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Biomedical subjects

G Richter

Publications and source records attributed to G Richter.

At least 127 records · Page 7Linked to original sources
PubMed1994

Acetylsalicylic acid in the prevention of early stenosis and occlusion of transjugular intrahepatic portal-systemic stent shunts: a controlled study.

Stenosis or occlusion of the transjugular intrahepatic portal-systemic stent shunt may be initiated by aggregation and activation of thrombocytes on the surface of the metallic stent material. To find effective prevention of this event, we conducted a controlled trial administering acetylsalicylic acid for 3 mo. Forty-four patients (8 women and 36 men) with portal hypertension were included in this study. The patients were randomized into a group receiving 100 mg acetylsalicylic acid/day (n = 21) or into a control group (n = 23). Treatment was started immediately after transjugular intrahepatic portal-systemic stent shunt. Three months after transjugular intrahepatic portal-systemic stent shunt, 15 patients in the acetylsalicylic acid group and 19 patients in the control group underwent clinical reevaluation, gastroscopy and recatheterization with determination of the portal-systemic pressure gradient. No variceal bleeding occurred in any patients. In four patients in the acetylsalicylic acid group, erosive gastritis was observed in gastroscopy in contrast to only one patient in the control group. Complete patency of the stent was noted in 10 of 15 patients in the acetylsalicylic acid group and in 14 of 19 patients in the control group. Transjugular intrahepatic portal-systemic stent shunt restenosis associated with a significant increase of the portal-systemic gradient occurred in five patients in the acetylsalicylic acid group, which required redilation in all and additional stent placement for expansion of the stented tract in two patients. In the control group, redilation was necessary in five patients with additional stent extension in two patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Interleukin 10 transfected into Chinese hamster ovary cells prevents tumor growth and macrophage infiltration.

Expression of cytokines in tumor cells provides a sensitive modality to analyze the consequences of local cytokines in vivo on tumor infiltrating cells and tumorigenicity. We have transfected Chinese hamster ovary (CHO) cells with an interleukin 10 (IL-10) expression vector. CHO-IL10 cells although unaltered with respect to their in vitro growth lost tumorigenicity, both in nude and in SCID mice and in an IL-10 dose dependent manner. In addition, CHO-IL10 cells suppressed the growth of equal numbers of coinjected but not of contralaterally injected CHO cells. Immunohistology with anti-CR3/Mac-1 and anti-Mac-3 monoclonal antibodies revealed that CHO tumors were substantially infiltrated by macrophages. However, in CHO-IL10 tumors macrophages were virtually absent within the tumor tissue. Our results suggest that IL-10 indirectly suppresses tumor growth of certain tumors by inhibiting infiltration of macrophages which may provide tumor growth promoting activity.

Animals↗
PubMed1993

Eosinophils infiltrating interleukin-5 gene-transfected tumors do not suppress tumor growth.

Tumor-associated eosinophils have been observed in human tumors and in experimental tumor models, but their function is poorly understood. To study the role of eosinophils during tumor growth, the plasmacytoma J558L and the mammary adenocarcinoma TS/A were transfected with an expression vector encoding the murine gene for interleukin-5 (IL-5), a cytokine inducing proliferation and activation of eosinophils. Injection of parental cells, mock-transfectants and IL-5-producing cells into syngeneic mice showed that local IL-5 secretion induced rapid tumor infiltration by eosinophils, as evidenced by immunohistochemical staining, but nevertheless did not alter the tumor growth kinetics of IL-5 transfectants. Therefore, the mere presence of IL-5 and eosinophils was not sufficient to induce a protective host immune response.

Animals↗
PubMed1993

Characterization of insulin-like growth factor II receptors in human small cell lung cancer cell lines.

Small cell lung cancer (SCLC) cell lines were investigated for the expression of insulin-like growth factor (IGF) II receptor by means of radioreceptor assays, cross-linking techniques, and Northern blot analysis. 125I-IGF II binds to both the IGF I and the IGF II receptor on intact SCLC cells. Detailed receptor assays performed on microsomal and plasma membranes gave evidence that 125I-IGF II binds with high affinity (70-80 pM) to the IGF I receptor and with low affinity (2-4 nM) to the IGF II receptor, and not conversely. The presence of mannose-6-phosphate enhanced the binding of 125I-IGF II to the IGF II receptor of SCLC. Mannose-6-phosphate also increased the efficiency of N-hydroxysuccinimide ester in cross-linking 125I-IGF II to the IGF II receptor and facilitated the cross-linking of 125I-IGF II to a second protein of 240-250 kDa. Soluble IGF II receptor was also detected in conditioned media of SCLC cell lines.

