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G Zimmermann

Publications and source records attributed to G Zimmermann.

At least 37 records · Page 2Linked to original sources
PubMed2001

Pyrimidine-2,4,6-Triones: a new effective and selective class of matrix metalloproteinase inhibitors.

Matrix metalloproteinases (MMPs) are a family of zinc endopeptidases that have been implicated in various disease processes. Different classes of MMP inhibitors, including hydroxamic acids, phosphinic acids and thiols, have been previously described. Most of these mimic peptides and most likely bind in a similar way to the corresponding peptide substrates. Here we describe pyrimidine-triones as a completely new class of metalloprotease inhibitors. While the pyrimidine-trione template is used as the zinc-chelating moiety, the substituents have been optimized to yield inhibitors comparable in their inhibition efficiency of matrix metalloproteinases to hydroxamic acid derivatives such as batimastat. However, they are much more specific for a small subgroup of MMPs, namely the gelatinases (MMP-2 and MMP-9).

Chelating Agents↗
PubMed2000

Detection of membrane-bound tumor necrosis factor (TNF): an analysis of TNF-specific reagents.

Tumor necrosis factor (TNF) exists in two bioactive forms, the membrane integrated form and the proteolytically derived soluble cytokine. Both forms of TNF are involved in a variety of different physiological and pathophysiological situations. Here we analyzed different human and mouse TNF-specific reagents for their ability to determine the expression of membrane-expressed TNF. The data prove some antibodies to be very useful for the analysis of transmembrane TNF expression because these antibodies distinguish between the transmembrane form of TNF and soluble TNF bound to cellular TNF receptors. In addition, we found that recombinant human TNF receptor fusion proteins are advantageous tools to analyze both human and mouse transmembrane TNF expression.

Animals↗
PubMed2000

Evaluation of insecticide ear tags containing ethion for control of pyrethroid resistant Haematobia irritans (L.) on dairy cattle.

A field study was conducted in central Argentina to evaluate the efficacy of ear tags containing 36% ethion against pyrethroid resistant populations of Haematobia irritans on grazing dairy cattle. The treated group consisted of 45 milking Holstein cows which received two tags per head and the control consisted of 22 dry cows from the same cohort. Treated and control groups were grazed on similar lucerne pastures separated for a minimum distance of 800 m but they were not isolated from other cattle herds on the same or contiguous properties. In both groups, horn fly estimation were made weekly by examining cattle in the pastures with the aid of binoculars. The percentage reduction of fly numbers on treated cows was considered as efficacy of control provided by the tags. The ethion ear tags provided a range of 85-99% reduction in horn fly numbers for 16 weeks. During this period, the weekly mean number of H. irritans on the tagged cows ranged between 0.44 and 28.26 compared with 143.5 and 239.1 in control animals. The ethion ear tags could be a useful tool for the control of H. irritans mainly in areas where populations of this insect have developed resistance to pyrethroid insecticides.

Animal Identification Systems↗
PubMed2000

Biocompatible alginate from freshly collected Laminaria pallida for implantation.

A simple procedure is described for the extraction and purification of alginate from the inner stipes of the kelp Laminaria pallida. Alginate yield was about 10-15% of the dry mass, with a 70:30 mannuronic/guluronic acid ratio. Analysis of the purified alginate revealed a low polyphenol content while proteins were below detection level. The purified alginate was highly viscous, with 10-15 mPa s and 281 mPa s for a 0.1% and 0.5% solution, respectively, indicating a very high molecular mass (larger than 250 kDa). Bead formation occurred in the presence of divalent cations, but also in the presence of artificial serum (FCSIII) without added divalent cations. The biocompatibility of the alginate was tested with the in vitro mice lymphocyte test as well as by implantation of Ba2+ cross-linked beads beneath the kidney capsule of BB/OK rats. There was no evidence for significant mitogenic activity or fibrotic reaction. Biocompatibility of the alginate was also demonstrated by the encapsulation of human chondrocytes into Ca2+ cross-linked alginate beads. Immobilized chondrocytes grew and remained functional (i.e. they produced collagen).

