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Biomedical subjects

M E Howden

Publications and source records attributed to M E Howden.

At least 55 records · Page 3Linked to original sources
PubMed1988

New allergens from hen's egg white and egg yolk. In vitro study of ovomucin, apovitellenin I and VI, and phosvitin.

Three hen egg yolk proteins, apovitellenins I and VI and phosvitin, and one egg white protein, ovomucin, were purified and tested for their ability to bind IgE in the sera of patients hypersensitive to egg. All of the proteins bound IgE from the sera of egg-allergic individuals in the radioallergosorbent test, and they also inhibited binding of IgE to the parent fractions-either egg yolk (apovitellenins I and VI and phosvitin) or egg white (ovomucin). It appears that apovitellenins I and VI are major allergens for some of the individuals tested. This is the first report of the in vitro allergenicity of these proteins.

Allergens↗
PubMed1987

Studies on the subunit structure of textilotoxin, a potent neurotoxin from the venom of the Australian common brown snake (Pseudonaja textilis).

Textilotoxin is a presynaptic neurotoxin from the venom of the Australian common brown snake, Pseudonaja textilis. It has the highest lethality and is structurally the most complex of any known snake venom neurotoxin. It was resolved into its five non-covalently linked subunits in a single step by reverse-phase HPLC. Two of the subunits were identical. The N-terminal amino-acid sequence and amino-acid composition of each subunit were determined. Subunit A was the only one found to possess phospholipase A activity. Separation of textilotoxin into its subunits was reversible and reformed textilotoxin had the same Mr and lethality in mice as the native toxin. Experiments with various unnatural combinations of subunits have led to interesting variations in lethality and Mr of the resulting complexes.

Amino Acid Sequence↗
PubMed1987

Pseudonajatoxin b: unusual amino acid sequence of a lethal neurotoxin from the venom of the Australian common brown snake, Pseudonaja textilis.

The complete amino acid sequence of pseudonajatoxin b, a basic neurotoxin from the venom of the Australian common brown snake, Pseudonaja textilis, was determined by automated Edman analysis of the reduced carboxymethylated polypeptide and of peptides derived by digestion of it with Staphylococcus aureus V8 proteinase. Pseudonajatoxin b consists of a single polypeptide chain of 71 amino acids with Mr 7762. The amino acid sequence showed considerable homology with postsynaptic long neurotoxins, but there were striking differences. Pseudonajatoxin b displayed relatively high lethality, LD50 15 micrograms/kg in mice.

Amino Acid Sequence↗
PubMed1987

Lectins and the radioallergosorbent test.

An investigation into the possible role of lectin binding of IgE in RAST of legume and wheat extracts is reported. Lectins from pea, broad bean, lentil, jack bean, soybean, peanut, and wheat germ were coupled to RAST discs. The discs were pretreated with lectin-specific sugars in an attempt to inhibit RAST with sera from 11 sensitive patients. In all cases, RAST was almost unaffected by the inhibitory sugars, indicating that nonimmune binding of IgE by lectins in legume or wheat RAST was not significant when RAST was carried out with allergens bound to the usual paper discs. IgE contains binding sites for all the lectins examined, and five of the sera had high total IgE greater than 300 IU/ml. It is suggested that competition by IgG and other serum glycoproteins may explain the lack of effect by the added sugars. All sera contained endogenous glucose at a level of about 3 mmol/L that may have accounted for some self-inhibition of the lectin binding by pea, broad bean, lentil, and jack bean lectins. There was, however, significant immune binding of some of the lectins by specific IgE, and it is concluded that these lectins may be important in expression of IgE-mediated allergic responses.

Arachis↗
PubMed1987

Allergenic cross-reactions among legume foods--an in vitro study.

The specific IgE binding by protein extracts of 11 food legumes, including soybean, was examined by RAST and RAST inhibition. Sera from 15 peanut-sensitive patients were, with very few exceptions, positive in the RAST to all the legumes. RAST-inhibition testing of each extract against RAST discs of the other legumes indicated considerable cross-reactivity of IgE binding between the legumes. Cross-allergenicity was demonstrated to be most marked between the extracts of peanut, garden pea, chick pea, and soybean. The results have important implications for selection of effective hypoallergenic diets and for the diagnosis of patients hypersensitive to foods.

Adolescent↗
PubMed1987

Allergenic cross-reactivity of egg-white and egg-yolk proteins. An in vitro study.