Blotting, Northern↗
PubMed1993

A novel blue light- and abscisic acid-inducible gene of Arabidopsis thaliana encoding an intrinsic membrane protein.

Continuous irradiation with blue light (400-500 nm) induces flower formation in plantlets of Arabidopsis thaliana (C24) while red light (600-700 nm) is ineffective. This observation started a search for genes that are activated by blue light and initiate the morphogenic programme leading to flower formation. Several genes were identified via their cDNAs. From these clone AthH2, with an open reading frame for a hydrophobic 30.5 kDa polypeptide, was selected for further characterization of the corresponding gene. From a genomic library a DNA fragment of about 6.4 kb was isolated, comprising the coding region as well as 5'-upstream and 3'-downstream flanking segments. The coding region is composed of four exons, which specify a polypeptide of 286 amino acids. Several potential regulatory elements were found between position -670 and -1140 including GA and ABA sequence motifs. The latter could account for the observed induction of the AthH2 gene by ABA. Southern blot analysis of Arabidopsis genomic DNA suggests that the AthH2 gene is encoded by a single-copy gene. Hydropathy plots and secondary structure analysis of the putative polypeptide predict six membrane-spanning domains implicating a function as transmembrane channel protein. It displays significant homology with the proteins TR7a of pea (82%) and RD 28 of A. thaliana (68%).

Abscisic Acid↗
PubMed1993

[The use of native triticale in poultry. 3. Use in laying hens].

In three trials with a total of 3240 white laying hybrids, 10 to 72% Triticale of the variety "Grado" was used as a substitute for maize and wheat. The feeding of Triticale had no influence on feed consumption, laying performance, feed efficiency, mortality or weight gain. In two of three trials the egg weight was lowered with an increasing amount of Triticale in the diet. After supplementation of 1 or 1.5% sunflower oil to the diets with 50 resp. 72% Triticale the egg weight increased again to the level of the control group. With the exception of one group, there was no correlation between breaking strength and deformation of the eggs. The colour intensity of the egg yolk was decreased with increasing amounts of Triticale in the diet. It can be concluded, that laying hen feed supplemented with oil may contain up to 50% Triticale, but in non-supplemented diets the highest amount of Triticale should be only 20% because of the risk of linoleic acid shortage.

Animal Feed↗
PubMed1993

[Use of microbial phytase at different phosphorus supply levels in broiler fattening. 1. Effect on fattening performance and tibia stability].

Two trials with 720 male and female Lohmann-broilers each and a fattening period of 35 days were carried out to study the effects of different phytase supplementations (0; 300; 700 units per kg feed). The basal diets with only ingredients of plant origin or of plant and animal origin contained between 0.4 and 0.5 per cent total-P. The supplementation of inorganic P was 0; 338; 675 and 1350 mg per kg feed. The feed intake increased on average by 15 and 17% resp. after adding of 300 or. 700 units phytase to diets with different phosphorus supply. The body weight of broilers increased also in dependence of feed intake. The feed conversion was not influenced by the different phytase and inorganic P-supply. The bone stability examined as bending and breaking strength of tibia was improved by supplementation of phytase and inorganic P. Based on the fattening parameters 300 units phytase can replace 0.06 per cent inorganic P in the diet.

6-Phytase↗
PubMed1993

Biosynthesis of riboflavin: cloning, sequencing, mapping, and expression of the gene coding for GTP cyclohydrolase II in Escherichia coli.

GTP cyclohydrolase II catalyzes the first committed step in the biosynthesis of riboflavin. The gene coding for this enzyme in Escherichia coli has been cloned by marker rescue. Sequencing indicated an open reading frame of 588 bp coding for a 21.8-kDa peptide of 196 amino acids. The gene was mapped to a position at 28.2 min on the E. coli chromosome and is identical with ribA. GTP cyclohydrolase II was overexpressed in a recombinant strain carrying a plasmid with the cloned gene. The enzyme was purified to homogeneity from the recombinant strain. The N-terminal sequence determined by Edman degradation was identical to the predicted sequence. The sequence is homologous to the 3' part of the central open reading frame in the riboflavin operon of Bacillus subtilis.

Amino Acid Sequence↗
PubMed1993

Solubilization of active receptors for glucagon-like peptide-1(7-36)amide from rat lung membranes.