Alginates↗
PubMed1999

Induction of cell death by tumour necrosis factor (TNF) receptor 2, CD40 and CD30: a role for TNF-R1 activation by endogenous membrane-anchored TNF.

Several members of the tumour necrosis factor receptor (TNF-R) superfamily can induce cell death. For TNF-R1, Fas/APO-1, DR3, DR6, TRAIL-R1 and TRAIL-R2, a conserved 'death domain' in the intracellular region couples these receptors to activation of caspases. However, it is not yet known how TNF receptor family members lacking a death domain, such as TNF-R2, CD40, LT-betaR, CD27 or CD30, execute their death-inducing capability. Here we demonstrate in different cellular systems that cytotoxic effects induced by TNF-R2, CD40 and CD30 are mediated by endogenous production of TNF and autotropic or paratropic activation of TNF-R1. In addition, stimulation of TNF-R2 and CD40 synergistically enhances TNF-R1-induced cytotoxicity. These findings describe a novel pro-apoptotic mechanism induced by some members of the TNF-R family.

Animals↗
PubMed1999

Activating mutation of adenylyl cyclase reverses its inhibition by G proteins.

We have implemented a yeast genetic selection developed previously by our laboratory to identify mutant mammalian type V adenylyl cyclases insensitive to inhibition by G(ialpha.) One mutation isolated was localized to the first cytoplasmic domain at a Phe residue (position 400), which is conserved in all nine isoforms of membrane-bound mammalian adenylyl cyclase. Biochemical characterization of the F400Y mutant revealed a dramatic conversion of the G(ialpha) response from inhibitory to stimulatory. This mutation results in additional activating effects. The mutant exhibits an enhanced sensitivity toward activation by either G(salpha) or forskolin. Synergism between G(salpha) and forskolin is not observed for the F400Y mutant, presumably because the mutant already is in the sensitized state. Additionally, an enhancement of the basal unstimulated activity was observed. This mutation, which is the first demonstration of an activating point in a mammalian adenylyl cyclase, mimics a sensitized conformation of the wild-type enzyme that underlies the synergism between stimulatory inputs, and additionally, removes the inhibitory regulatory input provided by G(ialpha). Because sensitizing adenylyl cyclase toward its stimulators can have profound biological implications, this raises the possibility that naturally occurring mutations resembling those at the Phe400 residue may be associated with human disease states.

Adenylyl Cyclase Inhibitors↗
PubMed1999

Metabolism of retigabine (D-23129), a novel anticonvulsant.

Retigabine (D-23129, N-(2-amino-4-(4-fluorobenzylamino)-phenyl) carbamic acid ethyl ester) is a potent anticonvulsant in a variety of animal models. Rats metabolized [14C]retigabine mainly through glucuronidation and acetylation reactions. Glucuronides were detected in incubates with liver microsomes or slices, in plasma, and in bile and feces but were absent in urine (0-24 h) that contained about 2% of the dose as retigabine and approximately 29% of the dose in > 20 metabolites, which are derived mainly from acetylation reactions. About 67% of the radioactivity was excreted into feces, approximately 10% of the dose as glucuronide. The metabolite pattern in the urine (0-24 h) of dogs was comparatively simple in that retigabine (13%), retigabine-N-glucuronide (5%), and retigabine-N-glucoside (1%) were present. In the same 24-h interval, about 39% of unchanged retigabine was excreted into feces. Plasma profiling and spectroscopic analysis (liquid chromatography with tandem mass spectrometry NMR) of two isolated urinary metabolites obtained after single oral dosing of 600 mg retigabine in healthy volunteers indicated that both acetylation and glucuronidation are major metabolic pathways of retigabine in humans. We found that in vitro assays with liver slices from rat and humans reveal the major circulating metabolites in vivo.

