Biomedical subjects

H Eistetter

Publications and source records attributed to H Eistetter.

6 recordsLinked to original sources

PubMed1994

Competitive antagonism by phenylglycine derivatives at type I metabotropic glutamate receptors.

The metabotropic glutamate receptors (mGluRs) form a family of G-protein-coupled receptors which consists of at least seven members termed mGluR1-mGluR7. These members are classified into subfamilies according to their sequence similarities, signal transduction mechanisms and agonist selectivities. mGluR1 and mGluR5 are coupled to the phosphoinositide hydrolysis/Ca2+ signal transduction and efficiently respond to quisqualate. In this study, we have stably expressed mGluR1 in Chinese hamster ovary cells on which the activation of the phosphoinositide signal transduction pathway was evaluated by means of two methods and their degree of correspondence was analyzed. These two methods involve the Li(+)-dependent accumulation of [3H]inositol-labeled inositol phosphates or the [3H]cytidine-labeled phospholiponucleotide cytidine diphospho (CDP)- diacylglycerol (DAG). The correlation between the two measures was found to be generally uniform for the different agonists evaluated. However, the levels of CDP-DAG were found to be consistently higher. Furthermore, quisqualate showed a differential activity on the two methods behaving as a partial agonist and as a full agonist on the inositol phosphate and the CDP-DAG responses, respectively. On the same cells the activity of a series of carboxyphenylglycines recently described as possible new tools for investigating the role of mGluRs has been evaluated. Three phenylglycine derivatives were tested and found to be competitive antagonists at this mGluR subtype. They inhibited both the phosphoinositide signal transduction pathway and the release of intracellular Ca2+ induced by quisqualate the most potent agonist at mGluR1. The pharmacological nature of these compounds and their relative potencies in antagonizing mGluR1 activation are described.

Aminobutyrates↗

PubMed1990

Lung surfactant: a biotechnological challenge.

The genes for all three of the bona fide surfactant associated proteins have been cloned, allowing their production by recombinant DNA technology. In addition, improved protocols for the isolation of the natural surfactant proteins (NSP) made them available in larger quantities. Whereas, the NSP are often mixtures of allelic variants or functional isomers from gene families, the recombinant proteins (RSP) are obtained as single pure protein species. Antibodies directed against the N/RSP in combination with DNA probes have allowed new approaches to analyze the formation, location, transport, structure and functional capacities of these molecules as well as their interactions with one another and the phospholipids.

Amino Acid Sequence↗

PubMed1988

Macromolecular organization of natural and recombinant lung surfactant protein SP 28-36. Structural homology with the complement factor C1q.

The macromolecular structure of the pulmonary surfactant apolipoprotein SP 28-36 has been determined. For SP 28-36 isolated from dog lung lavage, a flower bouquet-like hexameric structure with six globular domains connected by short stalks to a common stem was revealed by electron microscopy, using the rotary shadowing technique. This structure is very similar to that published for the subcomponent C1q of the first component of complement C1. The lavage material was compared with the homologous human recombinant SP 28-36 by the same technique. Mostly smaller aggregates like di-, tri- and tetramers as well as very high aggregates were observed. Mild reduction of the recombinant material revealed the lollipop-shaped monomers composed of a globular domain and a tail with a discrete kink in the middle portion. The collagenous nature of the tail was demonstrated by circular dichroism spectroscopy. This implies that the mammalian expression system assembles the monomeric subunits correctly. Assembly into the hexameric structures, however, does not proceed quantitatively.

Animals↗

PubMed1987

The structure of cell adhesion molecule uvomorulin. Insights into the molecular mechanism of Ca2+-dependent cell adhesion.

We have determined the amino acid sequence of the Ca2+-dependent cell adhesion molecule uvomorulin as it appears on the cell surface. The extracellular part of the molecule exhibits three internally repeated domains of 112 residues which are most likely generated by gene duplication. Each of the repeated domains contains two highly conserved units which could represent putative Ca2+-binding sites. Secondary structure predictions suggest that the putative Ca2+-binding units are located in external loops at the surface of the protein. The protein sequence exhibits a single membrane-spanning region and a cytoplasmic domain. Sequence comparison reveals extensive homology to the chicken L-CAM. Both uvomorulin and L-CAM are identical in 65% of their entire amino acid sequence suggesting a common origin for both CAMs.

Amino Acid Sequence↗

PubMed1985

The in vitro development of blastocyst-derived embryonic stem cell lines: formation of visceral yolk sac, blood islands and myocardium.

The in vitro developmental potential of mouse blastocyst-derived embryonic stem cell lines has been investigated. From 3 to 8 days of suspension culture the cells form complex embryoid bodies with endoderm, basal lamina, mesoderm and ectoderm. Many are morphologically similar to embryos of the 6- to 8-day egg-cylinder stage. From 8 to 10 days of culture about half of the embryoid bodies expand into large cystic structures containing alphafoetoprotein and transferrin, thus being analagous to the visceral yolk sac of the postimplantation embryo. Approximately one third of the cystic embryoid bodies develop myocardium and when cultured in the presence of human cord serum, 30% develop blood islands, thereby exhibiting a high level of organized development at a very high frequency. Furthermore, most embryonic stem cell lines observed exhibit similar characteristics. The in vitro developmental potential of embryonic stem cell lines and the consistency with which the cells express this potential are presented as aspects which open up new approaches to the investigation of embryogenesis.

Animals↗

PubMed1983

Phosphorylation of endogenous proteins of cilia from Paramecium tetraurelia in vitro.

Several endogenous substrate proteins of cilia from axenically grown Paramecium tetraurelia were phosphorylated in vitro by inherent protein kinases (PKs). Labeling was stimulated by cAMP and to a lesser extent by cGMP. ATP breakdown was most rapid in cilia and subciliary fractions. Using multiple substrate additions during incubations it was shown that phosphorylation was almost completed within 30 s. Very little dephosphorylation by phosphoprotein phosphatases occurred during 5 min of incubation. Proteins of molecular weight of 103 000 and 46 000 were shown to be particularly associated with axonemal structures of the cilia. No distinct differences in phosphorylation patterns were apparent in ciliary membrane vesicles of low and high buoyant density, which exhibit differential enzyme patterns. cAMP receptor proteins were identified by use of the photoaffinity label 8-azido-[32P]cAMP. Receptor proteins with apparent molecular weights of 43 000, 39 000, 37 000, 31 000 and 30 000 were probably related to the regulatory subunits of cAMP-dependent protein kinases as evidenced by inhibition of incorporation of the photoaffinity label by low concentrations of cAMP. Tagging of a protein of 85 000 molecular weight was specifically inhibited by cGMP, thus in all likelihood it corresponded to a cGMP-dependent protein kinase. Corresponding autophosphorylated protein bands were observed with gamma-[32P]ATP. A functional role for protein phosphorylation in cilia of Paramecium remains to be established.

Animals↗