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A Reimann

Publications and source records attributed to A Reimann.

33 records · Page 2Linked to original sources
PubMed1991

Affinity enhancement and transmembrane signaling are associated with distinct epitopes on the CD8 alpha beta heterodimer.

CD8 is a heterodimeric membrane glycoprotein on MHC class I-restricted T lymphocytes that cooperates with the alpha beta CD3 TCR in the recognition of MHC class I molecules presenting antigenic peptides. Co-operation has two components: enhancement of the affinity of MHC/peptide-TCR interaction, and signal transduction through the T cell membrane. The cytolytic function of CTL is primarily dependent on the affinity-enhancement component of CD8-TCR cooperation whereas activation of resting CD8+ T cells is primarily dependent on transmembrane signaling. Using a panel of mAb, two to the alpha-chain and three to the beta-chain of CD8, we investigated the relationships between epitopes and functional regions of the CD8 molecule. Two of the antibodies, one to the alpha-chain and one to the beta-chain of CD8, inhibit the cytolytic function of CTL but not the generation of CTL from resting T cells. Another two antibodies, also one to the alpha- and one to the beta-chain, inhibited the generation of CTL while enhancing the cytolytic function of CTL. These results suggest that both the alpha- and beta-chain of CD8 possess two distinct regions, one involved in affinity enhancement and the other in transmembrane signaling. The former may be the MHC class I-binding region whereas the latter may associate with the alpha beta CD3 TCR. The data can explain the apparent functional equivalence of CD8 alpha alpha homodimers and alpha beta heterodimers.

Animals↗
PubMed1991

Evolutionary aspects of cytochrome c oxidase.

The presence of additional subunits in cytochrome oxidase distinguish the multicellular eukaryotic enzyme from that of a simple unicellular bacterial enzyme. The number of these additional subunits increases with increasing evolutionary stage of the organism. Subunits I-III of the eukaryotic enzyme are related to the three bacterial subunits, and they are encoded on mitochondrial DNA. The additional subunits are nuclear encoded. Experimental evidences are presented here to indicate that the lower enzymatic activity of the mammalian enzyme is due to the presence of nuclear-coded subunits. Dissociation of some of the nuclear-coded subunits (e.g. VIa) by laurylmaltoside and anions increased the activity of the rat liver enzyme to a value similar to that of the bacterial enzyme. Further, it is shown that the intraliposomal nucleotides influence the kinetics of ferrocytochrome c oxidation by the reconstituted enzyme from bovine heart but not from P. denitrificans. The regulatory function attributed to the nuclear-coded subunits of mammalian cytochrome c oxidase is also demonstrated by the tissue-specific response of the reconstituted enzyme from bovine heart but not from bovine liver to intraliposomal ADP. These enzymes from bovine heart and liver differ in the amino acid sequences of subunits VIa, VIIa, and VIII. The results presented here are taken to indicate a regulation of cytochrome c oxidase activity by nuclear-coded subunits which act like receptors for allosteric effectors and influence the catalytic activity of the core enzyme via conformational changes.

Animals↗
PubMed1991

A comparative assessment of the roles of CD8 and CD2 in the functions of activated murine CD8+ T lymphocytes.

Both CD8 and CD2 are T cell surface receptors involved in physical cell interaction and in transmembrane signalling. The present paper addresses their role in the induction of two different functions of the cloned murine cytotoxic T cell C196: target cell lysis and IFN-gamma production. These functions were induced in C196 either by stimulation with the specific stimulator/target cell P815 or, bypassing specific recognition, by the aCD3 hybridoma 145-2C11 or by solid phase aTCR antibodies. These responses were tested for their susceptibility to inhibition/enhancement by a panel of aCD8 and aCD2 mAb. In addition, CD8 deficient and CD8/CD2 double-deficient variants of C196 were transfected with the CD8 and CD2 genes and the resulting cell lines were analysed for their functional capacities. The following results were obtained: (i) CD8 is primarily important in the specific recognition process of activated CTL; (ii) transmembrane signalling of activated CTL through the TCR does not require CD8, nor is it sensitive to modification through CD8; (iii) CTL can nevertheless be directly activated through CD8; however, this is restricted to induction of cytotoxicity but does not result in IFN-gamma production; (iv) CD2 does not seem to be important in any of these responses.

Animals↗
PubMed1991

Respiratory chain proteins.

