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J Andrä

Publications and source records attributed to J Andrä.

At least 19 recordsLinked to original sources
PubMed2004

Structural polymorphism and endotoxic activity of synthetic phospholipid-like amphiphiles.

The physicochemical characteristics and in vitro biological activity of various synthetic hexaacyl phospholipid dimers were compared with the respective behavior of bacterial endotoxins (lipopolysaccharide, LPS). The structural variations of the synthetic amphiphiles include different stereochemical (R,S) configurations about their ester- and amide-linkages for the acyl chains and differences in the length of the serine backbone spacer. The temperature of the gel to liquid crystalline phase transition of the acyl chains (T(c)) lies between 10 and 15 degrees C for the compounds with the shortest backbone and decreases rapidly for the compounds with longer backbones. The phase transition enthalpies (8-16 kJ x mol(-1)) are considerably lower than those of lipid A from hexaacyl endotoxins (28-35 kJ x mol(-1)). In contrast, the dependence of T(c) on Mg(2+) and water content shows a behavior typical for endotoxins: a significant increase with increasing Mg(2+) and decreasing water concentrations. The aggregate structure is sensitively dependent not only on the length of the backbone spacer but also on the different stereochemical variations. It can be directly correlated with the biological activity of the compounds. Thus, as with natural lipid A, the capacity to induce cytokine production in mononuclear cells is directly related to the affinity to form nonlamellar cubic or inverted hexagonal H(II) aggregate structures. Together with the data on the transport and intercalation of the dimers into phospholipid liposomes mediated by the lipopolysaccharide-binding protein (LBP), our conformational concept of endotoxicity and cell activation can be applied to these non-LPS structures: endotoxically active compounds incorporate into membranes of immune cells and cause conformational changes at the site of signaling proteins such as Toll-like receptors or K(+)-channels due to their conical molecular shape.

Animals↗
PubMed2001

Cecropins, antibacterial peptides from insects and mammals, are potently fungicidal against Candida albicans.

Natural products are the major source of lead compounds for drugs against human pathogens. Among the first natural peptides from animals for which a potent antibacterial activity has been recognized were the cecropins. The 30- to 40-residue alpha-helical peptides display their activity by permeabilizing the membranes of bacteria. Although originally isolated from insect hemolymph, a structural and functional correlate was also found in a mammal. Here, we report on the finding that cecropin A and B from the silk moth Cecropia as well as the porcine cecropin P1 are capable of inhibiting the growth of and to kill yeast-phase Candida albicans. The peptides were tested in radial diffusion and microbroth dilution assays. They displayed potent activity against a clinical isolate as well as against defined culture strains of the pathogenic yeast but are of exceedingly low cytotoxicity towards the human cell line Jurkat. The candidacidal properties of the intensely studied molecules known to be highly active against Gram-positive and Gram-negative bacteria may renew the interest in these natural broad-spectrum peptide antibiotics and their limited cytotoxicity to human cells may be exploited for the development of topical therapeutics against pathogens resistant to classical antibiotics.

Animals↗
PubMed1999

Candidacidal activity of shortened synthetic analogs of amoebapores and NK-lysin.

Natural antimicrobial peptides and synthetic analogs thereof have emerged as compounds with potentially significant therapeutical application against human pathogens. Amoebapores are 77-residue peptides with cytolytic and antibacterial activity considered to act by forming ion channels in cytoplasmic membranes of the victim cells. A functionally and structurally similar peptide named NK-lysin exists in mammalian lymphocytes. Several synthetic analogs of amoebapores and NK-lysin, which are substantially reduced in size compared to the parent molecules, were tested for their ability to inhibit the growth of and to kill Candida albicans. Some of the peptides displayed potent activity against a clinical isolate as well as against defined culture strains. Among the most active peptides found are some shortened substitution analogs of amoebapore C and a cationic core region of NK-lysin. As these peptides are also highly active against Gram-positive and Gram-negative bacteria but are of low cytotoxicity towards a human keratinocyte cell line they may provide promising templates for the design of broad-spectrum peptide antibiotics.

Amino Acid Sequence↗
PubMed1996

Shortened amoebapore analogs with enhanced antibacterial and cytolytic activity.

Amoebapores are cytolytic peptides of Entamoeba histolytica which function by the formation of ion channels in target cell membranes. Three isoforms (amoebapore A, B, and C) exist in amoebic cytoplasmic granules. They are composed of 77 amino acid residues arranged in four alpha-helical domains. In order to analyze the structure-function relationships, 15 synthetic peptides of 24-25 residues were constructed based on the assumption that the third helix is the membrane-penetrating domain and on the previous finding that positively charged residues are significant for activity. Activity of these short versions of amoebapores was determined towards artificial and natural targets, such as liposomes, bacteria, erythrocytes and a human tumor cell line. It was found that some of the novel peptides were highly active and showed a broader activity spectrum compared to the parent molecules.

