Biomedical subjects

R Hertle

Publications and source records attributed to R Hertle.

11 recordsLinked to original sources

PubMed2004

Tyramine functions as a toxin in honey bee larvae during Varroa-transmitted infection by Melissococcus pluton.

From wounds of honey bee pupae, caused by the mite Varroa destructor, coccoid bacteria were isolated and identified as Melissococcus pluton. The bacterial isolate was grown anaerobically in sorbitol medium to produce a toxic compound that was purified on XAD columns, gelfiltration and preparative HPLC. The toxic agent was identified by GC-MS and FTICR-MS as tyramine. The toxicity of the isolated tyramine was tested by a novel mobility test using the protozoon Stylonychia lemnae. A concentration of 0.2 mg/ml led to immediate inhibition of mobility. In addition the toxicity was studied on honey bee larvae by feeding tyramine/water mixtures added to the larval jelly. The lethal dosis of tyramine on 4-5 days old bee larvae was determined as 0.3 mg/larvae when added as a volume of 20 microl to the larval food in brood cells. Several other biogenic amines, such as phenylethylamine, histamine, spermine, cadaverine, putrescine and trimethylamine, were tested as their hydrochloric salts for comparison and were found to be inhibitory in the Stylonychia mobility test at similar concentrations. A quantitative hemolysis test with human red blood cells revealed that tyramine and histamine showed the highest membranolytic activity, followed by the phenylethylamine, trimethylamine and spermine, while the linear diamines, cadaverine and putrescine, showed a significantly lower hemolysis when calculated on a molar amine basis. The results indicate that tyramine which is a characteristic amine produced by M. pluton in culture, is the causative agent of the observed toxic symptoms in bee larvae. Thus this disease, known as European foulbrood, is possibly an infection transmitted by the Varroa destructor mite.

Animals↗

PubMed2002

Serratia marcescens hemolysin (ShlA) binds artificial membranes and forms pores in a receptor-independent manner.

Both the inactive and active conformations of the hemolysin/cytolysin of Serratia marcescens (ShlA) binds membranes of erythrocytes, but only active ShlA is able to form pores. ShlA is unable to lyse prokaryotic membranes. To determine the receptors of the binding and pore-forming domains of active cytolysin on eukaryotic membranes, artificial large unilamellar vesicles (LUVs) of various membrane compositions were examined. In the current study, it is shown that significant pore formation and lysis was achieved with binary phosphatidylcholine/phosphatidylserine (PS) liposomes. No proteinaceous receptor was needed for either binding or pore formation by ShlA. Membrane integration and pore-forming activity were enhanced by addition of phosphatidylethanolamine. Phosphatidylserine is negatively charged at physiologic pH and is almost absent in prokaryotic membranes. Hence, membrane binding and insertion of ShlA are highly dependent on phosphatidylserine, which targets the toxic activity to eukaryotic cell membranes without any need of a proteinaceous receptor. This may explain why prokaryotic membranes were found to be resistant against ShlA in a previous study.

Bacterial Proteins↗

PubMed2001

Dual-function vaccine for Pseudomonas aeruginosa: characterization of chimeric exotoxin A-pilin protein.

Pseudomonas aeruginosa is the major infectious agent of concern for cystic fibrosis patients. Strategies to prevent colonization by this bacterium and/or neutralize its virulence factors are clearly needed. Here we characterize a dual-function vaccine designed to generate antibodies to reduce bacterial adherence and to neutralize the cytotoxic activity of exotoxin A. To construct the vaccine, key sequences from type IV pilin were inserted into a vector encoding a nontoxic (active-site deletion) version of exotoxin A. The chimeric protein, termed PE64Delta553pil, was expressed in Escherichia coli, refolded to a near-native conformation, and then characterized by various biochemical and immunological assays. PE64Delta553pil bound specifically to asialo-GM1, and, when injected into rabbits, produced antibodies that reduced bacterial adherence and neutralized the cell-killing activity of exotoxin A. Results support further evaluation of this chimeric protein as a vaccine to prevent Pseudomonas colonization in susceptible individuals.

ADP Ribose Transferases↗

PubMed2000

Two-step fast protein liquid chromatographic purification of the Serratia marcescens hemolysin and peptide mapping with mass spectrometry.