The radioallergosorbent test (RAST) and RAST inhibition test were used to examine cross-allergenicity amongst the major hen's egg-white and egg-yolk proteins. Using ovalbumin as a reference allergen to compare cross-reactivity, it was apparent that the proteins conalbumin, ovomucoid and lysozyme substantially inhibited binding to ovalbumin discs of IgE in the sera of patients clinically hypersensitive to egg. The converse situation with conalbumin, ovomucoid and lysozyme on the discs and ovalbumin as the inhibitor also resulted in significantly decreased levels of IgE binding to the proteins on the discs. It was also demonstrated that cross-reactions occurred between ovalbumin and the yolk protein, apovitellenin I. Cross-reaction was also observed surprisingly when egg lysozyme was on the disc and the milk protein allergen alpha-lactalbumin was used as the inhibitor. The demonstration of cross-reaction between all of these proteins may signify that there are a number of common allergenic determinants on these egg proteins, thus providing a molecular basis for the phenomenon of cross-reactivity.

Adolescent↗
PubMed1986

Growth hormone-dependent insulin-like growth factor (IGF) binding protein from human plasma differs from other human IGF binding proteins.

A growth hormone-dependent binding protein for insulin-like growth factors (IGF-I and IGF-II) has been isolated from human plasma. Analyzed on SDS gels, the preparation contained a major protein band of 53 kDa, and a minor band of 47 kDa. After transfer to nitrocellulose, both species bound iodinated IGF-I, and could be detected using an antibody raised against the purified preparation. In contrast, an IGF binding protein purified from human amniotic fluid bound IGF-I but was not detectable immunologically. The amino acid comparison of the plasma binding protein preparation was different from that reported for amniotic fluid and HEP G2 hepatoma proteins, and the unique amino-terminal sequence, Gly-Ala-Ser-Ser-Ala-Gly-Leu-Gly-Pro-Val-, was different from that of the amniotic fluid and hepatoma proteins. This study indicates that the growth hormone-dependent IGF binding protein of human plasma is structurally and immunologically distinct from other IGF binding proteins.

Amino Acid Sequence↗
PubMed1986

Partial characterization of an allergenic glycoprotein from peanut (Arachis hypogaea L.).

A concanavalin A-reactive glycoprotein allergen has been isolated from peanut (Arachis hypogaea). The allergen was separated by affinity chromatography and purified by gel permeation and ion-exchange chromatography. The monomeric molecular weight is 65,000 and the pI is 4.6. The presence of one cysteine residue per molecule results in some dimer formation. Concanavalin A-reactive glycoprotein is a potent allergen for peanut-sensitive patients in both in vivo and in vitro tests. It is allergenically stable, on in vitro examination, at temperatures of up to 100 degrees C and over the pH range 2.8-10. Removal of the carbohydrate moiety failed to eliminate the allergenicity. Concanavalin A-reactive glycoprotein is identified in the crossed immunoelectrophoretic pattern as a major antigen of peanut protein extract but its structural characteristics indicate that it is probably not a component of the major storage-protein complex, arachin.

Allergens↗
PubMed1985

Complete amino acid sequence of a new type of lethal neurotoxin from the venom of the funnel-web spider Atrax robustus.

Robustoxin, the lethal neurotoxin isolated from the venom of the male Sydney funnel-web spider, Atrax robustus, is of unique structural type and physiological mode of action. The primary structure of this 42-residue peptide was determined to be H2N-Cys-Ala-Lys-Lys-Arg-Asn-Trp-Cys-Gly-Lys-Asn-Glu-Asp-Cys-Cys-Cys-Pro- Met-Lys-Cys-Ile-Tyr-Ala-Trp-Tyr-Asn-Gln-Gln-Gly-Ser-Cys-Gln-Thr-Thr-Ile- Thr-Gly-Leu-Phe-Lys-Lys-Cys-H. The disposition of disulphide-bridged cysteine residues at both the amino- and carboxy-termini and as a triplet at residues 14-16 appears to have no precedent amongst neurotoxins.

Amino Acid Sequence↗
PubMed1985

Allergens in the white and yolk of hen's egg. A study of IgE binding by egg proteins.

The radioallergosorbent test (RAST) was used to compare the IgE binding of egg white and yolk, and allergenic proteins were detected by immunoelectrotransfer ('Western blotting'). The main allergens were found in egg white, but for a large proportion of the egg-sensitive patients, yolk contained specific IgE-binding constituents. For blood sera from 36 patients, there was a positive correlation between the results of RAST for egg white and for yolk. Lysozyme was found to be an allergen for some patients. The effect of heating on the allergenicity of egg white was examined and the allergenicity of hen egg white was compared with that of a duck egg. The allergens in yolk were associated with each of the three yolk fractions, and several of the proteins in the low-density lipoprotein fraction bound IgE.

Adolescent↗
PubMed1984

Occurrence of a tetrodotoxin-like compound in the eggs of the venomous blue-ringed octopus (Hapalochlaena maculosa).