Amino Acid Sequence↗
PubMed1994

Pore-forming peptide of Entamoeba histolytica. Significance of positively charged amino acid residues for its mode of action.

Amoebapore is a 77-residue pore-forming peptide from Entamoeba histolytica with antibacterial and cytolytic properties. It contains eight lysine residues and one histidine residue. Chemical modifications of amoebapore with various reagents affecting either both types of cationic residues or lysine and histidine residues separately resulted in virtually complete loss of pore-forming activity. The activity was restored by reversal of modifications. Whereas amoebapore was no longer capable of binding to phospholipid vesicles when its lysine residues were modified, the modification of the single histidine primarily affected oligomerization of the peptide upon membrane association.

Amino Acid Sequence↗
PubMed1994

Cytolytic and antibacterial activity of synthetic peptides derived from amoebapore, the pore-forming peptide of Entamoeba histolytica.

The pore-forming peptide amoebapore is considered part of the cytolytic armament of pathogenic Entamoeba histolytica. Amoebapore is composed of 77 amino acid residues arranged in four alpha-helical domains. For structure-function analysis, synthetic peptides were constructed corresponding to these four domains: H1 (residues 1-22), H2 (25-39), H3 (40-64), and H4 (67-77). The peptides H1 and H3, representing two highly amphipathic alpha-helical regions of amoebapore, possessed pore-forming activity. Peptide H3 displayed cytolytic and antibacterial functions similar to those of natural amoebapore. The most potent antibacterial activity and the broadest activity spectrum were expressed by H1-Mel, a hybrid molecule composed of the N-terminal alpha-helix of amoebapore and the C-terminal hexapeptide of melittin from the venom of Apis mellifera.

Amino Acid Sequence↗
PubMed1994

Amoebapores, a family of membranolytic peptides from cytoplasmic granules of Entamoeba histolytica: isolation, primary structure, and pore formation in bacterial cytoplasmic membranes.

Three peptides with pore-forming activity were isolated from the cytoplasmic granules of pathogenic Entamoeba histolytica by acidic extraction, gel filtration and reversed-phase high-performance liquid chromatography. Partial amino acid sequence analysis of the three active peptides revealed that the most abundant of them was amoebapore and the other two were isoforms thereof. Cloning and sequencing of genomic DNA resolved the amino acid sequence of the two newly recognized peptides. The three peptides designated amoebapores A, B and C were found to have the same molecular size but to differ markedly in their primary structure, although all six cysteine residues are conserved. Despite sequence divergence, structural implications predict for the three peptides a similar amphipathic alpha-helical conformation stabilized by disulphide bonds. All three isoforms exhibit pore-forming activity toward lipid vesicles, but they differ in their kinetics. They also are capable of perturbing the integrity of bacterial cytoplasmic membranes and thereby kill Gram-positive bacteria. The amoebapores represent a distinct family of membrane-active peptides that may function intracellularly as antimicrobial agents but may also confer cytolytic activity on the parasite.

Amino Acid Sequence↗
PubMed1992

[Histochemical investigations on the localization of acetylcholinesterase in the kidney of selected vertebrates].

The light and electron microscopical localization of AChE activity in the kidney of selected vertebrates was studied using the method of Karnovsky and Roots (1964) for light microscopy and the modification of the Koelle and Friedenwald's technique according to Tsuji (1974, 1984) for electron microscopy. AChE activity could be demonstrated light microscopically mainly within the glomeruli of some mammals (golden hamster, mouse, rat) and non-mammalian vertebrates (carp, frog). No activity was found in the glomeruli of guinea pig, of chicken and tortoise. In the mammalians, the strongest AChE activity could be demonstrated in the guinea pig, the lowest in the rat. A strong AChE enzyme activity was also detected within the interlobular arteries and the cells of Bowman's capsule. With the electron microscopical method AChE activity was demonstrated in mesangial cells and endothelial cells of the glomeruli (golden hamster and carp) and in the cells of Bowman's capsule (carp). Reaction product was localized within the cisterns of endoplasmic reticulum and the perinuclear space (nuclear envelope). A high amount of electron opaque material could be observed in the cells of Bowman's capsule and their lamina basalis. The functional significance of the localization of AChE activity in the glomeruli will be discussed.

Acetylcholinesterase↗
PubMed1988

A comparison of the localization of acetylcholinesterase in the rat brain as demonstrated by enzyme histochemistry and immunohistochemistry.

