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M A Olson

Publications and source records attributed to M A Olson.

At least 37 records · Page 2Linked to original sources
PubMed1995

Structural predictions of the channel-forming region of botulinum neurotoxin heavy chain.

A novel combination of theoretical approaches was exploited to predict which amino acid residues of various botulinum neurotoxin serotypes participate in forming ion channels. Estimates of sequence hydrophobic moments were used initially to identify residues within amphipathic regions in the N-terminal half of the heavy chain. A neural network algorithm was then used to make additional secondary structural predictions for these regions. Together, these approaches predicted a complimentary pattern of four, adjacent amphipathic, possibly transmembrane, regions that may be separated by solvent-exposed loops. Both the hydrophobic moment and the neural net analyses predicted that at least one of these amphipathic segments may be in an extended conformation. These theoretical results are discussed in view of our current knowledge of other transmembrane structures.

Algorithms↗
PubMed1995

Cloning and expression of mamba toxins.

Mamba venoms contain pharmacologically active proteins that interfere with neuromuscular transmission by binding to and altering the normal functioning of neuronal proteins involved, directly or indirectly, with regulating nerve transmission. Of the mamba toxins studied to date, many act on voltage-sensitive K+ channels, nicotinic or muscarinic acetylcholine receptors, or acetylcholinesterase. In an attempt to clone, characterize, and express the genes encoding these toxins, as well as other genes specifying activities not completely elucidated as yet, a cDNA library was constructed from mRNA isolated from the glands of the black mamba. Clones from the library harboring sequences encoding 14 different mamba toxins were isolated and characterized by nucleotide sequence analysis. Genes coding for three proteins, dendrotoxins (DTX) K, I, and E, were expressed as maltose-binding (MBP) fusion proteins in the periplasmic space of Escherichia coli. The DTXK-MBP fusion protein was affinity purified, cleaved from its chaperon, and the recombinant DTXK purified from MBP. Recombinant DTXK was shown to be identical to native DTXK in its N-terminal sequence, chromatographic behavior, convulsion-inducing activity, and binding to voltage-activated K+ channels in bovine synaptic membranes. Computer modeling was employed to create three-dimensional structures of DTXK and DTX1 from the X-ray crystal structure of alpha-DTX utilizing both structural and sequence homologies. Comparisons were made between the three toxins, providing a framework for site-directed mutagenesis.

Amino Acid Sequence↗
PubMed1995

Bacterial superantigens in human disease: structure, function and diversity.

All bacterial superantigens use common structural strategies to bind to major histocompatibility complex class II receptors, while binding the T cell antigen receptor in different ways. Overstimulation of the immune response is responsible for the acute pathological effects, while reactivation of developmentally silenced T cells might result in autoimmune disease. Certain diseases might be controlled with superantigens or genetically attenuated vaccines.

Adjuvants, Immunologic↗
PubMed1995

Staphylococcal enterotoxins A and B share a common structural motif for binding class II major histocompatibility complex molecules.

A comparative site-directed mutagenesis study of staphylococcal enterotoxins A and B was undertaken to identify key amino-acid residues which govern interactions with major histocompatibility class II molecules. This involved generating a three-dimensional homology model for enterotoxin A in complex with the HLA-DR1 molecule, based on the reported X-ray crystal structures of enterotoxin B, both free and bound to HLA-DR1. A binding motif previously described for enterotoxin B was found to be conserved in enterotoxin A. An examination of the experimental data with the homology model clarifies how T-cell responses to enterotoxin A, and most bacterial superantigens, are likely to be mediated by variations of a structurally conserved HLA-DR alpha binding motif.

Amino Acid Sequence↗
PubMed1994

Characterization of monoclonal antibodies against Naja naja oxiana neurotoxin I.