Animals↗
PubMed1998

Mutations uncover a role for two magnesium ions in the catalytic mechanism of adenylyl cyclase.

The recent determination of the crystal structure of adenylyl cyclase has elucidated many structural features that determine the regulatory properties of the enzyme. In addition, the characterization of adenylyl cyclase by mutagenic techniques and the identification of the binding site for P-site inhibitors have led to modeling studies that describe the ATP-binding site. Despite these advances, the catalytic mechanism of adenylyl cyclase remains uncertain, especially with respect to the role that magnesium ions may play in this process. We have identified four mutant mammalian adenylyl cyclases defective in their metal dependence, allowing us to further characterize the function of metal ions in the catalytic mechanism of this enzyme. The wild-type adenylyl cyclase shows a biphasic Mg2+ dose-response curve in which the high-affinity component displays cooperativity (Hill coefficient of 1.4). Two mutations (C441R and Y442H) reduce the affinity of the adenylyl cyclase for Mg2+ dramatically without affecting the binding of MgATP, suggesting that there is a metal requirement in addition to the ATP-bound Mg2+. The results of this study thus demonstrate multiple metal requirements of adenylyl cyclase and support the existence of a Mg2+ ion essential for catalysis and distinct from the ATP-bound ion. We propose that adenylyl cyclase employs a catalytic mechanism analogous to that of DNA polymerase, in which two key magnesium ions facilitate the nucleophilic attack of the 3'-hydroxyl group and the subsequent elimination of pyrophosphate.

Adenosine Triphosphate↗
PubMed1998

Genetic selection of mammalian adenylyl cyclases insensitive to stimulation by Gsalpha.

We describe the development of a genetic system allowing for the isolation of mutant mammalian adenylyl cyclases defective in their responses to G protein subunits, thus allowing for the identification of structural elements within the cyclase that are responsible for the recognition of these regulators. Expression of mammalian type V adenylyl cyclase in a cyclase-deleted yeast strain can conditionally complement the lethal phenotype of this strain. Type V adenylyl cyclase-expressing yeast grow only when the cyclase is activated by coexpression of Gsalpha or addition of forskolin to the medium; however, growth arrest is observed in the presence of both activators or under basal conditions. Utilizing this genetic system, we have isolated 25 adenylyl cyclase mutants defective in their response to Gsalpha. Sequence analysis and biochemical characterization of these mutants have identified residues in both cytoplasmic domains of the cyclase that are involved in the specific binding of and regulation by Gsalpha.

Adenylyl Cyclases↗
PubMed1998

The type 1 receptor (CD120a) is the high-affinity receptor for soluble tumor necrosis factor.

Tumor necrosis factor (TNF) can induce a variety of cellular responses at low picomolar concentrations. This is in apparent conflict with the published dissociation constants for TNF binding to TNF receptors in the order of 100-500 pM. To elucidate the mechanisms underlying the outstanding cellular sensitivity to TNF, we determined the binding characteristics of TNF to both human TNF receptors at 37 degrees C. Calculation of the dissociation constant (Kd) from the association and dissociation rate constants determined at 37 degrees C revealed a remarkable high affinity for TNF binding to the 60-kDa TNF type 1 receptor (TNF-R1; Kd = 1.9 x 10(-11) M) and a significantly lower affinity for the 80-kDa TNF type 2 receptor (TNF-R2; Kd = 4.2 x 10(-10) M). The high affinity determined for TNF-R1 is mainly caused by the marked stability of ligand-receptor complexes in contrast to the transient interaction of soluble TNF with TNF-R2. These data can readily explain the predominant role of TNF-R1 in induction of cellular responses by soluble TNF and suggest the stability of the TNF-TNF receptor complexes as a rationale for their differential signaling capability. In accordance with this reasoning, the lower signaling capability of homotrimeric lymphotoxin, compared with TNF, correlates with a lower stability of the lymphotoxin-TNF-R1 complex at 37 degrees C.

Antigens, CD↗
PubMed1998

HCG secretion by peripheral mononuclear cells during pregnancy.