Mammalian mitochondrial DNA codes for 13 proteins, which are all components of energy transducing enzyme complexes of the respiratory chain, i.e. the complexes which translocate protons across the inner mitochondrial membrane. The number of subunits of these enzyme complexes increase with increasing evolutionary stage of the organism. The additional nuclear coded subunits of the enzyme complexes from higher organisms are involved in the regulation of respiration, as demonstrated by the influence of intraliposomal ATP and ADP on the reconstituted cytochrome c oxidase (COX) from bovine heart. This regulation is not found with the reconstituted enzyme from P. denitrificans, which lacks the nuclear coded subunits. Some of the nuclear coded subunits occur in tissue-specific isoforms, as reported for COX and NADH dehydrogenase. Tissue-specific regulation of COX activity is also demonstrated by the differential effects of intraliposomal ADP on the kinetics of reconstituted COX from bovine liver and heart, which differ in subunits VIa, VIIa and VIII. At least 3 different COX isozymes occur in bovine liver, heart or skeletal muscle and smooth muscle. An evolutionary relationship between COX subunits VIa and VIc and between VIIa and VIIb is suggested based on the crossreactivity of monoclonal antibodies, amino acid sequence homology and hybridization at low stringency of PCR-amplified cDNAs for subunits VIa-1, VIa-h and VIc from the rat.

Amino Acid Sequence↗
PubMed1988

Anions induce conformational changes and influence the activity and photoaffinity-labelling by 8-azido-ATP of isolated cytochrome c oxidase.

The biphasic effect of anions on the activity of isolated bovine heart cytochrome c oxidase is paralleled by changes in the visible oxidized spectra, indicating the different conformational changes in the enzyme induced by bromide, chloride, sulphate, phosphate, ADP and ATP. Photoaffinity-labelling of most subunits of the isolated enzyme by low concentrations of 8-azido-[gamma-32P]ATP is strongly increased by ATP, ADP and unlabelled 8-azido-ATP in an unspecific manner. With the reconstituted enzyme less subunits are labelled and this labelling is only little affected by nucleotides. The data suggest a highly dynamic structure for isolated bovine heart cytochrome c oxidase.

Adenosine Triphosphate↗
PubMed1988

Evolution of cytochrome c oxidase.

The current view on the regulatory function of nuclear-encoded subunits of cytochrome c oxidase from higher evolved organisms is presented. The activity of monomeric laurylmaltoside-dissolved, but not of reconstituted cytochrome c oxidase, is strongly affected by anions accompanied by a conformational change of the enzyme, as shown by changed visible spectra. Addition of uncoupler to proteoliposomes induces the same anion sensitivity as obtained with the soluble enzyme, suggesting dissociation of the dimeric membrane-bound enzyme by uncoupler. Nucleotides are suggested to regulate cytochrome c oxidase activity at 3 different sites: 1) Interaction of ATP with a cytosolic site (outside) increases the Km for cytochrome c in the enzyme from bovine heart and Paracoccus denitrificans; 2) binding of ADP at a matrix site decreases, and 3) binding of ATP at another matrix site increases the Km for cytochrome c of the mammalian enzyme.

Amino Acid Sequence↗
PubMed1979

Early molecular events in the interaction of enveloped viruses with cells. I. A fluorescence and radioactivity study.

The fluorescence depolarization of 1,6-diphenyl-hexatriene was used to study the dynamic properties of the hydrophobic regions of the lipid envelopes of ortho- and paramyxoviruses as well as of the Rous sarcoma virus and of the membrane lipids of susceptible and nonsusceptible cells. The systems investigated where active and inactive influenza viruses, and NDV virus acting on chick embryo fibroblasts and Rous sarcoma virus acting on susceptible (C/E) and nonsusceptible (C/B) chicken-cell. Polarization degrees and mean rotational correlation times of DPH embedded in viral lipids were significantly higher than those of DPH in the cell membranes, due to a higher rigidity of the virus envelopes. When suspensions of labelled viruses and unlabelled cells or unlabelled viruses and labelled cells were mixed, a characteristic change of the fluorescence polarization degrees with time was observed. This behaviour was ascribed to label transfer from virus to cell membranes or vice versa. While the rate constants of label transfer from virus to cells and cells to virus were about the same for the penetrating viruses the rate constants of label release from inactive virus to cells were much larger than for the migration in the opposite direction.

