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Biomedical subjects

C Dietrich

Publications and source records attributed to C Dietrich.

At least 55 records · Page 3Linked to original sources
PubMed1995

The actin-binding protein hisactophilin binds in vitro to partially charged membranes and mediates actin coupling to membranes.

The interaction of the actin-binding protein hisactophilin from Dictyostelium discoideum amoebae to partially charged lipid membranes composed of mixtures of L-alpha-dimyristoylphosphatidylcholine (DMPC) with L-alpha-dimyristoylphosphatidylglycerol (DMPG) and L-alpha-phosphatidylinositol 4,5-bisphosphate (PIP2) is studied by film balance experiments, microfluorescence, and lateral diffusion measurements at low ionic strengths (approximately 20 mM). Excess surface concentrations and adhesion energies of the protein are evaluated by the application of Gibbs law of surface excess as a function of charged lipid content. Protein expressed in E. coli lacking a myristic acid chain (EC-HIS) and natural protein with a fatty acid (DIC-HIS) isolated from Dictyostelium cells are compared. For mixtures of DMPG and DMPC, protein binding leads to an increase in lateral pressure of the monolayer (at constant area) and causes strong lipid immobilization pointing to partial penetration of the protein into the lipid layer. The natural protein causes a much stronger immobilization than does EC-HIS. For a given bulk concentration, the adsorbed protein/lipid molar ratio increases with the molar fraction chi PG of charged lipid but saturates at about 50 mol% of DMPG. Natural hisactophilin (DIC-HIS) binding to PIP2-containing monolayers is purely electrostatic at low bulk concentration cb, and protein penetration dominates only at cb > 68 nM. Fluorescence experiments demonstrate that the natural protein (DIC-HIS) can mediate the binding of monomeric actin or very small oligomers to membranes, showing that the adsorbed protein remains functional. In contrast, the recombinant hisactophilin (EC-HIS) can mediate only the membrane coupling of larger actin structures.

Actins↗
PubMed1995

Molecular organization of histidine-tagged biomolecules at self-assembled lipid interfaces using a novel class of chelator lipids.

In molecular biology, the expression of fusion proteins is a very useful and well-established technique for the identification and one-step purification of gene products. Even a short fused sequence of five or six histidines enables proteins to bind to an immobilized metal ion chelate complex. By synthesis of a class of chelator lipids, we have transferred this approach to the concept of self-assembly. The specific interaction and lateral organization of a fluorescent fusion molecule containing a C-terminal oligohistidine sequence was studied by film balance techniques in combination with epifluorescence microscopy. Due to the phase behavior of the various lipid mixtures used, the chelator lipids can be laterally structured, generating two-dimensional arrays of histidine-tagged biomolecules. Because of the large variety of fusion proteins already available, this concept represents a powerful technique for orientation and organization of proteins at lipid interfaces with applications in biosensing, biofunctionalization of nanostructured interfaces, two-dimensional crystallization, and studies of lipid-anchored proteins.

Amines↗
PubMed1995

Charge determination of membrane molecules in polymer-supported lipid layers.

A method for two-dimensional micro-electrophoresis and charge determination of fluorescence-labeled membrane molecules in lipid layers is presented. Therefore, the labeled molecules are dissolved in a lipid monolayer which acts as a fluid matrix. The essential part of the sample preparation is an aqueous polymer film composed of agarose onto which the layer is transferred by Langmuir-Blodgett technique. The induced force of an applied electric field leads to a drift of the charged fluorescent molecules. The mobility is determined by an analysis of the steady-state bleach profile which is produced by continuous fluorescence micro-photolysis of a rectangular area of the monolayer. Testing a variety of amphiphilic molecules, measurements yielded values of zero, plus or minus one elementary net charge within a margin of error. The experimental set-up described here can be used for lateral separation, enrichment and isoelectric focusing of membrane components.

Biopolymers↗
PubMed1995

Prejunctional M1 and postjunctional M3 muscarinic receptors in the circular muscle of the guinea-pig ileum.