Peripheral mononuclear cells (MNC) in culture release a biologically active hCG. This effect is detectable during pregnancy with a maximum between the 9th and 16th wk. Peripheral MNC already secrete hCG between the 7th and 11th d after embryo transfer. The secretion of hCG is activated by the PKC-activator TPA. TPA induces hCG release into the medium, thus causing a decrease in intracellular hCG content. In contrast, db-cAMP inhibites hCG secretion into the medium. Protein synthesis inhibitors of transcription and translation suppress the production and secretion of hCG. Peripheral natural killer (NK) cells (CD56+/CD16+) and monocytes (CD14+) show the highest secretion rates. IL-1 beta, IL-4, IL-6, IL-10, TNF alpha, and GM-CSF stimulate, whereas IL-2 and INF gamma inhibit, the hCG secretion of mononuclear cells. Flow cytometric experiments with hCG antibody demonstrate a binding of hCG on the surface of monocytes more than lymphocytes. The binding capacity is improved during pregnancy. Different hCG bands are shown in the Western blot analysis. We could confirm the mRNA of beta hCG and alpha CG are in MNC as well in the placental control. Peripheral MNC, first and foremost NK cells and monocytes, produce and secrete hCG during pregnancy, which play an important role for the corpus luteum rescue during the early gestational age and possibly for the immunotolerance.

Animals↗
PubMed1998

The presence of chorionic gonadotrophin beta subunit in normal cyclic human endometrium.

The aim of the present study was to determine whether human endometrial cells are able to secrete beta-chorionic gonadotrophin (betaCG). Immunohistochemical studies and in-situ hybridization were performed in order to provide evidence for the occurrence of betaCG in the normal endometrium in 15 patients in the proliferative phase, two patients in the periovulatory phase and 13 patients in the secretory phase. Neither immunohistochemical nor hybridization reactions could be recognized during the proliferative phase. In contrast, both protein and betaCG mRNA were observed in the glandular cells of the endometrium during the secretory phase. The results were supported by Western blotting of secretory phase endometrium extracts and the assessment of the functional secretory capacity of primary endometrium cultures. In comparison with cultured and separated cell fractions, tissue extracts showed a higher betaCG, indicating a regulatory interaction. In conclusion, betaCG can be demonstrated in normal human cyclic endometrium, suggesting a paracrine role in endometrial physiology.

Cells, Cultured↗
PubMed1997

[Fate of the calcium-dense proximal fragment in scaphoid fracture].

A cohort study with retrolective and prolective collection of data was carried out 49 of 99 patients with scaphoid fractures, initially treated by plaster cast immobilization and having developed a proximal fragment with increased bone density were studied. More than half of these patients had a good or excellent result according to the modified score of Green and O'Brien 29 of 49 proximal fragments with increased bone density returned to normal density: 45 of 49 showed bony union, and 35 of 49 showed no signs of posttraumatic arthrosis. The appearance of stripes with increased bone density in plain X-rays indicated a problem in the process of fracture healing; the clinical interpretation, however, was difficult. Four patients were treated by percutaneous canulated screw (Streli). These fractures showed bony union, the fragment with increased bone density returned to normal in three of four patients. All of these patients had some remaining clinical problems.

Adolescent↗
PubMed1997

[Risk assessment in ovarian hyperstimulation syndrome (OHS) using the machine learning system (Decision Master) in 155 in-vitro fertilisations and embryo-transfer (IVF/ET) cycles with a long stimulation protocol].

In 155 selected IVF/ET cycles stimulated with the long protocol 25 cycles with severe OHS are included which turned up later on (purposely overrepresented). An inductive machine learning program is described both in informatics and medical essentials. It is tested whether there exists an algorithm for ruling out the above-mentioned complication in the follicular phase of the same cycle already. By cross validation 89% of the OHS could be predicted and proven by practical rules using hormone and ultrasound values to avoid similar events in ongoing or further cycles.

Adult↗