The pore forming toxin of Serratia marcescens (ShlA) is secreted and activated by an outer membrane protein (ShlB). Activation of inactive ShlA (termed ShlA*) by ShlB is dependent on phosphatidylethanolamine (PE). Activation may be a covalent modification of ShlA. To test this hypothesis, the responsible activation domain (in the N-terminal 255 amino acids of ShlA) was isolated from whole bacteria with 8 M urea in an inactive form (ShlA-255*) and from the culture supernatant in an active form (ShlA-255), followed by a two-step purification by anion-exchange chromatography and gel permeation chromatography. Comparison of a tryptic peptide map of both forms with subsequent electrospray mass spectrometry (ES-MS) and sequencing by tandem ES-MS revealed no modification. These data imply that ShlB presumably imposes a conformation on ShlA-255 that triggers activity.

Amino Acid Sequence↗

PubMed2000

Serratia type pore forming toxins.

The Serratia marcescens hemolysin represents a new type of hemolysin and has been studied in great molecular detail with regard to structure, activation and secretion. It has nothing in common with the pore forming toxins of E. coli type (RTX toxins), the Staphylococcus aureus alpha-toxin or the thiol activated toxin of group A beta-hemolytic streptococci (Streptolysin O). Studies on erythrocytes, eukaryotic cells and artificial black lipid membranes, have shown that the mechanism of pore formation of ShlA is different form other pore forming toxins. The S. marcescens hemolysin proteins ShlB and ShlA exhibit protein sequence homologues in Proteus mirabilis, Haemophilus ducreyi, Edwardsiella tarda and Erwinia chrysantemi. Furthermore, sequence motifs present in ShlA and Shlb have been shown to be important for activity and secretion of the S. marcescens hemolysin. Thus, the S. marcescens hemolysin forms the prototype of a new class of hemolysins and of a new secretory mechanism. The uniqueness of this new mechanism is underlined by the fact that activation of ShlA by ShlB strictly requires phosphatidylethanolamine as a cofactor. New data implicate a conformational change in ShlA during activation. In addition, ShlA not only forms pores in erythrocytes but also in fibroblasts and epithelial cells. The cytotoxic action of ShlA is mainly determined by lysis of infected cells in vitro. In sublytic doses, as will normally be the situation in vivo, ShlA exerts additionally effects which are currently under investigation. The knowledge of the structure, activation, secretion and mode of action of S. marcescens hemolysin has implications for proteins, related in sequence or in mode of secretion and activation.

Animals↗

PubMed1999

Cytotoxic action of Serratia marcescens hemolysin on human epithelial cells.

Incubation of human epithelial cells with nanomolar concentrations of chromatographically purified Serratia marcescens hemolysin (ShlA) caused irreversible vacuolation and subsequent lysis of the cells. Vacuolation differed from vacuole formation by Helicobacter pylori VacA. Sublytic doses of ShlA led to a reversible depletion of intracellular ATP. Restoration to the initial ATP level was presumably due to the repair of the toxin damage and was inhibited by cycloheximide. Pores formed in epithelial cells and fibroblasts without disruption of the plasma membrane, and the pores appeared to be considerably smaller than those observed in artificial lipid membranes and in erythrocytes and did not allow the influx of propidium iodide or trypan blue. All cytotoxic effects induced by isolated recombinant ShlA were also obtained with exponentially growing S. marcescens cells. The previously suggested role of the hemolysin in the pathogenicity of S. marcescens is supported by these data.

Adenosine Triphosphate↗

PubMed1998

The Serratia marcescens hemolysin is secreted but not activated by stable protoplast-type L-forms of Proteus mirabilis.

The outer-membrane protein ShlB of Serratia marcescens activates and secretes hemolytic ShlA into the culture medium. Without ShlB, inactive ShlA (termed ShlA*) remains in the periplasm. Since Proteus mirabilis L-form cells lack an outer membrane and a periplasm, it was of interest to determine in which compartment recombinant ShlA* and ShlB are localized and whether ShlB activates ShlA*. The cloned shlB and shlA genes were transcribed in P. mirabilis stable L-form cells by the temperature-inducible phage T7 RNA polymerase. Radiolabeling, Western blotting, and complementation with C-terminally truncated ShlA (ShlA255) identified inactive ShlA* in the culture supernatant. ShlB remained cell-bound and did not activate ShlA without integration in an outer membrane. Although hemolytic ShlA added to L-form cells had access to the cytoplasmic membrane, it did not affect L-form cells. Synthesis of the large ShlA protein (165 kDa) in P. mirabilis L-form cells under phage T7 promoter control demonstrates that L-form cells are suitable for the synthesis and secretion of large recombinant proteins. This property and the easy isolation of released proteins make L-form cells suitable for the biotechnological production of proteins.

Bacterial Outer Membrane Proteins↗

PubMed1997

Specific phosphatidylethanolamine dependence of Serratia marcescens cytotoxin activity.