Animals↗
PubMed1979

Thermotropic behavior of some fluorodimyristoylphosphatidylcholines.

The thermotropic behavior of three fluorinated phospholipids has been studied by means of high-sensitivity differential scanning calorimetry. The three lipids are 1,2-di(X,X-difluoromyristovyl)phosphatidylcholine with X = 4,8, or 12. The compound with X = 4 has a higher transition temperature than dimyristoylphosphatidylcholine whereas the other two have lower values. All three lipids have transition enthalpies approximately twice that of the unsubstituted lipid. It was found the substituted lipids form strikingly nonideal mixtures with the parent compound. In view of these observations it is evident that results obtained using these or related compounds as probes of bilayer or membrane behavior must be interpreted with due caution. Some of the properties exhibited by geminal fluorine atoms in fluorinated phospholipids appear to be similar to those of cis double bonds in lipids.

Calorimetry↗
PubMed1977

[Study of systolic ventricular volume changes by means of current measurement of contrast media].

Systolic changes of left ventricular volume were estimated after left ventricular contrast injections in dogs by roentgen-videodensitometry with adjustable windows. Good correlations were found between densitometric volume changes and the integral of electromagnetic aortic flow, as measured every 20 msec (r greater than or equal to 0.95 in 118 of 124 systoles analyzed). Videodensitometry avoids the time consuming frame-to-frame analysis with the errors inherent in geometric assumptions in ventricular volume measurements.

Animals↗
PubMedDate not supplied

Cultivation of recombinant baby hamster kidney cells in a fluidized bed bioreactor system with porous borosilicate glass.

Dense cell cultivation of the recombinant cell line BHK 21 pSVIL2 was performed in a fluidized bed bioreactor system containing porous borosilicate glass carriers. Experiments were carried out with different medium formulations for a period of 48 days. Due to an effective immobilization of the cells in the reactor, continuous operation was easy to perform. Maximal cell densities and product yields could be maintained, even when protein-free medium was perfused exceeding 2 reactor volumes per day. Final cell densities of magnitude 7.1 x 10(7) mL-1 intrasphere volume were reached, while the interleukin-2 production rate was 0.70 mg day-1. The cell specific productivity reached a value of 1.3 x 10(-10) mg day-1. The first results were presented with a cell line that grows under glutamine-free medium conditions. The use of a glutamine-free medium for the cultivation of the cells resulted in a drastic decrease in cell metabolism. Furthermore, the amino acids lysine and histidine were produced and secreted into the culture supernatant, although these metabolites normally are considered to be essential for animal cells grown in vitro. However, no lethal effect on the cells has been detected, and the total number of cells in the reactor remained constant. The metabolism of threonine has been detected to be directly dependent on the presence of glutamine. Cells grown in glutamine-free culture medium produced glycine yields 6 times higher than those grown in glutamine-containing medium. A bead-to-bead transfer of the cells has also been detected when the cells immobilized within the intrasphere volume of the borosilicate carriers reached the stationary phase.

Amino Acids↗
PubMedDate not supplied

Age-dependent expression of advanced glycation end product receptor genes in the human heart.

BACKGROUND: Advanced glycation end products (AGEs) are formed by the reaction of sugars and NH2 groups of lysine and arginine residues and have been shown to accumulate in tissues, including the heart, with normal ageing. The interaction of AGEs with their receptors is known to cause changes in cell function, leading, for example, to the production of pro-inflammatory cytokines and free radicals. OBJECTIVE: This study investigated the gene expression of the five known AGE receptors: AGE-R1, AGE-R2, AGE-R3, the scavenger receptor II, and the receptor for AGEs (RAGE) in human heart tissue. METHODS: Tissue samples were taken from the right cardiac auricles from three patient groups: children (2.4 +/- 1.1 years), adults (45.3 +/- 0.8 years) and elderly subjects (76.4 +/- 0.4 years). Analysis of gene expression of the five AGE receptors was performed using the reverse transcription-polymerase chain reaction (RT-PCR) and 18S mRNA levels as loading controls. RESULTS: Our results show an age-dependent upregulation of the genes for AGE-R3 and the scavenger receptor II, but a downregulation for RAGE and no significant differences for AGE-R1 and AGE-R2. CONCLUSION: This study supports a pathophysiological function for AGE receptors such as AGE-R3 and RAGE in the ageing heart.

Adult↗