The effects of subtype-selective muscarinic receptor antagonists on electrically evoked release of acetylcholine and muscle contraction were compared in circular muscle preparations of the guinea-pig ileum. Incubation of the preparation with [3H]choline resulted in the formation of [3H]acetylcholine. Electrical stimulation caused the release of [3H]acetylcholine which was abolished by tetrodotoxin and omission of calcium from the medium. 5-Hydroxytryptamine (10 microM) and the nicotinic agonist 1,1-dimethyl-4-phenyl-piperazinium (300 microM) did not change acetylcholine release. The muscarinic antagonists pirenzepine (M1 selective), AF-DX 116 (M2 selective) and hexahydrosiladifenidol (M3 selective) caused concentration-dependent increases in the evoked release of acetylcholine, and inhibitions of the circular muscle contraction. The postjunctional affinity constants (pA2 values) obtained for hexahydrosiladifenidol (8.06), pirenzepine (6.95) and AF-DX 116 (6.60) identified the muscular receptor as an M3 subtype. Pirenzepine was more potent in facilitating the evoked release than hexahydrosiladifenidol and AF-DX 116. These findings suggest that the release of acetylcholine in the circular muscle is inhibited by M1 muscarinic autoreceptors whereas muscle contraction is mediated by M3 receptors.

Acetylcholine↗
PubMed1994

Insertion of filamin into lipid membranes examined by calorimetry, the film balance technique, and lipid photolabeling.

The interaction of the actin-binding protein filamin with mixtures of zwitterionic and anionic phospholipids (DMPC, DMPG, PC, PS) was studied in reconstituted lipid monolayers and bilayers. Protein-lipid interactions were investigated by differential scanning calorimetry, the film balance technique, and hydrophobic photoradiolabeling. For calorimetric assays, multilamellar vesicles (MLVs) and large unilamellar vesicles produced by the extrusion technique (LUVETs) were used. With MLVs, filamin induced a pronounced drop in phase transition cooperativity. Mixed DMPC/DMPG LUVETs showed a linear decrease of the main phase transition enthalpy and a significant shift in temperature for the solidus and liquidus lines with increasing mole fractions of reconstituted filamin. The insertion of native filamin into uncharged and negatively charged lipid monolayers was measured in time/area diagrams with the film balance technique. Finally, we have newly synthesized a highly sensitive lipid analogue, [125]TID-PC/16, which selectively labels membrane-embedded hydrophobic domains of proteins, and which proved to label filamin, supporting evidence that this protein partially inserts into the hydrophobic domain of liposomes.

Calorimetry, Differential Scanning↗
PubMed1994

Karyotypic characterization of bronchial large cell carcinomas.

Cytogenetic analysis of short-term cultures from 26 primary bronchial large cell carcinomas and 1 metastasis from a primary large cell carcinoma revealed clonal chromosome abnormalities in 20 tumors and a normal karyotype in 6. No outgrowth was obtained in 1 case. Simple aberrations were present in 3 tumors; in 1, the only change was a reciprocal translocation between chromosomes 1 and 6, in another the sole anomaly was a supernumerary marker ring chromosome and in a third loss of the Y chromosome was the only clonal change. The remaining 17 tumors had complex karyotypes. The chromosomes most frequently involved in structural rearrangements were chromosomes 1, 2, 3, 5, 6, 7, 8, 10, 11, 13, 14 and 17. The bands most frequently affected were 1q11-12, 1p13, 7q11, and 17p11-13. The rearrangements led to repeated losses of 1p, 1q, 3p, 6q, 7q and 17p and gains of 5q and 7p. The emerging karyotypic picture of large cell lung carcinomas indicates more similarities with adenocarcinomas than with other pathologic subgroups of lung cancer.

Aged↗
PubMed1993

Interaction of NBD-talin with lipid monolayers. A film balance study.

Fluorescently labelled smooth muscle talin like native talin interacts with negatively or partly negatively charged lipid monolayers. This was measured in time/area diagrams using the film balance technique combined with fluorescence imaging after double photolabelling of talin and phospholipids.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1993

Functional relevance of presynaptic muscarinic autoreceptors.

Pre- and postsynaptic muscarinic receptors have been characterized in the isolated trachea and ileal circular muscle of the guinea pig. The muscarinic autoreceptors mediating inhibition of acetylcholine release in the circular muscle belong to the M1 subtype, whereas those inhibiting acetylcholine release in the trachea are M2 or M4 receptors. In both tissues the postsynaptic muscarinic receptors are M3 receptors. Blockade of the autoreceptors by selective M1 and M2/M4 receptor antagonists leads to facilitation of cholinergic neurotransmission.

Animals↗
PubMed1993

Recombinations of chromosomal bands 6p21 and 14q24 characterise pulmonary hamartomas.