We report on a protocol that allows the solubilization of active glucagon-like peptide (GLP)-1-(7-36)amide receptors from rat lung membranes. Digitonin-solubilized GLP-1(7-36)amide binding proteins from lung membranes most effectively, whereas (3-[(3-cholamidopropyl)- dimethylamino]-1-propane-sulfonate was less affective, and octyl-beta-glucoside, Triton X-100 and Lubrol PX were almost ineffective. Solubilization of binding activity was optimal at a digitonin concentration of 1%, a protein-to-detergent ratio of 1:10, and a pH between 7.0 and 8.0. Binding of GLP-1(7-36)amide to solubilized receptors was dependent on the concentration of solubilized protein. The presence of certain mono- and divalent cations was crucial for binding of GLP-1(7-36)amide to solubilized receptors. Scatchard analysis of the binding data revealed a single class of binding sites with dissociation and maximum binding constant values of 0.40 +/- 0.20 nM and 80.0 +/- 26.0 fmol/mg protein for membrane bound and 7.0 +/- 0.6 microM and 12.0 +/- 6.0 nmol/mg protein for solubilized receptors, respectively. In cross-linking experiments 125I-labeled GLP-1(7-36)amide was covalently attached to GLP-1(7-36)amide receptors on lung membranes. The apparent molecular mass of the solubilized receptor was 55,000 Da. This was proven in another experiment when receptor was consecutively cross-linked after solubilization. Nonhydrolyzable GTP analogues (GTP gamma S or GDP beta S) were unable to reduce GLP-1(7-36)amide-binding at solubilized receptors. This argues that the receptor is solubilized as a single protein and not as a receptor-G protein complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

GLP-1 stimulates secretion of macromolecules from airways and relaxes pulmonary artery.

Recent data revealed the existence of specific receptors for glucagon-like peptide-1(7-36)amide (GLP-1) on rat lung membranes. Utilizing slide-mount autoradiography of fresh frozen lung tissue sections, we have localized binding sites for GLP-1 on mucous glands in the trachea and on vascular smooth muscle of the pulmonary artery. When tracheas were incubated in a modified Ussing chamber, the addition of GLP-1 to the submucosal side increased 35S-sulfate-labeled macromolecule secretion (191 +/- 12% above basal, P < 0.005). The optimal secretory response elicited by GLP-1 was approximately 23% of the maximal secretory response after a maximal acetylcholine stimulation. Other proglucagon-derived peptides such as glucagon, oxyntomodulin, and GLP-2 had no effect. In isolated rings of arteries, GLP-1 (10(-8) to 10(-5) M) induced a dose-dependent and time-reversible relaxation of preconstricted arteries. In a preparation with denuded epithelium, GLP-1 lost its effect. In conclusion, GLP-1 might represent another neuropeptide that acts as neurotransmitter of the peptidergic, nonadrenergic-noncholinergic nervous system that innervates the airways.

Animals↗
PubMed1992

Analysis of cytokine mRNA levels in interleukin-4-transgenic mice by quantitative polymerase chain reaction.

Interleukin (IL)-4-transgenic mice were used as a model system to study the consequences of low levels of IL-4 expression for the expression of other cytokines examined by quantitative polymerase chain reaction (PCR). For this purpose, a plasmid was constructed which contains, in tandem array, 5' and 3' primer sequences specific for the cytokine genes IL-1 to IL-6, tumor necrosis factor (TNF), lymphotoxin (LT), interferon (IFN)-gamma and beta-actin. During co-amplification, target and control DNA compete for the primers and the amount of PCR product is proportional to the amount of input DNA. Competitive PCR was performed first to adjust the cDNA to be compared to identical concentrations of beta-actin cDNA and subsequently to determine cytokine mRNA levels from spleen cells of normal and IL-4-transgenic animals. The sensitivity of this approach was demonstrated by the capability to detect a twofold difference in IL-4 mRNA levels between IL-4-transgenic heterozygous and homozygous animals. Upon lipopolysaccharide activation, the IL-4 transgene which is expressed essentially in B lymphocytes was induced approximately 50-fold. Several cytokine mRNA such as those coding for IL-5, IL-6, IFN-gamma and also the IL-4 receptor were found to be up-regulated in IL-4-transgenic mice, whereas IL-1, IL-2, IL-3, TNF and LT mRNA levels did not seemed to be influenced by IL-4. A possible functional significance of the elevated IFN-gamma mRNA was demonstrated by showing that (a) CD23 expression was not increased, and (b) Mac-1+ cells were markedly increased in the spleen of transgenic mice.

Animals↗
PubMed1992

Interleukin-4-mediated tumor suppression in nude mice involves interferon-gamma.