A lethal toxin was isolated and partly purified from the eggs of the blue-ringed octopus, Hapalochlaena maculosa. Examination of the toxin by thin layer chromatography, isoelectric focusing and its effects upon the compound nerve action potentials of the toad sciatic nerve gave results that were indistinguishable from those displayed by authentic tetrodotoxin, the toxin present in the venom glands of the octopus.

Action Potentials↗
PubMed1984

A comparative study of properties and toxic constituents of funnel web spider (Atrax) venoms.

The crude venoms of male and female Sydney funnel web spiders, Atrax robustus, were compared by cation-exchange and high-performance liquid chromatography, lethality to new-born mice, polyacrylamide gel isoelectric focusing, immunoelectrophoresis, phospholipase A analysis, effects on the mouse phrenic nerve hemidiaphragm and passive paw oedema in the rat and, except in the case of rat paw oedema, were found to exhibit quite different properties. Polyacrylamide gel isoelectric focusing and high-performance liquid chromatography proved to be suitable for gender and species determination when applied to the venoms of A. formidabilis, A. infensus, A. robustus and A. versutus. These venoms were also compared by lethality, promotion of muscle fasciculation and phospholipase A activity.

Animals↗
PubMed1983

Multiplicity of allergens in peanuts.

Crude peanut protein fractions from raw and roasted peanuts were examined in the RAST with 10 sera from patients showing clinical peanut sensitivity. The radioactive uptake results, which were generally high, did not reveal any distinguishable pattern. Two commercially available peanut proteins, peanut lectin and phospholipase D, gave poor RAST responses. Three purified peanut proteins, alpha-arachin, conarachin I, and concanavalin A-reactive glycoprotein, all gave significant RAST results that were generally lower than those obtained with the crude extracts. The extent of RAST inhibition obtained with these materials was inversely related to their abundance in the total peanut protein. Crossed immunoelectrophoresis with extracts from raw and roasted peanut indicated the presence of 22 and 10 anodically migrating antigens, respectively. Sixteen IgE binding antigens were revealed for raw peanut and seven for roasted peanut after incubation with a mixed serum from the 10 patients in crossed radioimmunoelectrophoresis (CRIE) using 125I-labeled anti-IgE. CRIE plates treated with individual serum samples showed that all the patients had specific IgE for the major antigen peak, which has been tentatively identified as alpha-arachin. This major storage protein of peanut, which is known to be particularly heat resistant; may be of greater clinical significance than its apparently low RAST activity would seem to indicate.

Adolescent↗
PubMed1982

Investigation of the involvement of Echium plantagineum (Paterson's curse) in seasonal allergy. IgE antibodies to Echium and other weed pollens.

The possible allergenicity of an insect pollinated weed, Echium plantagineum, was investigated in a rural area of Australia. Sixty-one subjects with respiratory allergy were studies. Positive skin test reactions to defatted ammonium bicarbonate extract of pollen were found in over 60% of subjects, and positive RAST tests in a similar number. The question of crossreactivity between weed pollens is discussed. The pollen of E. plantagineum was shown to reach the atmosphere in significant amounts about 1 month before the peak grass pollinating period. Evidence that the pollen of E. plantagineum becomes airborne and elicits an IgE response suggests that further attention should be directed to weed pollens as potential allergens.

Adolescent↗
PubMed1982

Allergens from plantain (plantago lanceolata). Studies with pollen and plant extracts.

There has been unjustified neglect of dicotyledonous (dicot; 'weed') pollens in research directed at isolating pure allergens, since dicot pollens are widespread and frequently important in provoking immediate allergic reactions. Sera from patients who showed positive skin prick test reactions to plantain pollen generally also reacted in the radioallergosorbent test (RAST) with at least one other species of dicot pollen. Fractionation of plantain pollen extracts by ultrafiltration and molecular sieving and examination of the fractions by the RAST revealed a spread of allergenic activity. Using crossed immunoelectrophoresis, at least 16 different antigens were detected in plantain pollen and at least 6 of these antigens may be allergenic. Allergenic glycoproteins that react with concanavalin A were isolated and their complexity examined by electrophoresis and electro-focusing. IgE-binding components were found widely distributed in plantain plants and not confined to the pollen.

Allergens↗
PubMed1981

Nonprotein neurotoxins.

Nonprotein neurotoxins are continuing to play a major role as molecular probes in studying nervous processes. They also have clinical importance as some of them, such as saxitoxin and its analogues, are the source of public health problems, or have potential use in therapy. This review covers clinical, biological, pharmacological, and chemical aspects of certain nonprotein neurotoxins, with emphasis on three well-known ones: tetrodotoxin, saxitoxin, and batrachotoxin. The distribution of the toxins is discussed as well as their symptomatology, treatment of affected patients, and effects of their structures on their physiological activity. With so many outstanding problems remaining in neuropharmacology, the study of nonprotein neurotoxins thrives as a fertile area of research.

Animals↗