and irradiated (2000 R) BM cells indicating that augmented suppression was not just due to proliferation of NS cells. The ability of all three of the lymphokines to enhance BM suppression could be blocked by anti-interferon-gamma (IFN-gamma) antibody. These results indicate that (1) NS cell activity is not radiosensitive and (2) that two signals may be required for maximal NS cell suppression, one being a lymphokine-mediated signal and the other IFN-gamma.

Animals↗
PubMed1990

Estrogen and progesterone receptors in endometrial cancer and their prognostic relevance.

Three hundred and nine malignant endometrial tumors were biochemically analyzed with respect to estrogen (ER) and progesterone (PR) receptors. Fifty-seven percent of endometrial carcinomas were ER and PR positive (greater than or equal to 50 fmole/mg of cytosol protein); 24% were negative for both receptors. Five sarcomas and 16 of 21 mixed müllerian tumors were receptor negative. Receptor status correlated with clinical stage and grade of histological differentiation, but not with myometrial invasion. Anamnestic data on patients showed no differences between those with receptor-negative and receptor-positive tumors. Five-year survival rate (stage I) and median survival time (stages II-IV, recurrences) for patients with ER+/PR+ and ER-/PR+ endometrial cancer were significantly better than for ER-/PR- and ER+/PR- patients. A multivariate analysis demonstrated progesterone receptor as a significant prognostic factor next to clinical stage. Estrogen receptor had no significant prognostic relevance. A retrospective analysis of gestagen treatment and progesterone receptor status confirms the importance of PR, possibly independent of hormonal treatment.

Adenocarcinoma↗
PubMed1989

Murine natural suppressor cells in the newborn, in bone marrow, and after cyclophosphamide. Genetic variations and dependence on IFN-gamma.

Natural suppressor (NS) cells are potent, Ag nonspecific, MHC-unrestricted inhibitors of immune responses. Murine NS activity is found in several situations, including adult bone marrow (BM) and neonatal/newborn spleen, and spleen following total lymphoid irradiation, after BM transplantation and after cyclophosphamide (CY) treatment. Using three of these situations (adult BM, newborn spleen, and spleen after CY treatment), the strain distribution of NS cell activity was assessed. A wide variation in potency is seen in both naturally occurring (adult BM and newborn spleen) and induced (after CY treatment) NS cell activity. Up to 10-fold differences in NS activity are seen between high and low NS strains. This reflects an intrinsic genetic variation between mouse strains in both naturally occurring and CY-induced NS cell activity. Thus, a strain with high NS activity at birth, has high NS activity in its BM as an adult and in its spleen after CY treatment. Of the strains tested, B10.D2 has the highest NS cell activity while BALB/c has the lowest, and the F1 between these two strains is intermediate in NS activity. Finally, the NS cell activity from all strains tested required IFN-gamma for expression of its inhibitory activity.

Aging↗
PubMed1989

[Determination of the endotoxin content of egg products using a miniaturized chromogenic Limulus test].

A chromogenic Limulus amoebocyte lysate assay was applied to monitor endotoxin concentration in egg products. Analysis of differently contaminated whole egg probes revealed a strong correlation of endotoxin concentration to total bacterial count 6 x 10(4) cfu x ng-1, where cfu = colony-forming unit) as well as to number of Enterobacteriaceae (1 ng/7 x 10(2) cfu). Similar relations were also found for egg white and egg yolk probes. A significant influence of heat pretreatment of egg probes (65 degrees C, 60 min) on endotoxin detection could be excluded. Up to a concentration of 10 mg x ml-1 endotoxin-free whole egg material did not interfere with the test system. A miniaturized version of the chromogenic Limulus test, which can be carried out in microtiter plates, is described.

Animals↗
PubMed1988

Suppression of cytotoxic T-cell generation by natural suppressor cells from mice with GVHD is partially reversed by indomethacin.

Natural suppressor cells from the spleens of mice with graft-versus-host disease produced across minor histocompatibility barriers inhibit the in vitro generation of alloreactive cytotoxic T lymphocytes by spleen cells from normal mice. The mechanism of natural suppression was studied; suppression does not require direct cell contact with targets. Exogenous interleukin-2 has no effect in reversing suppression while indomethacin partially reverses the suppression mediated by natural suppressor cells.

Animals↗
PubMed1988

Evidence that IFN-gamma is responsible for natural suppressor activity in GVHD spleen and normal bone marrow.

Natural suppressor (NS) cells are capable of suppressing immunological responses in a nonspecific manner. Previously, we have described NS cells in the spleens of mice undergoing chronic graft-versus-host disease (GVHD) and also in normal B10.D2 bone marrow (BM). NS cells obtained from these environments appear dependent upon lymphokines for their ability to manifest suppression. In this report, with anti-IFN-gamma antibody, we show that IFN-gamma is necessary for NS cell activation. Anti-IFN-gamma antibody is able to remove the ability of NS cells to suppress a concanavalin A (Con A) proliferation assay. Also, anti-IFN-gamma antibody removes the ability of rIL-2, lectin-free Con A supernate (CAS), and recombinant IFN-gamma (rIFN-gamma) to enhance NS suppression of lipopolysaccharide response. By these criteria, IFN-gamma is required for NS cell activation, and rIL-2 may act indirectly by its ability to stimulate IFN-gamma synthesis. These results are discussed in the context of the immuno-suppression seen in human BM transplantation.

Animals↗