Seven monoclonal antibodies (mAbs) were developed against neurotoxin I (NT-1), a protein from central Asian cobra (Naja naja oxiana) venom which binds specifically to nicotinic acetylcholine receptor (AchR). All of the mAbs cross-reacted with another long-chain post-synaptic neurotoxin, Bungarus multicinctus alpha-bungarotoxin (alpha-BT), but not Naja naja kaouthia alpha-cobratoxin, in an enzyme-linked immunosorbent assay (e.l.i.s.a.). Short-chain post-synaptic neurotoxins like Naja naja atra cobrotoxin, Laticauda semifasciata erabutoxin b, or N. n. oxiana neurotoxin II did not cross-react with the NT-1 mAbs, but an antigen(s) found in Dendroaspis polylepis, Acanthophis antarcticus and Pseudechis australis venoms was immunoreactive. The e.l.i.s.a. readings for dithiothreitol-reduced NT-1 and NT-1 mAbs ranged from 13 to 27% of those for native toxin but reduced alpha-BT was not immunoreactive. Synthetic NT-1 peptides were used in epitope-mapping studies and two, non-contiguous regions (Cys15-Tyr23 and Lys25-Gly33 or Pro17-Lys25 and Asp29-Lys37) were recognized by the NT-1 mAbs. The NT-1 mAbs individually inhibited 31-71% of alpha-BT binding to AchR in vitro and afforded a slight protective effect in vivo with a toxin: antibody mole ratio of 1:1.5. This report is the first to describe mAbs which recognize and protect against a heterologous, long-chain, post-synaptic neurotoxin from snake venom.

Amino Acid Sequence↗
PubMed1994

Secondary structural predictions for the clostridial neurotoxins.

The primary structures of a family of ten clostridial neurotoxins have recently been deduced yet little information is presently available concerning their secondary or tertiary structures. Because the overall similarity percentage of multiply aligned sequences is high, the secondary structures of these metalloendopeptidases are also expected to be conserved. The neural net program, PHD (Rost and Sander, Proc. Natl. Acad. Sci. USA 90:7558-7562, 1993), predicted that the secondary structures of the neurotoxins were indeed conserved in both single and multiple sequence modes of analysis. Predictions for the amounts of helical, extended, and loop states from the single sequence analyses were consistent with previously published data from circular dichroism studies on some of these neurotoxins. In the single analysis mode, only the aligned regions were predicted to show conservation of the three-state structure. In contrast, the multiple sequence analysis predicted that a conserved state (variable loops) also exists in non-aligned regions. Alignments with the primary structure of the prototypic metalloendopeptidase thermolysin showed that about 25% of the residues within this enzyme are similar to those in the neurotoxins. A comparison of thermolysin's known secondary structure with the predictions from this study showed that about 80% of thermolysin's residues could be structurally aligned with those in the neurotoxins. These predictions provide the necessary framework to build a homologous low-resolution tertiary structure of the neurotoxin active site that will be essential in the development of synthetic inhibitors.

Amino Acid Sequence↗
PubMed1993

Susceptibility of first instar Toxorhynchites splendens to malathion, naled and resmethrin.

Acute toxicity tests were conducted to measure the response of first instar Toxorhynchites splendens to commonly used mosquito adulticides: malathion, naled and resmethrin. The concentrations of pesticide causing 50% mortality (LC50) after 24 h was 2.87, 69.1 and 623 ppb for resmethrin, malathion and naled, respectively. Naled was determined to be the least toxic of the 3 compounds tested for integrated use with Tx. splendens. The latter assessments were based on comparisons between laboratory-derived dose-response curves and maximum concentrations reached in standing water calculated using standard application rates.

Animals↗
PubMed1993

Tolerance of sewage treatment plant microorganisms to mosquitocides.

Beneficial protozoa and rotifers collected from a wastewater treatment plant in Panama City, FL, were tested for tolerance to 11 commonly used mosquito larvicides and adulticides in the laboratory. The acute effects were assessed using selected concentrations of the adulticides fenthion, malathion, naled, permethrin, and resmethrin; and the larvicides Bacillus thuringiensis israelensis, Bacillus sphaericus, diflubenzuron, larviciding oil, methoprene, and temephos for the following microorganism taxa: ameoboids, flagellates, free-swimming ciliates, stalked ciliates, and rotifers.