The localization of acetylcholinesterase (AChE) as revealed either by enzyme-histochemical or by immunohistochemical methods was compared in distinct regions of the rat brain. In general, the localization of AChE observed was nearly the same, whether revealed by histochemical demonstration of its catalytic activity or by immunohistochemical detection of the enzyme molecule itself, in all regions investigated. Penetration problems of the antibodies, however, arose on strong myelin sheaths of the facial nerve, for instance, where no immunohistochemical staining was found though there was a relatively strong histochemical reaction. These problems could be partly solved by increasing the normal concentration of Triton X-100 added to the immunohistochemical solutions (0.1%) to 2.5%. Furthermore, it seems that sites containing low amounts of AChE could be better detected by the enzyme-histochemical method, whereas the depiction of structures (particularly of nerve fibres) was somewhat sharper with the immunohistochemical method.

Acetylcholinesterase↗
PubMed1986

A histochemical method for the demonstration of acetylcholinesterase activity using semipermeable membranes.

The "direct coloring" thiocholine method of Karnovsky and Roots (1964) for the demonstration of acetylcholinesterase (AChE) activity was modified and adapted to the technique of semipermeable membranes. In this way it is possible to demonstrate histochemically both the bound as well as the soluble part of AChE activity. The localization of the reaction product is very distinct. Microdensitometric investigations of results of this method showed a linear increase of the amount of reaction product up to an incubation time of 180 min and section thickness up to 24 micron. The medium supplemented with buffer (instead of agar) can be used for the demonstration of AChE activity in cryostat sections adherent to slides and is also very suitable for the detection of multiple forms of AChE in polyacrylamide or agarose gels.

Acetylcholinesterase↗
PubMed1986

[Quantitative histochemical investigations on the demonstration of soluble and membrane bound acetylcholinesterase in the optic tectum of the rudd (Scardinius erythrophthalmus)].

With the aid of the method of Karnovsky and Roots (1964) which was adapted to the semi-permeable membrane technique and a scanning recording method the relative activity of soluble and membrane bound AChE as well as the influence of fixation with 5% paraformaldehyde on the enzyme activity was investigated quantitative-histochemically in the tectum opticum of the rudd. Approximately 38% of the AChE activity which can be demonstrated in the whole tectum opticum on native untreated cryostat sections are puffer-soluble and only 68% are detectable after fixation. The influence of both puffer and fixation pretreatment is different in the several layers of this brain structure.

Acetylcholinesterase↗
PubMed1985

Quantitative aspects of cytochemical methods for acetylcholinesterase studied with a cytochemical model system.

A model system of polyacrylamide films containing the Triton extract of rat brain homogenate was applied to investigate quantitatively some aspects of three methods for the cytochemical demonstration of acetylcholinesterase activity (Lewis 1961; Karnovsky and Roots 1964; Tsuji 1974). Biochemical determinations showed that about 90% of the acetylcholinesterase activity originally present in the Triton extract were still detectable in the films. The relationship of the formation of cuprous thiocholine iodide in the case of the methods of Lewis (1961) or Tsuji (1974) and of cupric ferrocyanide at the reaction of Karnovsky and Roots (1964) to either enzyme concentration or incubation time were tested in detail. The results showed that for the method of Tsuji and, with some restrictions, also for the method of Karnovsky and Roots a linearity exists in these two respects. In the case of the Lewis technique, an approximate linearity between the amount of reaction product and incubation time could only be found from 90 min onward, but no linearity was detected in relation to the enzyme concentration. At low enzyme concentrations, too little white precipitate was formed in comparison to higher ones. Therefore it is suggested that this technique, as compared to the methods of Tsuji and Karnovsky and Roots, probably is less suitable as a quantitative cytochemical method.

Acetylcholinesterase↗
PubMed1982

[Histochemical and biochemical investigations of the hippocampus and neocortex of the wistar rat. III. Electron-microscopic investigations on the localization of non-specific esterases in the hippocampus (author's transl)].

This report describes the ultrastructural localization of the non-specific esterases in the pyramidal cells of the CA3-region of rat hippocampus. The use of specific inhibitors allowed the differentiation between aryl-, carboxyl- and acetylesterases. The thiolacetic acid reaction at pH = 5.2 and 7.0 proved to be a favourable method for the conditions of the hippocampus. Liver tissue served for control purposes. In the pyramidal cells carboxylesterase could be demonstrated on membranes and cisternes of the endoplasmic reticulum on polysomes and in the nuclear envelope. Arylesterase was localized in numerous synaptic vesicles and in the myeline sheath of axons. In lysosomes and in mitochondria an esterase activity was demonstrable, which behaved like an acetylesterase. In the hippocampus carboxylesterase could be shown only at pH = 7.0, whereas in liver this enzyme also give a clear reaction at pH = 5.2. Aryl- and acetylesterase reacted at both pH-ranges in the hippocampus. Biochemical investigations showed that the tissue pretreatment, which is necessary for the ultrahistochemical demonstration of nonspecific esterases considerable decreased the enzyme activity. Formaldehyde and glutaraldehyde have thereby a different action on the several esterase types.

Animals↗