The cytolytic and haemolytic activity of Serratia marcescens is determined by the ShlA protein, which is secreted across the outer membrane with the aid of the ShlB protein. In the absence of ShlB, inactive ShlA* remains in the periplasm of Escherichia col transformed with an shlA-encoding plasmid, which indicates that ShlB converts ShlA* to active ShlA. ShlA* in a periplasmic extract and partially purified ShlA* were activated in vitro by partially purified ShlB. When both proteins were highly purified, ShlA* was only activated by ShlB when phosphatidylethanolamine (PE) or phosphatidylserine was added to the assay, while phosphatidylglycerol contributed little to ShlA* activation. Lyso-PE, cardiolipin, phosphatidylcholine, phosphatidic acid, lipopolysaccharide and various detergents could not substitute for PE. Although radioactively labelled PE was so tightly associated with ShlA that it remained bound to ShlA after heating and SDS-PAGE, it was not covalently linked to ShlA as PE could be removed by thin-layer chromatography with organic solvents. The number of PE molecules associated per molecule of ShlA was 3.9 +/- 2.2. Active ShlA was inactivated by treatment with phospholipase A2, which indicated that PE is also required for ShlA activity. ShlA-255 (containing the 255 N-terminal amino acids of ShlA) reversibly complemented ShlA* to active ShlA and was inactivated by phospholipase A2, which demonstrated that PE binds to the N-terminal portion of ShlA; this region has previously been found to be involved in ShlA secretion and activation. Electrospray mass spectroscopy of ShlA-255 determined a molar mass that corresponded to that of unmodified ShlA-255. An E. coli mutant that synthesized only minute amounts of PE did not secrete ShlA but contained residual cell-bound haemolytic activity. Since PE binds strongly to ShlA* in the absence of ShlB without converting ShlA* to haemolytic ShlA, ShlB presumably imposes a conformation on ShlA that brings PE into a position to mediate interaction of the hydrophilic haemolysin with the lipid bilayer of the eukaryotic membrane.

Agar↗

PubMed1996

Disappearing subdural hematomas in children.

Subdural hematomas in infants and young children are uncommon, usually occurring from nonaccidental trauma in infants or from trauma associated with motor vehicles. We report 4 children with apparent unilateral convexity subdural hematomas, 3 of which occurred from household falls and 1 occurring from a fall out of a window. These injuries were characterized by clinical symptoms consistent with the apparent forces involved, which were relatively minor in the first three instances. The clots resolved spontaneously within the first 1-2 days after injury. Such collections are likely located at least partly within the subarachnoid space, but may mimic more clinically significant subdural hematomas. Their recognition may influence decisions regarding both surgical evacuation and the likelihood of nonaccidental injury. Clinical and radiographic features distinguishing these 'disappearing subdurals' from more typical subdural hematomas are discussed.

Accidental Falls↗

PubMed1992

Head injury in very young children: mechanisms, injury types, and ophthalmologic findings in 100 hospitalized patients younger than 2 years of age.

Head injury in the youngest age group is distinct from that occurring in older children or adults because of differences in mechanisms, injury thresholds, and the frequency with which the question of child abuse is encountered. To analyze some of these characteristics in very young children, the authors prospectively studied 100 consecutively admitted head-injured patients 24 months of age or younger who were drawn from three institutions. Mechanism of injury, injury type, and associated injuries were recorded. All patients underwent ophthalmologic examination to document the presence of retinal hemorrhages. An algorithm incorporating injury type, best history, and associated findings was used to classify each injury as inflicted or accidental. The results confirmed that most head injuries in children younger than 2 years of age occurred from falls, and while different fall heights were associated with different injury types, most household falls were neurologically benign. Using strict criteria, 24% of injuries were presumed inflicted, and an additional 32% were suspicious for abuse, neglect, or social or family problems. Intradural hemorrhage was much more likely to occur from motor vehicle accidents and inflicted injury than from any other mechanism, with the latter being the most common cause of mortality. Retinal hemorrhages were seen in serious accidental head injury but were most commonly encountered in inflicted injury. The presence of more serious injuries associated with particular mechanisms may be related to a predominance of rotational rather than translational forces acting on the head.

Accidental Falls↗

PubMedDate not supplied

The intraoperative oculocardiac reflex as a predictor of postoperative vaso-vagal responses during adjustable suture surgery.

1. Adjustable suture surgery has become a popular method of strabismus correction in cases in which results are less predictable, such as reoperations, thyroid ophthalmopathy, and blind eyes. 2. Some adjustable strabismus surgery patients experience significant vaso-vagal responses (V-VR) during postoperative adjustment. 3. A positive intraoperative oculocardiac reflex under general anesthesia during strabismus surgery is highly predictive of a postoperative V-VR during planned adjustment.

Anesthesia, General↗