Animals↗
PubMed1991

Acute toxicity of mosquitocidal compounds to young mosquitofish, Gambusia affinis.

Toxicity of Florida mosquito larvicides and adulticides to 3-5 day old Gambusia affinis was determined in the laboratory. After 24-h exposure, the larvicides, temephos, fenoxycarb and petroleum distillates had LC50 values of 5.60, 1.05 and 593.4 ppm, respectively. After 24 h the adulticides resmethrin, fenthion, naled and malathion had LC50 values of 0.007, 2.94, 3.50 and 12.68 ppm, respectively. The only compound toxic to young mosquitofish at maximum field application rates was resmethrin. However, in the light of earlier tests, aerially applied adulticides generally reach the water surface at reduced concentrations and thus probably pose little or no risk to mosquitofish populations.

Animals↗
PubMed1991

Effects of Arosurf MSF on a variety of aquatic nontarget organisms in the laboratory.

Ninety-six-hour static acute toxicity tests were conducted in the laboratory to determine the effects of a 47 ml/m2 (50 gal/acre) application of Arosurf MSF (2 mole ethoxylate of isostearyl alcohol) on Fundulus similus, Palaemonetes pugio, Palaemonetes paludosus, Uca spp., Procambarus spp., Gammarus spp., Asellus spp., Streptocephalus seali, Physa spp., Laeonereis culveri and an unidentified amphipod. Test temperatures of 20-27 degrees C were based on the ambient water temperature for the season of the year when the desired life stages were more abundant. No acute toxicity was observed with any of the organisms exposed to this concentration of Arosurf MSF.

Animals↗
PubMed1986

The Scimitar syndrome: CT findings in partial anomalous pulmonary venous return.

An anomalous pulmonary vein draining into the subdiaphragmatic inferior vena cava was initially demonstrated on computed tomographic (CT) scans. The diagnosis of scimitar syndrome was confirmed with digital subtraction angiography. In retrospect, the anomalous vein and dextroposition of the heart were shown on chest radiographs.

Female↗
PubMed1986

Impact of myelography on the radiotherapeutic management of malignant spinal cord compression.

From December 1981 through August 1984, 24 patients with spinal cord compression syndrome due to epidural neoplasms were evaluated for radiotherapy with clinical examination, radiographs of the spine, and myelography. All plain films were reviewed, and mock radiotherapy fields designed using specific criteria for margins. The same patients were reviewed a second time considering the additional information provided by myelography. The initial treatment fields were found to be inadequate in 69% of the patients. Even in patients with discrete bony lesions, the results of myelography affected the treatment 45% of the time. A history of previous spinal irradiation significantly influenced port design in only 1 of the 7 patients who had received previous radiotherapy. Although invasive, myelography is essential in planning the treatment of spinal cord compression.

Adult↗
PubMed1984

Seasonal arsenic exposure from burning chromium-copper-arsenate-treated wood.

All eight members of a rural Wisconsin family experienced recurring neurological and medical illness over three years, especially during the winter months. Arsenic, in concentrations of 12 to 87 ppm, was noted in the hair of the mother and father, and analysis of hair and fingernails of all family members demonstrated pathological levels of arsenic. For four years the five-room home had been heated with a small wood stove in which outdoor or marine plywood and wood remnants had been preferentially burned. Stove ashes that contained more than 1,000 ppm of arsenic contaminated the living area, and the ratio of copper, chromium, and arsenic pentoxide in this ash matched the ratio used in the chromium-copper-arsenate-treated wood.

Adolescent↗
PubMed1983

Food, drugs, and alcohol--a common temporal pattern of use.

Two samples of college students (n = 42) in a weight-control program were shown to deviate from their diets in a temporal pattern found in previous studies for the abuse of street drugs and alcohol. Implications for the treatment of various types of substance abuse and eating disorders are discussed.

Adolescent↗