Cytogenetic analysis of short-term cultures from seven pulmonary hamartomas revealed an abnormal karyotype in six of them. The most characteristic aberration was an exchange of material between 6p21 and 14q24, found in three tumours. Abnormalities of either 6p or 14q were seen in another two hamartomas. Other regions that were rearranged more than once were 12q (three times) and 17p (twice), sometimes in exchange with 6p or 14q and giving rise to complex derivative chromosomes. Only one tumour had aberrations that did not involve 6p, 12q, 14q, or 17p. These results-together with the data on three previously reported pulmonary hamartomas, two of which also had t(6;14)-show that recombinations between 6p21 and 14q24 are common, and hence probably pathogenetically important. The data support the view that these tumours are genuine neoplasms rather than developmental anomalies. The coexistence of a common 14q24 breakpoint in uterine leiomyomas and pulmonary hamartomas indicates that a gene important in the genesis of both tumours exists in this band.

Adult↗
PubMed1989

Cytogenetic studies on three pheochromocytomas derived from patients with von Hippel-Lindau syndrome.

Chromosomal analyses of three pheochromocytomas from patients with von Hippel-Lindau syndrome are reported. One pheochromocytoma revealed a normal karyotype, another tumor showed a trisomy 7 as the only chromosomal abnormality, whereas in a further sample a polyclonal chromosome constitution was detected. In addition to a normal 46,XX cell line, four distinct chromosomally abnormal cell lines could be identified. One cell line revealed partial trisomy for the long arm of chromosome 1 and additionally exhibited the phenomenon of telomeric association. Most interestingly, three further cell clones showed rearrangements of chromosome 3 including the region where the von Hippel-Lindau gene was mapped; three rearrangements resulted in a partial or total trisomy of 3p. Our findings are discussed in relation to previously reported cytogenetic and molecular results regarding von Hippel-Lindau syndrome.

Adrenal Gland Neoplasms↗
PubMed1988

Light-induced phosphoinositide degradation and light-induced structural alterations in the rat retina are enhanced after chronic lithium treatment.

In the rat retina, light-induced break down of polyphosphoinositides and structural alterations of photoreceptor outer segment disk-membranes were enhanced by chronic lithium treatment at doses equivalent to therapeutic levels in humans. Furthermore, the recovery of phosphoinositide baseline levels after light exposure was delayed in lithium treated retinas. Light and lithium may thus affect phospholipid membranes in the retina. Initial processes in the pathogenesis of light damage in the retina are largely unknown to date. The hydrolysis of polyphosphoinositides may possibly constitute such an initial event.

Animals↗
PubMed1988

Increased amounts of small polydisperse circular DNA (spcDNA) in angiofibroma-derived cell cultures from patients with tuberous sclerosis (TS)

Much greater amounts of small polydisperse circular DNA (spcDNA) have been detected, in cell cultures derived from angiofibromas of six patients with tuberous sclerosis (TS) than in those from the skin of these patients or from the skin of 11 healthy donors. This observation could be confirmed by spreading the DNA of appropriate fractions from CsCl density gradients. The findings suggest the existence of a relationship between the chromosomal instability observed in angiofibroma cultures and the mobilization of spcDNA.

Adult↗
PubMed1988

[Lithium-induced lesions in the rat retina--potentiation by light].

The treatment of manic-depressive patients with lithium salts is a widespread procedure. Ocular side effects of this therapy comprise changes in electrophysiological and psychophysical parameters. Photochemical damage to the human and animal retina is a widely recognized and investigated phenomenon. The present paper describes lithium-induced changes in the albino rat retina on a morphological and biochemical level that are significantly enhanced by acute light exposure in an intensity-dependent manner. Preliminary biochemical data reveal an increase in phosphatidylinositol metabolites. As a clinical consequence of the study the authors advocate careful ophthalmological examination of chronically lithium-treated patients, especially those suffering from retinal degeneration or who are exposed to light of higher than normal intensity.

Animals↗
PubMed1988

Morphology and time-course of defined photochemical lesions in the rabbit retina.

The present study demonstrates an experimental set-up to study light injury with defined parameters including retinal irradiance levels and spectral composition of the damaging light. The time-course of acute morphological changes at constant light intensity and increasing exposure durations (from 5-30 minutes) was evaluated, the wavelength of the damaging light being 400-550 nm. Pigment epithelial lesions appeared already after 5 minutes, and rod outer segment membrane disruptions after 15-20 minutes of light exposure. Striking was the observation of disruption and vesiculation of disk membranes at the base of rod outer segments. This "clear zone" was consistently observed beginning after twenty minutes of light exposure. The comparison of morphological changes in pigmented and albinotic eyes revealed no essential differences. This result confirms the observations of other laboratories that pigment epithelial melanin neither protects against nor promotes light damage to a significant extent. Long-term changes after light exposure revealed pigment epithelial lesions and rod outer segment disruptions, followed by macrophage invasion and pigment epithelial proliferation with subsequent loss of photoreceptor cells.

Albinism↗