The molecular events during the anti-tumor response induced by interleukin (IL)-4 were investigated by quantitative polymerase chain reaction. The growth of Chinese hamster ovary cells transfected to produce IL-4 (CHO.T1) was strongly suppressed when cells were injected intraperitoneally into nude mice and this suppression was accompanied by the rapid accumulation of activated macrophages. Peritoneal cells from such mice were analyzed for mRNA induced by IL-4. Correlating with a high local IL-4 concentration, several transcripts were found to be up-regulated during the early phase of the anti-tumor response [IL-4 receptor, IL-5, tumor necrosis factor (TNF) and interferon (IFN)-gamma]. The functional relevance of the elevated mRNA levels was analyzed by injection of CHO.T1 cells together with anti-cytokine monoclonal antibodies (mAb). In contrast to anti-IL-5 and anti-TNF mAb, an anti-IFN-gamma mAb interfered with the anti-tumor response demonstrating the involvement of IFN-gamma during the IL-4-induced tumor suppression. Tumor growth in anti-IFN-gamma mAb-treated animals was significantly delayed in comparison to anti-IL-4 mAb-treated mice, suggesting that IFN-gamma-independent effector cells may also be involved.

Animals↗
PubMed1992

[Effect of the manganese content in laying hen feed with different Ca and mineral levels on the egg shell quality and bone mineralization of hens].

Four experiments with 270, 44, 432 and 66800 Leghorn hens were carried out to investigate the influence of various Mn additions to diets differed in mineral or Ca contents on egg shell quality. The addition of 300 mg Mn/kg diet improved significantly egg shell breaking strength by 4 N over one year. The supply of 50-500 mg Mn/kg diet for 10-24 weeks of the second half of laying year did not influence the egg shell quality. Addition of mineral mixture or Ca grit to layer rations with adequate or higher Mn levels did not influence egg shell strength. High mineral content in a low manganese diet increased number of cracks by 3%. Strength, weight and ash content of tibia were significantly reduced by feeding a low mineral level. Addition of 50-150 mg Mn per kg low mineral diet normalized partially tibia stability in young hens. It was concluded that supplied dietary Manganese influences calcification positively only in young hens. High levels of Ca did not influence the effects of Mn. 50 mg Mn per kg layers mixture have been considered as an essential supply.

Animal Feed↗
PubMed1992

Biosynthesis of riboflavin: cloning, sequencing, and expression of the gene coding for 3,4-dihydroxy-2-butanone 4-phosphate synthase of Escherichia coli.

3,4-Dihydroxy-2-butanone 4-phosphate is biosynthesized from ribulose 5-phosphate and serves as the biosynthetic precursor for the xylene ring of riboflavin. The gene coding for 3,4-dihydroxy-2-butanone 4-phosphate synthase of Escherichia coli has been cloned and sequenced. The gene codes for a protein of 217 amino acid residues with a calculated molecular mass of 23,349.6 Da. The enzyme was purified to near homogeneity from a recombinant E. coli strain and had a specific activity of 1,700 nmol mg-1 h-1. The N-terminal amino acid sequence and the amino acid composition of the protein were in agreement with the deduced sequence. The molecular mass as determined by ion spray mass spectrometry was 23,351 +/- 2 Da, which is in agreement with the predicted mass. The previously reported loci htrP, "luxH-like," and ribB at 66 min of the E. coli chromosome are all identical to the gene coding for 3,4-dihydroxy-2-butanone 4-phosphate synthase, but their role had not been hitherto determined. Sequence homology indicates that gene luxH of Vibrio harveyi and the central open reading frame of the Bacillus subtilis riboflavin operon code for 3,4-dihydroxy-2-butanone 4-phosphate synthase.

Amino Acid Sequence↗
PubMed1992

Increased prevalence of IgG-induced sensitization and hypersensitivity pneumonitis (humidifier lung) in nonsmokers exposed to aerosols of a contaminated air conditioner.

Specific IgG antibodies against antigens of a contaminated air conditioner were estimated in serum of 134 workers of a printing company. Altogether 64% of the workers investigated revealed significantly elevated levels (> 3 U/ml) of IgG antibodies specific to these antigens as compared to a nonexposed control group. The occurrence of IgG antibodies for microbial extracts were 25% for Fusarium, 23% for Penicillium notatum, 13% for Alternaria tenuis, 12% for Aureobasidium pullulans, 9% for Sphaeropsidales species, 3% for Micropolyspora faeni, 2% for Aspergillus fumigatus and 2% for Thermoactionomyces vulgaris. Out of the 86 workers with elevated IgG antibodies for air conditioner antigens, 59 were nonsmokers. Considering a cut-off level of 10 U/ml IgG for high values, the proportion of smokers to nonsmokers becomes even more pronounced (6 to 36 respectively, binominal test p < 0.001). This is despite the fact that the distribution of smokers and nonsmokers among the 134 workers is approximately equal (60 to 74). All 3 workers with clinical diagnosis of humidifier lung or humidifier fever belonged to the nonsmoker group. Our findings indicate that crude water extracts of contaminated air conditioners are the best choice as antigen source for the diagnosis of humidifier lung in exposed workers. Nonsmokers are shown to have a high risk for immunological sensitization.

Aerosols↗